Rice Production: Chapter 9 - Fertilizer sources and management

Introduction

Many rice varieties, particularly the high-yielding improved varieties currently being introduced into many traditional farming systems throughout the world, respond markedly to fertilization. When used in conjunction with good management practices (thorough land preparation, controlled irrigation, timely weeding) fertilizers can increase yields many times over. On the other hand, if used improperly fertilizers can damage crops, waste money, or possibly lead to a dependence on scarce chemical inputs. In many developing areas fertilizers are still unknown or poorly understood, and the extension agent represents the farmer's only source of information about safe, economical, and effective fertilization practices.

This chapter describes the most common sources of fertilizer and outlines a recommended application schedule for irrigated rice. Included are practical suggestions for effective handling, application, and storage of chemical fertilizers.

I. Fertilizer Sources 

A. Organic Fertilizers

Organic fertilizers are decomposed remains of plants and animals. In the natural ecosystem, elements absorbed from the soil by living organisms are returned to the soil through decay and decomposition following the death of the organisms. Organic fertilizers traditionally have provided all of the nutrients in shifting agriculture systems where periods of cultivation alternate with fallow periods (during which the natural regenerative process restores organic fertilizers to the soil). Organic fertilizers also have traditionally provided most nutrients to swamp farming systems, since swamps serve as natural catchments for organically derived nutrients which wash down off the surrounding uplands.

The introduction of improved rice varieties into a traditional swamp farming system tends to create a situation here the nutrient demands of the crop outstrip the natural ability of the ecosystem to replenish its organic resources. Although knowledgable swamp farmers can exploit the natural regenerative properties of many so-called "waste" products to help maintain soil fertility (e.g. by incorporating organic material back into the soil), and although they can replenish nutrients by planting nitrogen-fixing legumes during part of the year, repeated high yields will inevitably extract greater amounts of some nutrients particularly nitrogen, phosphorus, and potassium - than can rapidly be returned to the soil through the use of organic fertilizers or alternate cropping practices. Thus, the swamp farmer is faced with a decision. Either s/he opts for a balanced farming system which will be able to sustain medium yields over a long period with minimal chemical inputs. Or s/he elect to try for the highest possible yields - which in most cases means relying on inorganic fertilizers.

B. Inorganic Fertilizers

Inorganic fertilizers are chemical compounds (either synthesized natural) which are added to the soil to improve fertility. The most important characteristics of inorganic fertilizers are that they can be extremely economical can vastly increase yields land can result in significant profits), and they are fast-acting (since the nutrients they contain are immediately available to the crop and do not have to be processed by microbes in the soil).

Depending on their chemical composition, inorganic fertilizers may contain only one nutrient or several:

Single-element fertilizers contain only one of the primary nutrient elements (N,P, or K)

Incomplete fertilizers contain two of the three primary nutrient elements (N and 1, N and K, or P and K) Complete fertilizers, contain all three of the primary nutrient elements (N,P, and K)

It is important to remember that inorganic fertilizers always co:., + of the nutrient element (s) bonded to can inert "carrier'. Consequently the total weight of the fertilizer does not correspond exactly to the weight of the nutrient it contains: the weight of the nutrient comprises only a part of the total fertilizer weight and varies according ding to the chemical composition of the fertilizer. For example: one 100 lb bag of ammonium sulphate ( 20% N) contain 20 lbs nitrogen and 80 lbs of inert material, while one 100 lbs bag of urea 45% N) contains 45 lbs nitrogen and 55 lbs of inert material. In terms of its ability to supply nitrogen en, urea is therefore more than twice as "strong;" as ammonium sulphate because it contains more than twice as much nitrogen of by weight.

Listed below are the fertilizers most commonly used in Sierra, a Leone ( fill in current prices ):

1 Single-element fertilizers

Ammonium sulphate 20% N)	Price:
Urea ( 45% N)	Price:
Single superphosphate ( 18% P2O5)	Price:
Basic Slag ( 14.5% P2O5 )	Price:
Muriate of Potash ( 60% K2O )	Price:
sulphate of Potash (50% K2))	Price:

2) Incomplete Fertilizers

N-P-K 20-20-0 (20% N, 20% P2O5, 0% K2O )	Price:
N-P-K 0-20-20 ( 0% N, 20% P2O5, 20% K2O )	Price:

3) Compete fertilizers

N-P-K 15-15-15 (15% N, 15% P2O5 15% K2O)

Price:

Notes on fertilizer storage:

Great care should be taken in handling, transporting, and storing chemical fertilizers. Although most inorganic fertilizers are fairly inert when kept dry, many undergo drastic chemical changes when exposed to rain or even moisture in the air. The resulting gases and liquids not only carry off valuable nutrierits, but they car cause considerable corrosive damage to cement floors and wall, metal tools, motorcycles, etc.

It best to store chemical fertilizers by themselves in a dry, well ventilated room. Be sure to keep the bags off the floor (use wooden pallets to elevate them) and stack them so that air can circulate between the bags. Avoid storing food, seed rice, or pesticides nearby.

Take the time to construct a proper fertilizer-tore. Improper storage can Present a safety hazard and decrease the power of the fertilizer.

II. Fertilizer Management

There is no single recommendation for rice fertilization which will fit all situations. Fertilizer application will vary considerably, depending on crop requirements, the availability of fertilizers, the financial resources of the farmer, and most importantly, the ability of the farmer to follow application schedules (some of which can be quite complicated).

Tests and field experience have shown that the application of 40 kg/ha (36 lbs/acre) each of nitrogen phosphorus, and potassium gives optimum results under most local conditions. (Important: that's 40 kg/ha of nutrient, not of fertilizer.) 40 kg/ ha is the generally recommended application rate. Of course many farmers will be either unwilling or unable to purchase this amount of fertilizer, arid they will end up fertilizing at a much lower rate (or not at all). Decreasing the amount of fertilizer will result in more modest yields, but keep in mind that any amount of fertilizer, no matter how small, will help. If a farmer deeds to fertilize but can afford only one bag of N-P-K 15-15-15 per acre, don't necessarily discourage him/her If applied properly, even this relatively small amount of fertilizer will affect favorable results.

Timing Fertilizer Applications

For optimum results, fertilizer should be applied to the soil at three points in the crop cycle:

1) The Basal Application

Just prior to transplanting, fertilizer should be broadcast and puddled into the sell to ansure an abundance of nutrients during the critical seedling establishment phase. The basal application facilitates the plant's rapid recovery from the shock of transplanting. If possible, all phosphorus should be applied basally, since root development is crucial at this time.

2) First Top Dressing

When the seedlings have fully recovered from the shock of transplanting and have entered into the active tillering stage (approximately two weeks after transplanting for most varieties), fertilizer should be broadcast and puddled into the soil. This operation can be combined with the first weeding. The first top dressing ensures rapid vegetative growth, promotes tillering, and helps strengthen the plants against disease attack. Nitrogen and potassium should be applied with the first top dressing.

3) Second Top Dressing

Immediately after panicle initiation (the date will vary according to the duration of the variety), fertilizer should once again be broadcast and puddled into the soil. The second top dressing ensures complete grain filling, increases the size and weight of the grains, and improves the quality of the crop by increasing the protein content. Nitrogen and potassium should be applied with the second top dressing.

An ideal fertilization schedule thus might look something like this:

Day of transplanting -	Basal Application
	40 kg/ha phosphorus
Active tillering -	First Top Dressing
	20 kg/ha nitrogen
	20 kg/ha potassium
Panicle initiation -	Second Top Dressing
	20 kg/ ha nitrogen
	20 kg/ha potassium

HOWEVER: it is possible that many farmers will have neither the means nor the ability to adhere closely to such a schedule. Often you will find yourself working with smaller amounts of fertilizer, or with only one incomplete or complete fertilizer instead of several single-element fertilizers. Expect to adjust this application schedule to the requirements of each situation - "go with the flow." You may want to devise a separate schedule for each farmer; do the best you can to get the nutrients to the rice when they will be needed most.

Some tips on applying fertilizers:

- It is sometimes difficult to broadcast small amounts of fertilizer over a relatively large area. Since uneven distribution of nutrients is ineffecient and in some cases actually harmful to the rice, remember that fertilizer car; always be stretched by the addition of an inert filler such as dirt or sand.

- Never broadcast nitrogenous fertilizers (ammonium sulphate, urea, N-P-K) onto standing water. Upon contact with water, the ammonium ions are converted to ammonia gas, and much nitrogen is lost into the air. Broadcast all top dressings onto drained plots and then puddle in the fertilizer by hand before re-flooding.

- Be sure that water does not flow out of recently fertilized plots. Water carries off nutrients!

- Always be aware of safety considerations. Try to avoid fertilizing in swamps from which water is used for drinking, washing, or laundering, unless an alternative water source is available. Helping dig a well or construct a water system is one of the most beneficial secondary projects you can undertake with the farmers in your community.

Additional thoughts on fertilizers:

Although it is tempting for all of us as agriculture extension agents to attempt to sell farmers on the use of fertilizers, we must always be careful not to present a distorted picture of nothing but higher yields. The potential benefits of fertilizer use should be described only in the context of the potential costs: possible dependency and possible safety hazard. Above all, if farmers are to be taught to use chemical fertilizers, they should be taught to use them efficiently, safely, and in moderation. It is unwise to encourage a heavy reliance on inorganic fertilizers in an era when the spiralling price of petroleum products (and many fertilizers are petroleum by-products) theatens to make widespread use of fertilizers uneconomical. When working with fertilizers, try always to remain aware of the fine line between the use of fertilizers to enhance yields and total reliance on them.

III. Fertilizer Calculations

There are a number of variables to consider when calculating the amount of fertilizer to be applied to a given area. These include:

- the percentage of nutrient contained in the fertilizer being used

- the desired rate of application

- the size of the area to be fertilized

In addition, because most farmers do not have access to an accurate scale or balance, it will often be necessary to devise a simple means of converting amounts of fertilizer into a common volume measurement (e.g the 8 oz. cup)

The extension worker can attack the problem of calculating fertilizer for farmers in a number of ways, depending on the degree of accuracy desired. Described below are two approaches to the problem which have proven useful in the past in Sierra Leone.

1) The Rough - and - Ready Method

The simplest method of determining a farmer's fertilizer needs is to calculate how many bags of fertilizer will be needed for the entire swamp and then to divide the swamp and the fertilizer into smaller units at the time of application to ensure a relatively even distribution. First, measure the entire swamp and calculate its area. Practiced field workers can sometimes make an approximate guess at a swamp's area, but make sure the practice at measuring precedes the guessing. Choose the fertilizer you will use - or in most cases, assess what is available. Using the recommended rate of 40 kg/ha, calculate the amount of fertilizer required with this formula:

W = (A x R) / P where

W = weight of the fertilizer to be applied (this is what you are calculating)

A = area to be fertilized (hectares or acres)

R = desired rate of application (in this case the recommended rate, or 40 kg/ha)

P = percentage of nutrient contained in the fertilizer

Example:

You have measured a farmer's swamp to be approximately 1.5 ha. How many bags of urea will be required to fertilize the entire swamp with nitrogen at the recommended rate?

Using the formula W = (A x R) / P where:

W = ?

A = 1.5 ha

R = 40 kg/ha

P = 45% or 45 (determined from the fertilizer chart)

then

W = 1.5 ha x 40 kg/ha / 0.45

W = 60 kg / 45

W = 133.33 kg

W = approximately 130 kg urea

Each bag of urea weighs 50 kg; therefore, to convert 130 kg into bags, divide 130 kg by the weight of one bag:

130 kg = 130 kg / 50 kg = 2.6 bags

The problem now is to ensure that the 2.6 bags of urea get distributed evenly over the 1.5 ha swamp. Try dividing the swamp into ten small sections. Then get together with the farmer and, using a local unit of measure, divide the fertilizer into ten equal piles. Make certain that the farmer understands exactly what you are doing together, because in the future s/he will be doing the same operation without your assistance, Above all, keep things simple.

2) The Fertilizer Tables

Developed swamps are divided into plots smaller than a hectare, acre, or even half acre. A more exact method of calculating fertilizer applications is by the individual plot. This method lends itself well to swamps in which management practices have reached a more sophisticated level, or in which only a few plots are planted at a time.

Then simply multiply this figure - the multiple of the standard area - by the figure appearing in column 6 (since we are working in English measurements here) to determine the cups of basic slag needed:

2.5 x 4.8 = 12 cups of basic slag

Now suppose the farmer checks the storeroom and discovers that there is no more basic slag. But there is a quantity of another phosphoric fertilizer - single superphosphate. How many cups will be needed to fertilize the plot at the recommended rate with single superphosphate?

Since you have already measured the area of the plot and calculated the multiple of the standard area - and recorded this information on a map of the swamp - a quick reference to the fertilizer tables will enable you to determine how many cups of single superphosphate will be needed.

Multiply 2.5 (the multiple of the standard area) by the figure appearing in column 6 opposite the line marked "single superphosphate":

2.5 x 7.4 = 18.5 cups of single superphosphate

The use of the fertilizer tables requires a detailed area survey and a fair amount of math. However, the survey need be performed only once, since the measurements and plot area calculations can be preserved for future reference on a sketch map. The same map can later be used for a number of different purposes: fertilizer calculations, seed requirement calculations, pesticide calculations, and yield comparison.

How to use the tables The columns in the table are as follows:

column 1 - name of the fertilizer

column 2 - number of 8 ounce cups (filled to overflowing) in one 50 kg bag

column 3 - weight of the fertilizer in one cup in grams/(ounces)

column 4 - weight of the nutrient in one cup in grams/(ounces)

column 5 - number of cups needed to fertilize 100 m2 at the recommended rate of 40 kg /ha column 6 - number of cups needed to fertilize 1000 f² at the recommended rate of 36 lbs/acre

If the area of the plot to be fertilized is known, columns 5 and 6 will enable you to calculate rapidly the amount of fertilizer necessary to fertilize at the recommended rate. Simply divide the known area of the plot by 100 m² (if you are using metric measurements) or by 1000 f² (if you are using English measurements) to get a multiple of the standard area used in column 5 and column 6. (Be careful to keep to the same system metric or English, throughout each calculation.) Then multiply this figure - the multiple of the standard area -by the figure appearing in either column 5 or column 6 (whichever 1; appropriate for the units of measurement you are using) to determine the number of cups of fertilizer needed to fertilize at the recommended rate.

Example:

You have measured a plot to equal 2500 f². You want to make a basal application of phosphorus using basic slag as the source of F. The desired rate of application is 36 lbs/acre. How many 8 ounce cups of fertilizer are needed?

First, divide the plot area (2500 f²) by 1000 f² to get a multiple of the standard area:

2500 f² / 1000 f²= 2.5

FERTILIZER TABLES

Note: one cup = 8 ounces

Figure

Rice Production: Chapter 8 - Plant nutrients and effect on growth

Introduction

The growth of the rice plant in any medium (soil, sand, water) depends on the availability of sunlight, water, and various chemical elements. Sixteen elements are recognized as essential in rice nutrition: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, copper, boron, zinc, molybdenum, chloride. Among these, carbon, hydrogen, and oxygen are absorbed directly out of the air and water; the rest must be present in the soil.

Three elements, the so-called primary elements - nitrogen, phosphorus, and potassium - are ingested by the rice plant in unusually large quantities and are therefore particularly important in producing a high yield. This chapter provides a brief, non-technical outline of the role outline of the role of nitrogen, phosphorus, and potassium in the growth of the rice plant.

Note: In considering the effects of individual elements, the relative amounts of other elements present is important for example, nitrogen alone produces certain effects, but the effects may be quite different if there is a proper balance between nitrogen, phosphorus, potassium, and other elements. 

The chemical form in which a nutrient element is present in the soil is also important, since the availability of a nutrient to the plant varies with the roots ability to extract the nutrient element from the chemical compound in which it occurs

I. Nitrogen

Rice grown under high management requires large amounts of nitrogen (n) One crop consumes approximately 20-25 kg of nitrogen for every ton of yield, making nitrogen the single most important rice nutrient. Nitrogen's fundamental importance as a primary nutrient element is augmented by the fact that many improved rice varieties cultivated around the world have been bred to show a marked response to the application of nitrogenous fertilizers.

Nitrogen increases the vigor and enhances the growth of the rice plant. When absorbed during the vegetative phase, nitrogen:

- helps synthesize the chlorophyll necessary for photosynthesis (as evidenced by a marked "greening" of the leaves)

- promotes rapid leaf, stem, and root growth (as evidenced by an increase in the height, size, and number of tillers, as well as an increase in the size of leaves)

- speeds growth, thus enabling seedlings to grow fast enough to avoid many seedling blights

When absorbed during the reproductive and ripening phases, nitrogen:

- promotes development of the panicle (as evidenced by an increase in the number of spike-lets)

- stimulates nutrient absorption and assimilation ( as evidenced by an increase in size and number of filled grains

- increases the protein content of the grains, thus improving the quality of the crop

Nitrogen deficiency in rice can be recognized by:

- yellowish, color of the leaves, particularly of younger leaves

- small size of plants

- low number of tillers

- straightness, stiffness Or upper leaves

II. Phosphorus

Like all cereal grains rice requires a considerable amount of phosphorus (P) for vigorous growth and high yield.

Although in general response -to phosphorous in irrigated rice i<; less marked than response to nitrogen, phosphorus is none the less a very important nutrient - one crop consumes approximately 15 kg of phosphorous for every ton of yield.

Phosphorus is particularly important to the rice seedling d ring the time it is recovering from transplanting shock. Phosphorus greatly stimulates root development in the young plant, thus increasing its ability to absorb nutrients from the soil.

When absorbed during the vegetative phase, phosphorus:

- increases the number of root hairs, thus facilitating the uptake of other nutrients (enables the seedling to recover rapidly from transplanting shock)

- stimulates extensive root growth, thus increasing the plant's resistance to drought

- promotes tillering by facilitating nitrogen absorption - promotes early flowering and ripening (can be exploited to offset the effects of late planting)

During the reproductive phase, the phosphorus intake of rice decreases considerably.

When absorbed during the ripening phase, phosphorus:

- increases the protein content of the grains thus improving the food value of the crop invigorates the germination power of the seed (as evidenced by an increase in the germination rate of the seed produced)

Phosphorus deficiency in rice can be recognized by:

- small size of plants

- short, underdeveloped root systems

- low number of tillers

- bluish green color of the leaves

- purple color of the lower part of the culms (Note some traditional varieties have net rally purple culms.)

III Potassium

Because of the presence of potassium (K) in most irrigation water, the response of rice to potassium is often not as marked as the responses to nitrogen and/or phosphorus, except in unusual situations (e.g. when certain toxicities are offset by potassium). Nevertheless, potassium should not be overlooked as an important nutrient element, since each crop requires approximately 15 kgs. of potassium for every -ton of yield.

When absorbed during the vegetative phase, potassium:

- strengthens cell walls, thus making the plant physically stronger and enabling it to withstands the adverse effects of bad weather

- increases the plant's resistance to penetration by disease organisms

When absorbed during the reproductive and ripening phases potassium:

- increases the plant's resistance to diseases affecting the panicle and grains

- increases the protein content of the grains, thus improving the quality of the crop

- increases the size and weight of the grains

Potassium deficiency in rice can be recognized by:

- deep, dark color of the leaves (spreading from the tips)

- irregular dead spots on the leaves and panicles

- droopiness of leaves, resulting in reduced photosynthesis and consequent slower growth

- unusual susceptibility to disease and pest attack

Rice Production: Chapter 7- Land preparation

Introduction

The yield of a crop of rice is dependent upon many obvious factors: irrigation, fertilization, weeding, pest and disease control. One of the less obvious but equally important factors is land preparation. Because proper land preparation promotes a good environment for seed/soil contact (which will promote rapid crop growth while reducing competition from weeds), it is imperative that land preparation be thorough and timely. This chapter describes and justifies the steps necessary to prepare lowland soil for a successful growing season.

I. Brushing and Clearing

Bard preparation in inland valley swamps begins with a through brushing and clearing Encourage the farmer to begin with the larger stumps and bushes, since grasses and other weeds grow back very quickly and are best left until just before the first plowing. Bushes and tree limbs should not be left to overhang the edges of the paddies. Rice does not grow well in the shade and insects thrive in cool, moist areas. The initial brushing and clearing should be completed about one month before planting.

II. Repairing Water Control Structures

Next, clean and repair all water control structures - irrigation gutters, drains, and sluice gates. Remove weed that have grown in the channels and dig out accumulated silt and clay. The flow of water through the channels is impeded by weeds and sediment, and their capacity is greatly reduced. Repair dikes that may have eroded, paying particular attention to the headband and peripheral (irrigation) gutters. Check all sluice gates for signs of wear; if any threaten to wash out, repair them now. Remember: it is always easier to make repairs and alterations to the water control system before you plant. 

III. Plowing and Puddling

After the water control structures have been cleaned and repaired, plowing may begin. Flowing is done in inland valley swamps for several reasons:

- Weed Control (weeds are destroyed and prevented initially from competing with rice seedlings)

- Incorporation of Organic Matter (weeds and crop residues such as straw and stubble are incorporated into the soil, where they become converted into plant nutrients through decay)

- Transformation of Surface Soil into a Puddle (for ease in transplanting)

- Establishment of a Reduced Zone (increases the availability of some nutrients by maximizing contact between rice root hairs and soil particles)

- Levelling (during plowing the soil can be moved around until the plots are level, thus improving water control)

- Formation of a Flow Pan (repeated plowing to a certain depth will create an impervious hard layer, or plow Far., which will reduce water losses and mineral losses through leaching)

To be most effective, plowing must be done thoroughly and timed properly. In inland valley swamps, the ideal schedule calls for two plowing and one puddling. Timing these operation correctly is very important.

1) First Plowing

The first plowing, or deep plowing, should be completed 2-3 weeks before transplanting begins. There are several reasons for such an early start:

- to protect seedlings against the adverse effects of harmful substances generated by decomposing organic materials

- to allow seedlings to utilize the nitrogen rich ammonium (NH4) released during the decomposition process

- to spread out the work load for the farmer (thorough plowing is very hard work and is best done a little bit at a time)

Flood the plot for several Jays before plowing to soften the soil and make the work easier. On the day of plowing, drain off excess water. Using a hoe or shovel, turn the soil to a depth of 15-20 cm (6"-8") Begin near the edges of the plot (so you can repair the bunds if necessary) and work toward the center. Keep the plot flooded after the first plowing until transplanting. If the plot is allowed to dry out, 20-700 kg of valuable nitrogen could be lost into the air through a process known as denitrification depending on the soil, its previous cropping history and other factors. Note: Many farmers will at first be reluctant to plow 2-3 weeks in advance of transplanting. The traditional practice in many areas is to wait until the seedlings are nursed and almost ready to plant before starting to plow. Encourage farmers to complete the first plowing before parsing their rice. The 2-3 week lead time will give the organic matter sufficient time to decompose, and the toxic substances released during organic matter decomposition will dissipate before the seedlings are planted.

2) Second Plowing

The second plowing should take place 7-10 days after the first plowing. Break up the softened clumps of soil and incorporate straw, stubble, and weeds that may have germinated. Remove large roots that will not decompose, as well as large stores. Lower the water level in the plot during the second plowing to reveal high spots which will need to be leveled. Re-check the water control system and make minor adjustments as needed.

3) Puddling.

Puddling should take place,-10 days after the second plowing and one day before transplanting. Puddling is usually done with bare feet (and draft animals, in areas where they occur). Bush poles are often used to help maintain balance and to break up remaining soil clumps. Puddling further incorporates germinating weeds, facilitates levelling, and breaks down the soil structure into a soupy mud suitable for transplanting. If a basal application of fertilizer is intended, broadcast the fertilizer just before puddling so that it will be well mixed into the soil. After puddling, the soil will be ready for transplanting.

IV. Methods of Plowing

Flowing may be accomplished in several ways:

- plowing by tractor is generally rot suited for inland valley swamps because tractors cannot move easily from plot to plot without destroying water control structures. Furthermore, in flooded soils tractors often are simply too heavy. Initial cost and operating costs are high.

- plowing by roto-tiller (2-5 horsepower) is gaining acceptance in many parts of the world, despite high initial cost and maintenance problems. In broad swamps with large plots, the roto-tiller can be extremely effective and economical. Roto-tillers cannot be used in recently-developed swamps containing many stumps and large roots.

- plowing by animal is extensively practiced with excellent results in most of Asia, but less frequently in Africa (where the se of draft animals is less widespread in general). Most

- draft animals are able to work only 3-4 hours per day without supplementary feeding, end they require considerable care.

- plowing by hand, though tedious and time-consuming, is the major method of plowing inland valley swamps throughout most of Africa. Hand plowing requires the farmer to spend many hours standing in water and thus facilitates the spread shistosomiasis.

Rice Production: Chapter 6 - Methods of stand establishment

Introduction

Two methods of stand establishment - broadcast sowing and transplanting - are widely practiced in Sierra Leone. This chapter describes both methods and includes summaries of the advantages and disadvantages of each.

I. Broadcast Sowing

a) Traditional: 

Most traditional upland farms in Sierra Leone are sown by Broadcasting of ungerminated or germinated seed at the beginning of the rainy season Seed is scattered by hand at a rate of 80-120 kg/ha in soil that has been burned over, cleared, and turned with the native hoe. Usually kitchen crops are mixed in with the rice - beans, millet, sorghum, tomatoes, corn, okra, sesame pumpkin, and watermelon are the preferred varieties. The seed is covered by hoe, rake, or spike-tooth harrow. Traditional broadcast sowing i fast and labor-saving, making it particularly well suited to large upland farms. However, traditional broadcast sowing has several marked disadvantages:

- germination rates are often uneven, due to the reliance on rain
- heavy rains can dislodge and wash away seeds, resulting in uneven seedling stands
- seeds are exposed to rat and bird attack
- broadcast seedlings do not compete favorably with woods
- broadcast seedlings are difficult to weed

b) Improved (Direct Seeding):

In area., where irrigation water is plentiful and easily controlled direct seeding is extensively used with excellent results. The availability of water is essential because relatively deep water discourages the growth of grassy weeds. Effective water control ensures that the plots can be drained during the seedling establishment phase.

Two methods of direct seeding are most commons broadcasting directly onto soil that has been prepared thoroughly by plowing and several harrowings, or broadcasting onto standing water (usually from airplanes). Ungerminated or pregerminated seed may be used. The main advantage of improved direct seeding is the low labor cost. The several operations of nursing -preparling seedbeds, watering, uprooting, and transporting of seedlings - are completely eliminated. In areas in which labor costs are high, direct seeding can cut production costs significantly. Nevertheless there are various disadvantages:

- exposure to rats and birds
- weed control is difficult without the use of herbicides

II. Transplanting

a) Hand Transplanting

Hand transplanting is the most widely practiced method of stand establishment in small-scale, labor-intensive (wet) farming systems throughout the world. Seedlings are nursed in seedbeds and then uprooted for transplanting into lowland puddled soil.

The major advantage of transplanting is that the seedlings gain a significant head start over weeds. However, transplanted seedlings tend to grow more slowly than direct-seeded plants because of the root damage suffered during uprooting. Furthermore, hand transplanting is extremely labor-intensive.

Hand transplanting is done either randomly or in rows. Random transplanting, traditional in some parts of Africa and most of Asia, is significantly faster, but the distance between seedlings is not uniform, and no definite aligning pattern is followed. Consequently, randomly-transplanted stands are often uneven, difficult to weed (the use of mechanical row weeders can be ruled out), and difficult to walk around in (e.g. for purposes of broadcasting fertilizer). Straight row transplanting is done wit.. the use of planting guides (usually a rope knotted at regular intervals, or a planting stick) Straight row planting is time-consuming, but it offers several advantages: optimum spacing is possible, the row weeder can be used, and the stand of plants is easy to walk around in during fertilizer and/or pesticide application.

Transplanted seedlings should not be planted too deep (1/2" -1" is best), since tillering is discouraged when the lowermost internodes become completely buried. Never thrust seedlings deep into the soil in order to make them stand upright. For best results, barely cover the roots - the seedlings will right themselves within a day or two, and in the long run they will tiller more vigorously and yield better.

Plant spacing is an important factor and will vary depending on variety, soil fertility, and season of planting. Generally, rice plants are spaced more widely in the wet than in the dry season because in the wet season they tend to grow more profuse leaves and tillers, thus increasing mutual shading. As a general rule, encourage the farmer to plant 3-4 seedlings/hill (except with very low-tillering varieties, which should be planted at a rate of 5-6 seedlings/hill). Space the hills 8"X8" during the wet season, 6"X6" during the dry season. But be prepared to modify these general recommendations to fit Particular situations.

Notes It is sometimes difficult to decide whether or not to advise a farmer to plant in rows. In theory row planting is preferable to random planting, but in certain situations the extra time required will not always yield better results (e.g. if the farmer does not own a row weeder and will not be walking around in the rice to fertilize). Generally farmers will be reluctant to spend the extra time to plant in rows, and the extension agent must be careful not to alienate them by a rigid insistence that things be done "by the book." Often the best approach is to experiments offer to help plant a few plots in rows, and then let the individual farmers decide whether or not the additional labor investment pays off in terms of a more uniform, easily-weeded, and higher-yielding stand of plants.

b) Broadlings

Broadling is a method of stand establishment practiced in parts of Asia where rice paddies are extremely boggy, making it difficult to walk in them. Nursed seedlings are thrown randomly into the puddled soil from the edges of the paddies. Much practice is required before uniform stands can be achieved on a consistent basis. The seedlings establish themselves quickly, since the roots do not get buried deep in the soil. Although broadling can be effective in some very specialized farming eco-systems, the technique requires smaller plots than are found ordinarily.

Rice Production: Chapter 5 - Methods of raising seedlings

Introduction

Rice which is to be transplanted into lowland puddled soil must first be nursed on seedbeds. The main reason for nursing rice is simple: to give the seedlings a substantial head start on weeds. Three types of nurseries are used in Sierra Leone - the wet bed nursery, the dry bed nursery, and the dapog. Each type has advantages and disadvantages, and you will probably end up using different nursing methods depending on the situation. Always keep in mind that it is really very easy to raise healthy seedlings if you are prepared to take enough time to do the job properly. Success in raising healthy rice seedlings depends mainly on constant supervision of the seedbeds and proper management.

I. The Wet Bed Nursery

Raised seedbed preparation

The wet bed method of raising rice seedlings is the most popular worldwide, Although wet bed nursing is not traditional in Sierra Leone, extension agents have been able to introduce the use of wet bed nurseries with fair success.

The nursing of rice seedlings by the wet bed method is carried out on raised beds within the swamp. Select a fertile, level plot with good water control. Soil preparation, should always be very thorough. At least one plowing and a careful puddling are necessary to loosen the soil, as well as to facilitate the decomposition of organic matter. The addition of organic material to plots designated as nursery areas can help ensure seedling vitality, provided it is added early enough to decompose completely.

After soil preparation is completed, peg out the nursery bed, with bush poles and string. The beds should be approximately one meter (1m) wide. The relatively narrow width ensures that any area within the bed can easily be reached from either side. Leave alleyways of approximately 40 cm between the beds for use later as irrigation, channels. Scoop soil from the alleyways by hoe or by hand to construct the beds, which eventually should be raised 10 cm above the original surface of the plot. Work thorough the raised soil wit}-, your fingers, breaking up clumps and removing sticks, roots, and stones (this will facilitate uprooting of the seedlings later on). Finally, smooth the surface of the bed, using a board or your flattened hard.

Wet seedbed

Broadcast pre-germinated seed on the beds, being sure to achieve an even distribution. It i very important not to space the seeds too close, as they will crowd each other out when they begin to grow. An application rate of five (5) pounds /10m bed gives excellent results. When the seeds have been sown, smooth over them with your hands to cover with a thin layer of soil. This will help protect them against heavy rain or birds. In some cases it will also be necessary to cover the newly-sown beds with pal.´, frond.>, banana leaves, grass, or brush.

It is extremely important to keep the beds moist at all tines. Although water is usually not a problem with the wet bed, make sure the farmer checks the nursery at least twice a day If it is not raining every day, moisten the beds morning arid evening by splashing water up from the irrigation channels between the beds.

Seedlings in the wet bed nursery can be attacked by insects, although pest infestation is generally not a big problem (if it is, encourage the farmer to make subsequent beds toward the centers of the swamp, away from the brushy peripheries where insects breed). If it becomes necessary to resort to the 'se of a chemical pesticide, do not spray until the seedlings are at least five days old.

Sowing of seeds

The seedlings should be ready for transplanting from 14 days onwards, depending on the variety and the conditions. Younger seedlings are always preferable, as they establish themselves more quickly. The "fourth leaf" stage is generally regarded as optimal. Remember to flood the beds completely beforehand (submerge the soil, not the rice) to minimize damage to the seedlings. Uproot seedlings by holding a few at a time between thumb and forefinger at the base of the culm and pulling sideways. Always handle seedlings with extreme care. Seedlings which are handled gently during uprooting and transporting recover much more quickly when transplanted than those which are crushed, bruised, or allowed to dry out.

Advantages of the wet bed nursery:

- situated right in the swamp

- irrigation water readily available

- seedlings grow rapidly seedlings easy to uproot

- minimal disease and pest problems

- excellent for dry season crops

II. The Dry Bed Nursery

Dry seedbed 

Most traditional swamp farmers in Sierra Leone use a form of dry bed nursery. However, almost invariably the beds are constructed hastily, without proper tillage of the soil, and the resulting seedlings tend to be of poor quality. Don't be misled into thinking that dry bed nurseries cannot produce healthy seedlings; under proper management, dry bed nurseries can produce excellent seedlings.

Select a level or gently sloping area near a convenient water source. The hillsides immediately adjacent to a swamp generally make excellent locations for dry bed nurseries. Flow and harrow the soil twice to obtain a fine till. At least 10-15 cm of topsoil must be opened up and well pulverized. Addition of decomposed organic matter and/or partially burned rice straw or rice husks will help in keeping the soil aerated and will make it easier to uproot the seedlings.

Peg out the beds in the same manner as wet beds. Scoop soil from the alleyways, using a hoe or shovel. Level the beds and crush any remaining clods by hand or with a stick.

Broadcast the pre-germinated seed just as you would on a wet bed. The application rate should be similar -five (5) pounds/10m bed is good. Be careful to cover the seeds completely with a thin layer of soil. If heavy rains or birds threaten, cover the beds with fronds or leaves.

The beds should be watered thoroughly immediately after planting and twice every day thereafter. Soak the bed - well ( to near saturation). If irrigation water is available, water can be sent along the channels and splashed onto the beds otherwise, water must be carried in by hand It is impossible to overemphasize the importance of constantly watering dry bed nurseries. Seedlings growing, on wet beds can usually absorb sufficient water from below the surface, but dry bed seedlings are totally dependent on rain and hand waterrig. If the beds dry out for even one day, the growth of the seedling may be seriously impaired. Do not encourage a farmer to construct dry bed nurseries unless he can be depended on to water them regularly.

Dry bed seedlings will not grow as fast as wet bed seedlings. Seedlings on the dry bed should be ready for transplanting from 21 days onwards. Water the bed to saturation before uprooting:, to make sure the soil is moist and loose.

Advantages of the dry bed nursery:

- seedlings develop excellent root

- seedlings easy to uproot

- beds can be made near the farmer's house

III. The Dapog Nursery

The Dapog Nursery

The dapog method of raising seedling originated in the Philippines and is now, fairly common in South and Southeast

The dapong nursery is constructed for the raising of seedlings without any soil whatsoever. Rice seeds contain sufficient food in the endosperm to permit the young seedling seedlings to grow for up to 14 days without receving any outside nutrients except air, water, and sunlight. Consequently, it is possible to nurse seedlings without actually sowing them in soil.

The dapong nursery can be located anywhere convenient, as long as it is near a reliable water supply. It is usually a good ideal to locate dapong nurseries where they earl be watched at all times, since they require constant watering and very susceptible to bird (including chicken) attack. Construct a raised earthern bed roughly one meter square - the exact shape isn' too important - and cover it with green bahana leaves, or better yet plastic sheeting. Keep the surface of the bed as level as possible, but construct a low raised border to hold the seeds in place after they have been sown and to prevent water from escaping.

Soak and pre-germinate the seed as with the other types of nursery Pre-germinate a little more seed than usual, because dapog seedlings are quite small when transplanted and difficult to separate; almost inevitably, the farmer will need more of them. Spread the seed in a solid, even layer on the dapog to a depth of approximately 2 cm (5-6 seeds thick). Gently sprinkle water over the seeds, taking care not to dislodge them. As the seeds expand during the next few days, press them firmly in place with a board to keep them compacted

Keep the seeds moist at all times! Without the insulation of a layer of soil, they will dry out very quickly if they are not watered constantly. From about the third day, keep the bed continuously flooded with a thin layer of water.

Regardless of the duration of the variety, dapog-raised seedlings will be ready for transplanting after 9-14 days -by then the food material contained in the endosperm will have been exhausted, and the seedlings will quickly begin to die off. On the day of transplanting, simply roll up the entire seedling mass (the roots will have matted together to form a soft of rug), throw it over your shoulder, and head for the swamp.

Advantages of the dapog nursery:

- fastest method of raising seedlings

- small nursing area

- situated near farmer's house

- excellent for replacing small quantities of seedlings destroyed by pests

- dapog seedlings recover fast from transplanting because they are not uprooted

Big money in "speciality rices"

While much research has been done on common, high-yielding rice varieties, far less attention has been paid to special kinds, even though they command higher prices...

Aromatic, coloured, glutinous, organic, 'boutique", - 

why should rice always be bland and white?

First question: What makes Basmati rice smell so good? Science has the answer - Basmati grains contain 0.09 parts per million of the chemical compound 2-acetyl-1-pyrroline, which is about 12 times more than concentrations found in unscented rice varieties and enough to give Basmati its distinctive spicy fragrance. That aroma - along with fine, slender grains and a soft, fluffy texture when cooked - has made Basmati the world's most sought-after rice, fetching up to 10 times more than common rices on international markets.

Second question: Why don't more of the world's rice farmers switch to growing varieties like Basmati and a host of other high-value "speciality rices" which today account for less than 10% of global rice production? "That's because until recently, rice was viewed mainly as a basic, staple food," explains Dat Van Tran, executive secretary of the International Rice Commission (IRC) based at FAO in Rome. "So, while much has been researched and written about the more common, high-yielding rice varieties, far less attention has been paid to special kinds, even though they command higher prices. To exploit new market opportunities, farmers need sources of up-to-date information on breeding, production and marketing of speciality rices."

To meet that need, the IRC and AG's Crop and Grassland Service have produced a new publication, Speciality rices of the world, which will be presented at the next session of the Commission in Bangkok this month (Details). With contributions from 60 experts in Asia, Africa and the United States, the book reviews in detail the latest breeding strategies, agronomic practices, production packages and market trends for several dozen aromatic, coloured, glutinous, organic and "boutique" rice types.

Aromatic rice: Asia's aromatic rices - including Basmati from India and Pakistan, Thailand's Jasmine rice, and hundreds of little-known locally adapted varieties - appear to hold great promise. Export markets in Europe and North America are expanding rapidly and local demand is also strong. In fact, says Dat Van Tran, "it is estimated that demand for this rice type cannot be met at any given time". The persistent undersupply of aromatic rices is explained by the relatively limited area planted to the crops, and by their low yields. In China, for example, the planting area of aromatic rice (used mainly in foods and cakes) is less than 1% of the national rice acreage and, due to lower grain fertility and susceptibility to rice blast, yields are 10% lower than those of common rice. In India, traditional Basmati varieties are unresponsive to fertilizer and difficult to harvest, and yield around two tonnes per hectare, well below the 5-6 tonnes per ha produced by high-yielding varieties. Despite decades of research, India's rice agronomists have yet to produce a high-yielding Basmati that growers and millers are ready to adopt. In neighbouring Pakistan, in contrast, improved varieties are widely grown, but the level of aroma in their grain does not match that found in the traditional cultivar.

"There is a general need to improve the yield potential of aromatic varieties", comments Dat Van Tran. In Thailand, a research programme is combining a Jasmine variety with the higher-yielding semi-dwarf plant type, which is photoperiod-insensitive and less vulnerable to diseases and pests. Drawing on the great genetic diversity among local aromatic rices, a breeding programme co-sponsored by FAO in India is developing Basmati hybrids, while the International Rice Research Institute in the Philippines expects improved Basmati varieties with high-yield potential to become available within the next two to three years.

Rice, briefly... Rice (genus Oryza) is tolerant to desert, hot, humid, flooded, dry and cool conditions, and grows in saline, alkaline and acidic soils. Of 20 Oryzaspecies, two are cultivated:Oryza sativa, which originated in the humid tropics of Asia, and O. glaberrima, from west Africa. Asian cultivated rice has evolved into three eco-geographic races (indica, japonica and javanica).Indica varieties account for 80% of cultivated rice, and feed about 3,000 million people, mainly in developing countries. Indica and japonica have great variabilities for grain shape, size, colour and chemical composition. For example, different quantities of amylose and amylopectin affect cooking quality and possible uses.

Coloured rice: Some speciality rices are prized not for aroma, but their colour, which is determined by levels of anthocyanin pigment in different layers of the pericarp, seed coat and outer grain layer. The endosperm colour of rice ranges from white and various shades of translucent to red, purple and black. In China, non-milled black rice is used as natural colorant in cakes, dumplings, porridge, New Year cakes and black wine. It is also considered highly nutritious, rich in B vitamins and many trace elements (e.g. bronze, manganese and calcium). The purplish-black Jieguno variety is said to strengthen the immune system and hasten the healing of bone fractures. Although China has released some 54 modern black varieties with high yield, good quality and multiple resistance, less than 1.3% of the country's ricelands are under the crop. Researchers say that red rice, most of which is processed into white milled rice for normal cooking and eating, has stronger tolerance to unfavourable environments, such as infertile lands and mountain areas.

Glutinous ("sticky") rice: The consistency of "sticky" rice is determined by two kinds of starch in the kernels, amylose and amylopectin. The more amylopectin, the stickier the texture. Glutinous rice is easily distinguished from other varieties by its milky colour. Most widely consumed where it is grown - mainly in dry areas of northern Thailand, Laos and Cambodia - it is often used as an ingredient in sweet dishes and snacks, and for brewing beer. Per capita, Laos is the largest producer and consumer of glutinous rice, which accounts for about 85% of its rice production. As for many other speciality rices, "sticky" varieties bear much lower yields - in Thailand, average yields of non-glutinous varieties are around four tonnes per ha, compared to 1.9 tonnes per ha for glutinous types. But, Dat Van Tran observes, lower yield is compensated for by higher prices, and demand is increasing, especially on export markets.

Boutique and organic rice: Combining glutinous and aromatic characters are the so-called "boutique" rices, which include many traditional Lao varieties and others grown and consumed in Thailand and Cambodia. "Boutique" rices are considered to have the greatest potential for export markets, and breeding programmes have focused on boosting their yield. In China, for example, scientists have developed from a local aromatic cultivar ajaponica waxy-aromatic variety, Shangnongxiangnuo, which yields an impressive 7.5 tonnes per hectare. Meanwhile, many rice growers are switching to production of organic rice - while exact statistics are unavailable, surveys show that both developed and developing countries (mainly in Asia) are growing rice organically, hoping to enter the world's $10,000 million commerce in organic foods. "Growth in this rice type is slower," says Dat Van Tran, "due to higher costs, unavailability of inputs and technology, and limited participation of supermarkets and retail outlets."

In conclusion, Speciality rices of the world sees a rosy future for the sector: "With growing prosperity, consumers are looking for better quality rice. Countries that could feed themselves with marginal quality but high yielding indica or hybrids, such as Republic of Korea, have switched almost entirely to low-yielding but superior qualityjaponica. Similarly, in India and Pakistan, demand for high quality Basmati has risen dramatically. Asians who migrate to Middle East, European and American countries can afford the best quality Basmati or Jasmine rice at any price. Thus, the future of speciality rices is linked to the growing prosperity of people."

Published July 2002, Food and Agriculture Organization of the United Nations