Low-external Input Rice Production - Chapter 4 - Water Management / Cropping Patterns

Water management for rice in drought-prone locations

A number of strategies exist for farmers to minimize risks and reduce losses in drought-prone and rain fed rice-producing areas. These strategies focus mainly on the following: varietal selection, timing of planting to minimize drought damage, maintenance of water level, cultural practices aimed at conserving water or improving drought resistance and altering the physical farm environment.

1. Varietal selection

· Select drought-tolerant varieties if drought is likely to occur. In general, IRRI found droughttolerant rice varieties to have long, dense and thick roots. Traditional varieties like BE-3, Peta and Intan tolerate some drought but yields are lower than modern varieties. The IRRI varieties IR6, IR46 and IR64 also withstand mild drought although IR36 and IR64 are prone to tungro disease.

· Plant very short-duration varieties to avoid the drought period entirely.

2. Timing of-planting

· Plant the rice such that the vulnerable reproductive stage does not fall during the drought season. This presupposes a regularly occurring drought in a region which the farmers anticipate and plan around.

· Synchronize planting with neighboring farmers to minimize irrigation water wastage.

Timing of-planting 

3. Maintenance of water level

· It is important to provide the crop enough water to induce maximum tillering (formation of stalks) for a good cover (canopy) so that water losses by evaporation would be minimized.

· Water is essential during flowering on from 55-70 days after transplanting of the shortduration varieties. If simultaneous planting is done, 800-1,000 mm of water would be minimum requirement.

· Fields need only be kept moist (not flooded) all the time with a 1-2 mm layer as minimum. Using this strategy gives a 30-50% cut requirements without yield losses.

4. Other cultural practices

· Maintain rice paddy dikes to minimize seepage and clean irrigation ditches regularly.

· Establish good weed control. Most weeds are much more efficient than rice in exploiting soil moisture.

· Supply nitrogen (N) and other fertilizers early. If using less than 30 kg N/ha, apply all of it basally. If applying more than 30 kg N/ha, use the best split (2/3 basal and 1/3 topdress 5-7. days after panicle initiation [DAP]). This improves the plant's drought resistance by encouraging faster root growth and, thus, more soil area can be exploited for soil moisture.

· Increase soil organic maker (OM) content. OM improves the soil's water absorption and retention capacity.

· Minimum tillage (one plowing and one harrowing) reduces the water requirement for land preparation and speeds crop establishment, lowering the risks of an end-of-season drought. Minimum tillage is possible in fields where perennial weeds are few.

· Direct seedling of pregerminated seed can be used where there is not enough water to thoroughly prepare the land for transplanting. Direct seeding also results in a stronger root system. This gives the crop batter capacity to survive during short drought.

· Farmers should use the early rains of May for land preparation since this water largely goes to waste.

5. Altering the physical farm environment

· If feasible, impound water in one-fifth of the land area. A 200 sq.m structure will be enough to supply the water for a half hectare of rice crop and could also be used for fish production.

· Reduce the area planted to rice to increase the amount of irrigation or residual rainfall water available. The Sorjan system developed by farmers in Indonesia is one such method of water management. Tests done in Indonesia show that this system nearly doubled the amount of available water for rice production. Devote low-lying areas of the farm to rice and plant the upper areas with dryland crops. The rice crop can take advantage of the higher water table in the lower areas and can utilize runoff from the upper areas. (See the technology sheet on Sorjan: Towards Rice-based Integrated Cropping System.)

· Plant windbreaks to reduce evapotranspiration of the rice crop.

· At the national level, deforestation is the main cause of irrigated water shortages for rice production. For long-term sustainability, the nation's mountainous area must be reforested.

Legume crop rotation with rice

INTRODUCTION:

In rainfed lowland areas which are traditionally planted to only one crop of rice per year, land use can be optimized by using the pre- and/or post-rice wet period to grow-legume crops. Legumes are suitable rotational crops with rice because they:

· can mature in 55-90 days.

· can be grown as pre-rice crop when rainfall accumulation reaches 100 mm/mo or as postrice crop using the receding rain and residual soil moisture.

· are acceptable crops because they are easy to prepare for consumption or to sell at the market.

· are drought-tolerant.

· are capable of using atmospheric nitrogen and contribute nitrogen to the soil. 

IMPORTANCE:

1. Intensifies land use and increases crop production per area per year.

2. Provides an additional source of food and income to farmers. Legumes can also provide biomass for green manure and fodder.

3. Sustains soil productivity through nitrogen cycling with legumes.

4. Weed production is reduced by planting an otherwise fallow area. 

DESIGNING THE CROP ROTATION PATTERN: (Refer to the figure on theoretical rainfall occurrence and proposed legume-rice sequences)

1. Based on knowledge from past years or from rainfall data, determine the onset and the end of the rainy season.

2. Choose short-maturing varieties of both rice and legume crop to accomodate a three-crop sequence or to avoid water stress.

3. Estimate the planting and harvesting dates of each crop in the cropping sequence.

4. If, based on the rainfall occurrence and drainage system, only a two-crop sequence is possible, there is a flexibility to choose a longer duration crop variety which has other desired characteristics.

Theoretical rainfall occurrence and the proposed legume-rice sequence

ADDITIONAL POINTERS:

1. The field should be well-drained. This minimizes flood damage if heavy rains occur during the legume cropping season and it facilitates post-rice land preparation for legumes.

2. If no legume crop will be grown after the rice crop, the field should still be plowed after rice harvest so that land preparation for the following pre-rice legume could be done quickly and easily using the early rains.

3. For the post-rice legume, a variety high in both grain and biomass yield (usually indeterminate or late-maturing) such as indeterminate cowpea, Indigofera, etc., is desirable so that more residues will be produced for use as fodder during summer or as green manure for the next crop. The crop should be tolerant to drought.

4. Other criteria in choosing crop varieties/species to be used are: adaptability to the site; marketability; tolerance to crop hazards -- like excess moisture (for pre-rice crop), drought (for post-rice crop), wind and short-term floods.

The ideal legume species are mung bean and cowpea. They are planted with 50 cm row spacing at a population of 300-350 and 350-400 thousand plants/ha as pre-rice and post-rice crop, respectively.

5. If the available time for pre-rice legume is less than 60 days, green manures, such as Sesbania, could be planted instead of grain legumes.

Rice ratooning

Ratooning, the ability of rice plants to regenerate new tillers after harvest, may be one practical way to increase rice production per unit area and per unit time. Because ratooned rice has shorter duration than a new crop, it may increase productivity in areas where cropping intensity is limited by inadequate irrigation facilities or by a second crop where the rice season is less than 180 days. Besides short duration, it costs less to grow a ratoon crop than a new crop. The major advantages of rice ratooning are:

· Lower production costs because of savings in land preparation and plant care during early growth;

· Short duration;

· Efficient use of the growing seasons, especially in monsoonal climates;

· Higher yield per unit area in less time;

· Possible maintenance of the genetic purity of a variety or hybrid rice through several seasons;

· Low irrigation water requirements;

· 60% reduction in the amount of water needed to compare to a second crop of transplanted rice; and

· 50-60% reduction in the amount of labor needed especially important considering the shortage of labor when the first rice crop is harvested and the second is planted. 

Yields are generally lower in a ratoon crop than in a transplanted second crop. However, the capital and labor savings are often enough to make a ratoon crop more profitable. The lower yield potential outputs of 3-4 T/ha have been frequently reported.

HOW TO HAVE RATOON CROP PRODUCTION:

Selecting the right variety is one of the most important and critical steps in obtaining high crop yields from ratoons. An ideal cultivar for rice ratoon cropping should have the following traits:

· Produces ratoon tillers after and not before harvest;

· Tillering from basal, not upper, nodes;

· Sixteen ratoon tillers/hill at 20 x 20 cm spacing;

· At least 3 leaves/tiller;

· Resistance to major disease and insects;

· Synchronized flowering and maturity;

· More than 60 growth duration from cutting to maturity; and

· High grain yield. 

Recommended land preparation practices for the main rice crop are undertaken only once because the ratoon crop does not require another round of land preparation. Deep plowing (25 cm depth) increases yield of the ratoon crop but under Philippine conditions, this is not practical.

Crop establishment in the main crop may either be by transplanting or direct seeding. Planting density is a more important factor in determining yield: the more plant/sq.m. the higher the yield (if no lodging occurs). Direct seeding usually results in a higher plant density than does transplanting at 20 cm x 20 cm distances but if the triple row transplanting method is used, plant density is about the same and less lodging occurs.

Fertilization of the main crop is essential for good yields in the ratoon crop. Deep placement of N fertilizer, if feasible, should be practiced as yields in the ratoon crop are increased by this practice. Green manuring practices and Nitrogen rates recommended for the first crop should be followed. N should be applied immediately at the harvest of the main crop to stimulate tillering of the ratoon crop. Suggested rate is 15-45 kg. N/ha.

Ratooning is a viable option for those farms where a second rice crop is not profitable and upland crops are either not profitable or cannot be grown due to poor drainage or other. factors.

Sorjan: towards rice-based integrated cropping systems

Sorjan, an indigenous technology of Indonesia, is a series of sinks or canals alternating with raised beds. Rice is usually planted in the sinks and a wide variety of upland crops is grown in the raised beds. The use of Sorjan (on 1000 sq.m) as one component of an integrated rice farming system results in higher and more regular income for the farmer due to the following:

1. Increased production per unit of land area 

2. Crop Diversification 

· Growing of high-value, off-season crops

· Simultaneous growing of a wide variety of lowland and upland crops assures farmers a good harvest from at least one of the crops.

· Increased fodder production for livestock. 

3. Earlier rice crops and higher yields in partially irrigated or rainfed areas

4. Other Benefits 

· Increase in quantity and variety of food available for home consumption

· Increased fertility of sinks

· More even use of labor throughout the year

· Practical and ideal for farmers whose land area is less than 1 hectare

· Could be adopted in a wide range of agro-ecological conditions. 

Note: This technology has a high labor requirement during the initial development of the plots.

1. INCREASED PRODUCTION AND LAND UTILIZATION

Production increases in Sorjan because water is used more efficiently, weed control is easier and both upland and lowland crops are grown in environments more closely tailored to their needs.

Water collects and stays in the sinks -- where it is needed most. The standing water aids rice growth and keeps weed populations to a minimum. The upland crops have a stable water supply (the standing water in the sinks which is available to them through wicking action), combined with good drainage and air circulation.

Along the sink portion (as well as in lateral canals) fish could also be introduced while, at the top portion of the sink, trellises for vegetable production are also recommended.

Under these Ideal conditions, production is very high. In work done by a Masteral student at U.P. Los Ba yields of grains and fodder from the Sorjan were 21 T/ha/yr of grains and 14 T/ha/yr of fodder for continuous cropping of rice.

2. DIVERSIFIED PRODUCTION

The growing of upland and lowland crops at the same time in the same field practically assures the farmer a good harvest of at least one of the crops. High-value crops, such as tomatoes and onions, fetch very high price when grown in the rainy season -- which is possible in Sorjan. The most profitable cropping pattern tested by IRRI was tomatoes -- onions -- bush sitao with a net income of more then P40,000/ha.

The quantity and quality of fodder production are also greatly increased. The addition of grain legumes, such as mung bean, provides high protein fodder for livestock. Intensive production of fodder grasses and trees to supplement livestock feeds is possible in this system. Napier planted in the side of the beds prevents the erosion of the beds (reducing maintenance) and produces more than 2 kg of high quality fodder grass/linear meter every month. In the UPLB study, fodder produced was enough to meet the feed needs of 11 carabao heifers or 29. cattle fatteners.

In the study conducted by IIRR in 1988 (dry season), data showed that the net income of rice planted on the sink portion yielded P9,471 on a hectarage basis, while on the elevated plot, cowpea had P10,773 and napier grass with P2,706.

Rice-fish also has very good potential in Sorjan due to the greater degree of water control. IRRI has recorded yields of nearly 200 kg of fish/ha/crop in addition to rice and upland crop yields. Yields could be tripled according to data from India.

3. EARLIER RICE CROPS WITH HIGHER YIELDS

In rainfed or partially irrigated areas, farmers must wait for enough water to accumulate before plowing and puddling the soil (land preparation). In Sorjan sinks where the rice is grown, water accumulation is faster because of runoff from the beds. Tests in India indicate that 46% of the rain falling on the beds is collected in the sinks. Fields can be puddled up to three weeks sooner. The same trials in India compared rice yields from Sorjan and normal rainfed rice over three years. Yields were 70% higher per unit area in Sorjan. This means that even by taking half the land out of rice production (i.e., the raised beds), yields were almost the same (1.5 T/ha for rainfed rice production and 1.3 T/ha in Sorjan).

BED CONSTRUCTION:

The construction of the beds can be done in several ways: plowing with an upland plow and shovelling the soil to form the beds; or plowing a flooded field, harrowing to move the soil into a rough bed and then shovelling to straighten the edges.

The method chosen will depend greatly on labor availability. An area of about 1,000 sq.m. requires anywhere from 300-600 man hours -- which can vary upon the number of beds to be constructed, their width and height.

DETERMINING BED HEIGHT AND WIDTH:

A number of factors need to be taken into consideration when deciding on bed height and width:

Height:

- Terrain. If field is sloping, a lower height is needed because there is less problem with drainage (for the upland crop planted on the beds).

- Chance of flooding/height of floodwater. If flooding occurs, the bed must be high enough so that the upland crops will not be flooded. 

- Rate of soil erosion from bed to sinks. Original heights of bed should be higher under high erosity conditions. 

- Soil fertility/depth of topsoil. Sinks should not be dug so deep that subsoil is exposed.

Width (and/or number of beds): 

- Water needs. If the land is rainfed, the width will be determined by how much runoff from the beds is needed for the rice in the sinks. 

- Convenience of the farmer. If the farmer plans to plow the beds, these need to be wide enough to facilitate the plowing operation. On the other hand, making many narrower beds is faster than making fewer but wider beds. 

INCREASING FERTILITY OF SINKS:

Removing topsoil from the sink area reduces soil fertility which will affect lowland crop yields. The farmer should therefore focus efforts on increasing soil fertility with large amounts of organic matter. Some possibilities include:

· planting green manure or grain legume in the sinks as soon as possible after formation

· mulching the crops with straw during the dry season

· moving livestock housing to sink areas during the dry season fallow period

· using Azolla if feasible (might be possible even in rainfed areas due to increased moisture availability and better water control). 

If moisture is present in the raised beds plant soybean, cowpea, or mung bean. Mung bean, in particular, does very well in newly constructed beds. Mulch the crop as well. Some upland crops are better suited than others to new Sorjan beds including sweet pepper, cucurbits (cucumber, squash and ampalaya) and grain and vegetable legumes.

SOURCE: PCARRD Monitor

A. for waterlogged areas

B. for predominantly rice-based areas

Maximizing the dry season for post-rice alternatives

RATIONALE:

There is a need to maximize the use of residual moisture an/or land area in rice-based farming systems, through crop-intensification by raising alternative crops after rice. This also contributes to the diversification of the farm.

Diversification of crops in a rice-based system, particularly with the use of vegetable crops, improves overall farm income, reduces the degree of deterioration of fertility, increases the uses of residual moisture and cropping intensity and improves daily cash flows. Such multiple cropping systems also help reduce insect populations.

CONSIDERATIONS:

· Is land efficiently used?

· Are all land areas utilized?

· Does the present use conserve the land?

· Is available water efficiently used?

· Are the crops grown when they are best suited?

· Is farm work designed to employ/utilize the labor of other family members?

· What capital resources are available?

Figure

IN THE SELECTION OF CROPS, CONSIDER THE FOLLOWING:

· market potential/demand
· price
· family benefit
· knowledge/skill in growing
· maturity of varieties
· time of planting
· method of planting

TRADITIONAL SYSTEMS:

1. Immediately before harvesting, mung bean seeds are broadcasted into the rice paddies. During harvesting, the mung beans are trampled thus establishing a mung bean crop stand.

Mung bean seeds are broadcasted

2. The rice stubble is cut to the ground and used as a mulch (in addition-to the rice straw from threshing). After mulching the field, the area is flooded for about 1/2 day or until it is saturated. The area is then planted with onion or garlic. (Nueva Ecija)

The rice stubble is cut to the ground

3. The field is plowed and harrowed and planted with various vegetables. (Nueva Ecija)

The field is plowed and harrowed

4. The paddies are cleaned of rice stubble, flooded until saturated and holes are dug at a 2 m x 2 m distance. Watermelon and musk melon are then planted. (Nueva Ecija and Cavite)

The paddies are cleaned of rice stubble

CROPPING PATTERN FOR A RAINFED LOWLAND RICE-BASED AREA: 

Rice is grown from July to October when water is available and the supply is adequate. Then, using residual soil moisture and available rain water, vegetable production can be feasible during the dry season.

CROPPING PATTERN FOR AN IRRIGATED LOWLAND RICE-BASED AREA:

Two crops of rice can be grown between May and January. The first with rain and the second with supplemental irrigation. Vegetable crops can then be grown during the dry months using available residual soil moisture.

Watermelons in rice paddies

RATIONALE:

Scarce land resources can be optimized and farm income can be increased by planting high value crops in rice paddies during the months following the rice harvest. Farmers in Cavite, Philippines, have demonstrated that planting watermelons can be a profitable venture if the activity is properly timed. Demand for watermelon is high, especially during the hot, summer months when it is a popular fruit used as dessert. The practice can also help farmers to recover any losses they might have suffered in their rice crop resulting from unforeseen circumstances like typhoons, pests and diseases, fluctuations in price and other causes. Labor inputs for crop establishment are low because minimum tillage is used, thus requiring little land preparation.

CONSIDERATIONS:

· Recommended Varieties

Cultivar	Maturity	Seed Rate/ha.
Sugar Baby	65 days	3-4 kgs.
La Mallorca	80 days	-do-

· Cropping Pattern

In order to receive the best price, watermelons should be planted from September to late October. Therefore, they should be planted 14-25 days before the rice crop is harvested. Planting during this period enables the farmer to harvest the crop earlier than most farmers, thus he can command a higher price for his produce. Also, raising watermelons during the cooler climate helps avoid possible thrips infestation which usually occurs during the hot, drier months of the year. Once the watermelons are harvested, batao (Dolichos lablab) can be sown as a cover crop and green manure for the remainder of the dry season.

Cropping Pattern 

· Land Preparation -- Direct seeding is a common practice in planting watermelons. 

a. Identify the rows where the watermelons will be planted.

b. Using a stick or planting board, push the rice plants to one side -- creating a space in which the planting can be done.

c. Dig the hole 20-25 cm deep and 20-25 cm wide. Place the topsoil one side of the hole and the subsoil on the other side. The holes are spaced 1.25 m between rows and 1 m between hills.

Push the rice plants to one side

The holes are spaced

· Planting

Mix equal amounts of compost or decomposed manure with the topsoil set aside earlier. Return the mixture to the hole. Sow 4-5 seeds. After the rice is harvested, thin out the unhealthy plants, leaving only three to mature. Place mulch around the base of the plant.

Place mulch around the base of the plant