Switching over to Direct Seeding of Rice (DSR) technology

THE methods of stand establishment can be broadly divided into direct sowing of pre- or un-germinated seeds and transplanting of seedlings. Traditionally, nursery seedlings are raised which are then transplanted in standing water. This traditional transplanting system not only helps in controlling the weeds but also ensures a premium quality paddy. But the looming water crisis and increasing labor cost are inducing farm experts to find out alternate ways of seedling establishment. Direct sowing of germinated or un-germinated seeds is one of the alternatives. The most suitable planting technique depends on locality, soil type, and crop ecosystem. Crops can be direct seeded or transplanted. Similarly, transplanted crops can be established manually or by machine. Direct seeded crops tend to mature faster than the transplanted crops but have more competition from weeds.

Direct seeding method is becoming more popular among rice farmer as it is economical than transplanting. The yields are also comparable with transplanted rice if crop is properly managed. Direct seeding methods could be divided into wet seedling and dry seeding. Wet seeding: In wet seeding pre-germinated seeds are broadcasted into puddled and leveled field which are free from standing water. At the time of puddling basal fertilizer mixture should be added. After germination of seed, seedling desiccation due to water stress should be avoided by intermittent wetting of the field. When seedlings are of about 5cm tall (about a week after sowing) water is impounded to prevent germination of weeds and desiccation of seedlings. The stand establishment by this method varies with the quality of land preparation, weed competition, water management and rainfall during the initial period after sowing.

Row seeding of germinated seeds could also be done but it is practiced on a limited scale because of the cost and the difficulty in obtaining implements. This method of sowing will help in controlling weeds, especially mechanical control and management of the crop.

This system also helps in maintaining optimum density of seedlings, whereas random broadcasting often leads to low or high seedling density. Selection of a suitable variety for direct seeding is important as there is a genotypic variability in germination under submerged conditions.

However, if field can be maintained at or below field capacity for about five days, focus should be on varieties which process good initial seedling vigor. Seedling vigor is mainly determined by the seed quality and other cultural practices. Stand establishment is often poor with direct seeding because of poor quality seed paddy, poor land preparation, weed competition, poor water management, unfavorable environmental conditions and physical damages.

Due to declining water resources and high water requirements of traditional puddled rice transplanting in wheat–rice cropping system, various technologies were discussed. Direct Seeding of Rice (DSR) is one of the best sowing technique in rice that has scope and potential to address most of the problems faced by the farmers in wheat rice. Area under DSR has already increased to 26 per cent of the total rice area in the world like South –East Asia. Direct Seeded Rice (DSR) in place of the traditional transplanted rice is a way to reduce labor charges for nursery raising, puddling and transplanting. DSR is sown directly into the moist soil like wheat, corn or cotton and does not need continuous submergence so it reduces overall water requirement also. Precision leveling is desirable, it increases water efficiency, improves crop stand and optimize input use.

Economics of DSR: A field study by Rice-Wheat Consortium, in India indicated that comparative economics of DSR and puddled transplanted rice showed that in 67 per cent cases the farmers obtained either higher or equal yields from DSR as compared to traditional puddled transplanted rice. The 33 per cent of farmers having lower yields were due to inexperience of the farmers such as seeding in inappropriate soil moisture, deeper seeding than there cm, delayed and improper use of herbicides. The study also showed that comparative to puddle transplanted rice, the saving in DSR was $70-102 per ha. The zero tillage induced savings in DSR were mainly through reduced cost in land preparation (77 per cent), irrigation water (15 per cent) and labor (eight percent). Thus the overall benefits of DSR are that it saves labor, fuel, time, water besides being cost effective and gives higher net returns as compared to conventional puddled transplanted rice. The DSR has now become part of conservation agriculture all over the world by various national and international organizations had initiated in sustaining crop and water management in rice-wheat system. DSR with laser land leveling significantly decrease cost of production, enhance soil health, save water, matures earlier, increase yields and income.

In Pakistan, the traditional puddled rice transplanting in rice-wheat cropping system is followed for the last over 2000 years. Seedlings 4-6 week old are transplanted in puddled fields. Puddling is achieved by ploughing fewer than 10-12 inches of standing water. It is a soil management operation that reduces soil permeability, controls weeds, facilitates transplanting of rice seedlings raised in nurseries and reduces deep percolation losses of water to maintain anaerobic condition in rice. Nearly 30 per cent of total water requirement of rice is consumed mainly in puddling and transplanting operations, besides additional water is required for raising rice seedlings in nurseries. Continued puddling over the decades has led to deterioration in physical properties of soil through structural break down of soil aggregates and capillary pores and clay dispersion. Puddling forms a compacted layer (plough plate) that restricts percolation of water causing temporary water-logging which restricts root penetration and growth of succeeding crops after rice.

Industrialization in the rice zones has further caused shortage of labor for timely transplantation of rice thus resulting in reduction of yield. The declining water resource base has further compounded the situation. Therefore, besides improving our water resource base, there is need to find an alternative technology that is more water efficient, less labor intensive. One such technology is direct seeding of rice (DSR) instead of the traditional puddle transplanted rice. As it avoids puddling and does not need continued submergence and thus reduces overall water requirement for rice cultivation. But traditional agronomic practices used in DSR cultivation cause several problems to farmers such as poor germination, high early seedling mortality during a rainfall event, requiring gap filling in uneven fields, weed infestation and non-availability of effective post and pre-emergence herbicides. However, improved practices to overcome these problems have been developed now.

The salient features of DSR technology are as follows:

·        Advantages of DSR:

·        Labor saving up to 75 %

·        Water saving up to 30 %

·        Early maturity of crop

·        Timely sowing of wheat crop

·        Saving of machinery operations (needed for puddling)

·        Avoids compaction of soil due to puddling

·        Good precursor of zero tillage technology for wheat crop.

PRODUCTION TECHNOLOGY:

The land should be laser leveled and prepared to produce a leveled seedbed with fine tilth free of weeds. Fine seed bed ensures better yield because of good germination and crop stand, root proliferation, fertilizer efficiency.

Planting Techniques and seed rates:

The best planting time of DSR will be 10 to 12 days earlier than the traditional transplantation period which will enable earlier planting of the following wheat crop resulting in its increased yield as against its traditional late sowing in wheat-rice system, especially for basmati rice which due to its longer period further delays sowing of succeeding wheat crop and a delay of one day after third week of November results in reduction of its yield by 35 kg per ha per day. Again, due to aerobic soil conditions under DSR, as required by the following wheat crop, there is no need of a number of ploughings required for changing the anaerobic to aerobic soil conditions of rice grown under traditional puddled transplanting system. Thus the zero tillage technology for sowing of wheat after DSR may be more effective. Zero tillage technology directly sows wheat seeds and applies fertilizer in one operation in the residual moisture of harvested rice stubbles. Thus it not only further reduces the delayed sowing of wheat but also saves rauni irrigation (irrigation given for seed bed preparation), cost of preparatory tillage and increasing wheat yield due to its earlier planting. According to observations at field conducted by the Directorate of On Farm Water Management (OFWM), Punjab, which introduced zero tillage in the country, it saves irrigation water by 20 per cent and increases wheat yield by 15-20 per cent.

Sowing is done in moist soils using latest inclined plate multi crop planter 9? row spacing. Fields should be irrigated when nursery planting time begins and properly prepared for planting. Seed rate and seeding depth: The seed rate for direct seeding of medium to fine grain rice varieties should be 12-14 kg per acre. Higher seed rate can reduce yield by causing nitrogen deficiency, reduced tilling, increase in the number of ineffective tillers, increased attack of brown plant hoppers and crop lodging. Seed depth should be 2-3cm for good crop stand. Placing seed below 3cm adversely affects dynamics of seed emergence because of rapid drying of soil surface in peak summers. If seed is soaked for 8 to 10 hours it advances germination. Soaked seed (priming) is dried in shade to decrease its moisture content which facilitates its free flow during seed drilling by advanced inclined plate multi crop planter. Soaking of seed with fungicide eliminates or reduces seed borne and soil born diseases like Bakaini.

 Sowing Time: 

The best planting time for DSR is 10 to 15 days before crop transplantation. This, coupled with the fact that DSR matures 10-12 days earlier, enables early planting of the following wheat crop. Seeding too early causes crop sterility due to high temperature at anthesis; seeding late exposes the crop to heavy attack of insect pests and diseases. For fine rice, the crop should be sown from end May to 3rdweek of June, and for coarse varieties, mid May to early June.

Fertilizer Application: 

Adequate and timely application of fertilizer is a prerequisite for good yields. Optimum quantity of fertilizer needed depends on the nutritional status of the fields; however, a generalized  recommendation of fertilizer use consists of 2 bags urea, 1.5 bags DAP and 1 bag potassium sulphate (SOP). All P and K, 1/3rd of N should be drilled along with the seed; the remaining N can be applied in two splits; 1/3rd after 25 days of sowing and 1/3rd after 40-45 days. In areas where zinc deficiency occurs zinc must be applied as zinc sulphate (35% Zn) @ 5 kg/acre. Leaf color chart (LCC). Critical LCC value of three (3) is used for fine Basmati rice varieties. Value of LCC should be recorded after 20-25 of direct seeded rice up to its heading. It is recommended to apply a little more of N and P to DSR

Irrigation Management:

 Irrigation is critical in DSR especially at earlier stages. Unleveled fields cause wastage of land and low irrigation efficiencies, resulting in lower wheat yield. Nearly 20-25 per cent of water is lost during irrigation on unleveled fields and farm designing. Thus use of laser land leveling technology on unleveled fields will minimize cost of land preparation, save irrigation water, obtain uniform seed germination, increase fertilizer use efficiency and increase crop yield. Soil must be kept moist for the first 12 days to ensure complete germination. DSR crop does not require continuous submergence and can be safely irrigated when hairline cracks appear on the soil. In DSR water is only given to keep soil continuously moist. Moisture stress should be avoided at tillering, panicle initiation, and grain filling stages which are crucial for obtaining higher yields. At these stages it is advisable to keep fields flooded. The last irrigation should be applied 20 days before harvesting. DSR is an aerobic rice production and may show iron deficiency symptoms in some soils. Flooding or submerging the field corrects these symptoms.

Weed Management:

Weed control: Weeds are a major concern for high productivity of DSR crop. Weed control efficiency depends on timely operations particularly during early growth stages of rice. In DSR fields, weeds are a major challenge. Weed control through adequate land preparation, judicious use of water, and use of appropriate herbicides is, therefore, essential. The crop should be kept free of weeds during the first 40-45 days after that weeds will not influence yields adversely. Flooding is very effective in controlling all weeds and avoiding iron deficiency. It is, therefore, advisable to flood fields for 10-12 days after emergence of the crop. Following herbicides can give good weed control applied at proper time and manner.

Success of DSR depends on effective weed control

Herbicides

Rate

 (ml/acre)

Application

(days after planting)

Pendimathalin (Pre Emergence)

1000ml

Immediate after Seed Drilling

Venessta. Post emergence (Byspyribic Sodium+ Bensosulphuron)

80gm+80ml

15-25 days after seeding

Puma Super Post Emergence (Phenoxyprop)

350ml

25-35 days

Venessta has given good results for weed control in DSR. So it can be used as post emergence herbicide alone in 2 applications one after the other as necessary. Madhana (Dactyloctenum aegyptium) proves a difficult weed extensively found in non-core rice areas. It spreads out fast and can cover wide areas in the field. It can be controlled with Pandimathalin at early stages. Post emergence weedicide like Venessta (Bensosulphuron+Byspryibic sodium) if the weed advances its control with rice weedicide is difficult. Puma super (Phenoxyprop), a wheat crop weedicide can provide effective control. Rice crop is, however, sensitive to Puma super, so it should be applied 25-35 after planting when crop has established and Madhana is in early stage. A dose of 350ml/acre should suffice.

However, the yield of aerobic rice is comparable with transplanted rice and it has been reported from several countries. Thus, it is an alternative option to reduce labor drudgery and to increase water productivity. Further, in environmental point of view, emission of methane is lower substantially in aerobic rice.

Therefore, in recent days it is gaining momentum among rice researchers and farmers. However, extra care should be taken, since poorly managed field may cause partial to complete failure of crop, which might ha