Direct Seeding of Rice (DSR)
In the wake of the lockdown and the exodus of migrants in 2020, there were reports that farmers in Punjab and Haryana were being encouraged to resort to direct seeding of rice (DSR) in place of the method of transplanting.
In the technique of DSR, seeds are directly sown in the field instead of seedlings being transplanted from the nursery.
In conventional practice, seedlings are grown in nurseries and then transplanted on fields that are ‘puddled’ or tilled in standing water using tractor-drawn disc harrows. For the first three weeks or so after transplanting, the plants have to be irrigated almost daily (if there are no rains) to maintain a water depth of 4-5 cm. Farmers continue irrigating every 2-3 days even for the next 4-5 weeks, when the crop is in the tillering stage (stem development). The underlying principle here is that paddy growth is compromised by weeds that compete for nutrition, sunlight, and water. Water prevents growth of weeds by denying them oxygen in the submerged stage, whereas the soft ‘aerenchyma tissues’ in paddy plants allow air to penetrate through their roots. Water, thus, acts as herbicide for paddy. The threat from weeds recedes once tillering is over; so does the need to flood the fields.
In DSR, farmers need to level their land and give one pre-sowing irrigation or rauni. Once the field soil is well moisturised, they need to do the ploughing and planking (smoothening of soil surface), followed by sowing of the seeds and spraying of herbicides.
The practice of DSR involves the use of a tractor-powered machine to sow the seeds. One such machine is the lucky seed drill developed by the Punjab Agricultural University (PAU) in Ludhiana. It can sow seeds and simultaneously spray herbicides to control weeds. It is different from the more popular happy seeder in that it is used to directly sow wheat on combine-harvested paddy fields, containing leftover stubble and loose straw.
In DSR, herbicides are sprayed along with sowing seeds as in this technology, water is replaced by real chemical herbicides.
Herbicides are of two kinds: pre-emergent and post-emergent. Pre-emergent is applied before germination, whereas the post-emergent is sprayed 20-25 days after sowing, depending upon the type of weeds appearing. In the former case, the herbicide used is pendimethalin; while in the latter case, bispyribac-sodium and fenoxaprop-p-ethyl are used.
Benefits of DSR
The most important advantage of DSR is that it saves water. According to agricultural scientists, the first irrigation under DSR is necessary only 21 days after sowing besides the pre-sowing rauni. This is unlike the case of transplanted paddy, where watering has to be done practically daily to ensure submerged/flooded conditions in the first three weeks.
The shorter period of flooding and the lower disturbance of soil in DSR also reduce the emission of methane.
It also saves labour. In order to transplant one acre of paddy in a single day, about three labourers are required. As for yield, it is as good as from normal transplanting.
In DSR technique, after rice harvesting, the management of rice residue and sowing of next wheat crop is easier in comparison to traditional practice. The DSR crop matures 7-10 days earlier, hence provides a wider window for residue management.
With no change in soil structure, the soil remains friable after DSR crop harvest, whereas puddling (transplantation) changes soil structure. As a result, it becomes easier to manage rice residues and sow the next crop in a friable soil.
Drawbacks of DSR
Weeds are a major constraint in DSR-Weeds appearing along with the DSR seedlings prove to be move competitive. Effective weed control is necessary, otherwise yield losses are greater in DSR than in transplanted rice. Herbicides, thus, are essential. The main concern is the availability of the herbicide. If DSR is adopted by every farmer, it would be quite difficult to meet the demand for herbicides.
Another concern is related to the fulfilment of demand for seeds because the seed requirement for DSR is higher, at 8-10 kg/acre, compared to 4-5 kg/acre in transplanting.
There is also the issue of laser land levelling, which for DSR, as it enhances yield besides saving water. Laser-assisted precision levelling of land saves irrigation water, nutrients, and agro-chemicals. It helps improve environmental quality as well as crop yields. This may not be affordable for every farmer.
In DSR, farmers point out, sowing has to be done by the first fortnight of June. The plants should come out properly before the monsoon rains arrive. But in the method of normal transplanting, there is no such restriction because in this method the saplings are previously raised in the nursery.