Rice, the staple food for nearly half the world’s population, is unique in its adaptability to different methods of establishment and water regimes. Rice crop establishment varies from region to region and includes transplanting, broadcasting or direct seeding, and drilling. Transplanting is practiced in about 80 per cent of the rice area of South and Southeast Asia, and therefore has received considerable attention in terms of its management and culture.
Presently, about 75 per cent of global rice is produced under irrigated conditions. The expansion of irrigation area in the recent years, the availability of short duration high yielding rice varieties, and high labor cost and cost efficient herbicides have motivated the Asian farmers to shift from transplanting to broadcast seeding of irrigated rice.
Instead of raising seedlings, and uprooting, bundling, and transplanting them in the rice field, the farmers simply soak the sacks containing the rice seeds for about two days. Then they keep it in open air for about 24 hours for draining purposes. The farmers then broadcast the pre-germinated rice seeds into the puddled fields. This technique is known as a faster method of growing a rice crop among the farmers. These are the salient features of wet seeding.
As far as the extent of its adaptability in Asia is concerned in the last few years, wet seeding on puddled fields has been adopted by farmers in the Philippines. In Central Luzon which is the prime rice growing region of the country, adoption of direct seeding has increased tremendously in the dry season. Similar developments are reported in Thailand and Malaysia. Even in temperate climate countries such as Egypt and Korea where transplanting was the only system being practiced for a long time, farmers are now switching to direct seeding.
The benefit derived from direct seeding in this rice cultivation method is that a shorter time is needed for land soaking and land preparation than in transplanted rice, reducing field water losses and saving water. Experimental results from the Philippines suggest about 36 per cent of water is saved in direct seeded plots during land preparation period compared to transplanted service area due to faster land preparation and sowing. In normal irrigation period, water use efficiency was 90 per cent for direct seeding as against 60 per cent for transplanting. The findings also showed that the average yield obtained from direct seeding was significantly higher than that from the transplanted method and it required less amount of water. About 35 per cent and 44 per cent of water was saved for transplanted and direct seeded rice under saturated and continuous standing water conditions. It was also derived that direct seeded rice could tolerate more water stress than the transplanted rice. The economic benefit of adaption of direct seeded rice was remarkably higher than of the transplanted rice due to significantly less labor requirement and higher yield.
Consequently, farmers in higher land elevation and water short areas adopted more direct seeded rice. The increase in the direct seeded service area under irrigated agriculture requires delineation of the area and provision of special water delivery schedule during land preparation period. Some constraints for adoption of this are lack of knowledge about direct seeded rice and perfect land leveling, and water management requirements during crop establishment (ensuring drainage facilities and adequate water delivery) as well as more prevalence of weeds especially during the early crop establishment period. These are some of the constraints for the adoption of direct seeded rice. More attention should go to reducing socio-economic and biophysical constraints. Farmers prefer relatively higher elevation land with less possibility of water logging to adopt direct seeding method of rice crop establishment.
Its relevance to Nepal is that the outstanding challenge to rice researchers and irrigation professionals in the third world countries, including Nepal, is to develop technologies which will increase and sustain rice production to meet ever increasing food requirements. Water is a scarce resource for rice production, especially so in the dry season. It is true that the method employed to make the crops stand and stable, grain yields with direct seeding is sometimes difficult. Also heavy rains following seeding disturb the stand of rice. If seeded into standing water, algae infestation often affects the survival and growth of rice seedlings. Clear water is essential if the rice is direct seeded, because poor crop stand results if a film of mud settles over the seed. Also higher depth of water reduces the crop stand.
As a big number of Nepali youths are leaving the country daily for employment and the food demand is growing, the challenge is to produce more food with less labor and water. Direct wet seeding of rice could be a viable technology to address this problem. Likewise, technologies like Alternate Wet and Dry Rice cultivation along with the System of Rice Intensification are some other options to solve the problem.
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