Detailed Explanation of the Key Technical Points of Dry Rice Cultivation
Dry rice cultivation is an important method of water-saving rice growing. It skips seedling raising and transplanting, sowing directly in natural conditions after land preparation, relying on natural rainfall throughout the whole growth period to meet the needs of growth, and only irrigating appropriately when drought occurs to ensure high and stable yields. Therefore, dry rice cultivation is also called dry-field rice growing. As long as the "four rationalities" and "one management, one control" are achieved, it will succeed.
1. Rational land selection and preparation. For dry rice cultivation, it is advisable to choose low-lying, easily waterlogged fields or flat fields of water-retentive meadow soil. Sloping and hilly land, and plots with high sand content or severe salinity and alkalinity are not suitable for dry rice cultivation. For land preparation, especially for plots converted from paddy to dry land, mechanical deep ploughing is advocated, followed by rotary tillage, to achieve a level field surface with a firm top and loose subsoil. Land preparation is best done while the soil is still frozen, which can preserve the thawing moisture and improve soil moisture content.
2. Rational variety selection. The varieties required for dry rice cultivation should have the characteristics of drought resistance, cold tolerance, disease resistance, lodging resistance, a moderate growth period and high yield. The growth period should be 10-15 days earlier than that of local varieties.
3. Rational determination of sowing time. The minimum temperature for rice germination is 10°C-12°C. When soil moisture is good, the sowing time should be the main consideration; under drought conditions, soil moisture should be the main consideration. When sowing, press the upper and lower grid marks well. When soil moisture is on the high side, the upper grid marks may be left unpressed to prevent heavy, sticky soil from affecting emergence. Sowing is mainly done by manual drilling; where conditions permit, a wheat seeder can be used, which saves labour and effort and gives good quality. Cover the seed with 2-3 cm of soil. To ensure full emergence, sun the seed for 2-3 days before sowing and treat the seed with chemicals. Seed coating with a special seed dressing agent for dry rice cultivation is advocated, but under drought conditions do not soak the seed, to prevent reducing the emergence rate.
4. Rational close planting. Dry rice cultivation has a short growth period and few tillers, and mainly relies on the main stem to form panicles. Increasing yield through panicles is the main measure for rational close planting in dry rice cultivation. Generally, the sowing row spacing is 30 cm, the sowing rate is 7-9 kg per mu, and 150,000-180,000 plants are kept per mu.
5. Strengthen fertiliser and water management. For dry-grown rice, the role of fertiliser in carrying water is very obvious. The principle of fertilisation is to rely mainly on base fertiliser and supplement with topdressing. The base fertiliser is mainly farmyard manure, with increased application of chemical fertilisers, that is, 60% of the nitrogen fertiliser and all of the phosphorus, potassium and trace-element fertilisers are used as base fertiliser to ensure nutrient supply and promote early and rapid root growth. Topdressing is applied in two rounds, namely tillering fertiliser and panicle fertiliser. If there is no nutrient deficiency, topdressing may be omitted or reduced to prevent excessive vegetative growth and late maturity. The period of maximum water demand and the critical period of water demand for rice coincide with the rainy season in July and August, and in normal years natural rainfall can meet the demand. In special drought years, appropriate supplementary irrigation is needed to ensure high and stable yields.
6. Control of diseases, insects and weeds. Dry rice cultivation also requires attention to the control of bakanae disease, damping-off, rice blast, and pests such as rice planthoppers and rice leaf rollers. To control mole crickets, it is best to coat the seed with a special rice seed dressing agent, or poisoned bait may be used. To make poisoned bait, use 5 kg of soybean cake residue or corn bran per mu, add a little chives and stir-fry until cooked, then add 0.2 kg of 25% chlorpyrifos wettable powder, add 1 kg of water and stir evenly, let it stand for 2 hours, and then scatter it in the field in the evening. For chemical weeding, soil treatment before emergence after sowing to close off weeds is done 5-7 days after sowing, using 200 ml of 60% butachlor emulsifiable concentrate plus 200 ml of 20% oxadiazon emulsifiable concentrate per mu in 75 kg of water sprayed on the soil; post-emergence stem and leaf treatment of weeds is done 5-7 days after emergence and before barnyardgrass reaches the 2-leaf stage, using 200 ml of 60% butachlor emulsifiable concentrate plus 200 ml of 20% propanil emulsifiable concentrate per mu in 60 kg of water for spraying; after the 5-leaf stage, if broadleaf weeds are present, 0.04 kg of 20% MCPA aqueous solution may be used in water for spraying.
Wang Jingqin, Agricultural Technology Extension Service Centre of Yushu City, Jilin Province