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Technologies to Improve Rice Yield




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    RICE is the country’s second staple, high-valued and major export crop. But there has been a decrease in area and size of the crop in recent years. Lower production especially of Basmati varieties is due to heavy rains in lower Sindh and in Punjab at the time of maturity of the crop. The better prices offered by millers for sugar cane crop last year is also the reason for shifting of the area to sugar cane crop.

    Despite high-yielding varieties and resource conservation technologies in use, there has been decrease in the crop area and yield. This necessitates research through constant involvement of farmers and sharing of findings among them. Weed control, rainfall pattern, sufficiency of water supply, field elevation and hydrology are the major determinants of farmer?s choice for rice production method. In addition, wage rates, availability of family labour, and power for land preparation were found to be the major economic factors influencing the choice of cultivating methods.
    Transplantation is the most common method in rice cultivation. Rice plants raised in a nursery bed are transplanted into puddled and leveled fields 15 to 30 days after seeding. Rice seedlings can either be transplanted manually or through machine. Land preparation activities in the main field begin with pre-saturation irrigation to saturate the topsoil layer and to create a pounded water layer (about 5cm in depth) for land soaking, followed by ploughing and puddling (harrowing under saturated soil conditions). Puddling is done not only to control weed, but also to increase water retention, reduce soil permeability, and ease field leveling and transplanting. After land preparation, the crop growth period in the main field goes from transplanting to harvest. This traditional transplantation requires high continuous water inputs and labour at a critical time, which often results in shortage and increase labour costs.
    Traditional method of raising rice nursery is by using pre-germinated seeds usually after soaking them into water for 48 hours which makes them ready for transplanting within 40-45 days of sowing. Better quality seeds produce vigorous seedlings with increased growth rate and high percentages for germination. The seedlings become ready within 30 to 35 days. Improved method of raising nursery is by using primed seeds treated with CaCl2 and KCl for both coarse and fine varieties of rice. This treatment helps improve growth, yield and quality of the transplanted rice.
    Excessive use of nitrogen (N) leads to crop lodging, invites insect pests and diseases, pollution of water sources and ultimately loss of yield and grain quality. Simple tool to optimize nitrogen application in rice is use of leaf colour chart (LCC). An attractive technology to increase production after harvesting the crop is to take a ratoon crop as in the case of sugar cane can also be practiced in rice as an alternate to double cropping in areas where water is available after the main crop season. Better yield from a ratoon crop greatly depends on agronomic and management practices of land preparation, sowing date, adequate plant density and spacing, use of appropriate cultivars, water management, application of adequate rate of fertilizers, appropriate height of cutting, and control of diseases, insects and weeds. These interactions are needed to be studied properly for manipulating ratooning ability agronomically.
    Area under Chinese hybrid rice has increased. Producers of hybrid rice predict that it will reach 8,57,143 acres by 2012, admitting that the entire production would be for export. For growing high quality paddy from hybrid rice needs the following steps: seed from previous crop should be discouraged, healthy nursery seedlings should be transplanted, seedbed should be properly prepared, optimum dose of fertilisers at right time should be applied and right amount of water at a depth of 2-3cm should be maintained. Proper plant protection measures and timely harvesting of crop at maturity make hybrid rice production different from farmers? usual practices. Production of hybrid rice seed from China would usher Pakistan in a new era in rice production. Under the changing socio-economic environment, there is need of a method that results in high yield and involves use of fewer inputs than in the traditional methods i.e. water, chemical fertilizers or agro-chemicals.
    In this regard, system of rice intensification (SRI) is a new method to be introduced in the country. It involves use of certain management practices, which provide better growing conditions for rice plants, particularly in the root zone, than those for plants grown under traditional practices. Cultivation of any variety of rice under the rice intensification system (SRI) has resulted in at least double yield. No external inputs are needed for a farmer to benefit from SRI. The methods should work with any seed that is being used now. However, what is needed is to have an open mind about new methods and a willingness to practice them. Key success in SRI involves early transplantation of nursery seedlings with first two leaves between 8 t0 15 day raised on moist soil instead of constant flooding. Seedlings should be transplanted singly rather than in clumps of two or three or more in a square pattern usually at 25x25cm space to reduce competition among plants. The square pattern also facilitates weeding.
    One thing that should be taken care is that the soil must be kept moist but not saturated during the vegetative growth period. Later, after flowering, 1-3 centimeter of water is kept standing on the field. However the field is drained completely 25 days before harvesting. In addition to these principal practices, weeding and organic inputs practices are extremely beneficial when using SRI. Many experimental trials have been carried out at the University of Agriculture, Faisalabad, on this system. However, there is need of more on-farm research experiment to verify this new method of increasing rice yield.
    Direct-seeded rice (DSR), an alternative to transplanting, is grown like any other upland crop with seed placed in the soil by seed cum fertilizer drill with or without ploughing. Direct-seeded crop grows faster, reduces labour, crop matures early by 7-10 days, water use is more efficient with less methane emission and often-higher profit in areas with an assured water supply. Many seed priming techniques such as osmo-hardening, hardening and on-farm priming have been employed to enhance the performance of direct-seeded rice under field condition. Agricultural scientists through direct-seeded crop employing seed priming techniques in many on-farm research trials at various fields and the research area of crop physiology department of Faisalabad Agricultural University have obtained improved emergence, better growth, yield and quality of rice.
    Osmo-hardening with calcium chloride and potassium chloride have been found the most promising and effective seed priming techniques to improve performance of direct-seeded rice. Other management and agronomic requirements for DSR is same as in case of puddle-transplanted rice. For optimum nitrogen application an LCC value of three and four is used for scented and other rice cultivars. One or two light irrigations are required to facilitate emergence and afterwards irrigation can be applied at an interval of 7-10 days depending upon the soil type and weather conditions. Weed is a major issue in direct-seeded rice and scientists are making efforts to eliminate this menace. Weed management early in rice season hold key for a successful DSR crop. If it rains before seeding, or it takes time to seed after pre-sowing irrigation, most weeds would germinate early. Pre-germinated weeds can be eliminated with chemical treatment or by 1-2 very shallow ploughings. Experiments have shown that weed problem can be tackled efficiently by integrated weed management practices. Growing of rice varieties (Basmati type) have greater ability to compete with weeds.
     
    By: Hafeez ur Rehman, Dr M. Farooq & Dr S.M.A. Basra

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