Maximising rice yield

Published June 25, 2007

RICE is our third largest crop in terms of area after wheat and cotton. During 2005, rice was planted on over 6.47 million acres and the yield was about 5.5 million tones. Pakistan is famous for producing and exporting long- and extra- long grain aromatic basmati rice. In addition, it also exports a substantial quantity of coarse rice.

Rice is the second important cash crop after cotton covering 11 per cent of total cropped area. It is a major export commodity after cotton. It earned $1.156 billion foreign exchange during 2005-06. Basmati is the premium rice which fetches $567 per ton as compared to $240 per ton of coarse rice in the international market. About 15per cent increase in export of basmati during 2005-06 resulted in an additional $350 million foreign exchange earning. The share of Pakistan in total world rice trade is around 11 per cent. The provincial shares of Punjab, Sindh, NWFP and Balochistan in the overall rice area is 69, 22, 3 and 6 per cent, and in production 58, 30, 3 and 9 per cent, respectively.

The rice yield in the country is much lower than the potential yield under farm circumstances. The yield gap is due to several biological and socio-economic constraints in the adoption of technology. The production is beset by a number of problems. The major causes are the limited quantity of quality seed, low plant population, Zinc deficiency, imbalanced use of fertiliser, soil salinity, shortage of irrigation water, diseases and insect pest infestation and post harvest losses and socio-economic constraints.

In order to boost rice production and to make the crop more profitable for the growers, rice production technology has been formulated with the following salient features:

Cultivation of approved varieties: It is imperative to cultivate the approved varieties to enhance productivity. The banned varieties i.e., 386, super fine, kashmira and malta should not be cultivated. KS282, IR6 and NIAB-IRRI 9, KSK 133, Super Basmati, Basmati 385, Basmati 2000, Basmati Pak, Basmati 198, Shaheen Basmati, DR 82, DR 83, DR 92, Latefee, Sarshar, Shua-92, Shadab, Khushboo-95, JP-5, Swat-1, Swat-2, Pakhal and Sada Hayat, are the approved rice varieties.

Seed rate: The recommended seed rate is essential to get sufficient number of seedlings per hill for optimum plant population. The recommended seed rate for nursery sowing of basmati varieties is 5-6 kg per acre while for coarse varieties is 8-10 kg per acre.

Optimum time of nursery sowing: Timely sowing of nursery and its transplanting is vital for good yields. The optimum time of nursery sowing and transplanting is given as under:

Paddy seed treatment: Bakanae and Brown Leaf Spot diseases are seed- borne diseases and mainly attack the basmati varieties causing considerable economic loss. To control the above diseases, seed treatment with any suitable fungicide at the rate of 2.0gm per one kg seed is essential.

Methods of raising nursery

Wet seed method: It is commonly followed in Punjab and NWFP. The plot is watered about 20 days before sowing. It helps in eradication of weeds. Fields are ploughed twice followed by planking after one week’s interval. Paddy seed is soaked and pre-germinated seed is then broadcasted in the field.

Dry method: It is usually practiced in Sindh and Balochistan. The plot is prepared under dry conditions. Wheat husk or sugarcane trash is spread uniformly over the plot and burnt. Next day, the ash is mixed in the soil and soaked seed is broadcast followed by irrigation.

Rice nursery management: Sowing of nurseries should be done with regular interval according to the requirement of transplantation. Transplanting of 25 - 40 days old nursery should be done. The nursery is prone to the attack of rice stem borers and grasshoppers, therefore, rice nursery should be treated with any suitable insecticide for obtaining insect-free nursery. First application of any suitable insecticide should be done against grasshopper at ETL which is three per cent damage of the rice nursery. The second application of any granular insecticide should be done at ETL which is 0.5 per cent dead hearts for control of stem borers.

Land preparation: Rice field should be well prepared and levelled to keep the standing water uniform in the field before transplanting of nursery. Two double ploughings in dry condition and two double ploughings in standing water are necessary.

Optimum plant population: The optimum plant population is very important to get a good yield. To establish the optimum plant population, distance between plants and rows should be kept at nine inches. By keeping this distance, about 80,000 plant-hills are established in one acre.

Weed control: Rice weeds may reduce yield by 15-20 per cent but in some cases, losses may go as high as 50 per cent. For good yield, weed control with any recommended herbicide at 3 - 5 days after transplanting is essential.

Use of fertiliser: It is recommended that fertiliser should be applied on the basis of soil analysis. In case of coarse varieties full doses of P and K and half dose of N should be applied with the last ploughing and the remaining half dose of N is top dressed at 30-35 days after transplanting (DAT). For basmati varieties, full doses of P and K and 1/3rd of N should be applied with the last ploughing, 1/3rd of N at 25-30 DAT and remaining 1/3rd of N at 45-50 DAT. Use of potassium where tube-well is the only / main source of irrigation is also recommended.

The following quantity of fertilisers is recommended for different rice varieties:

Application of zinc: The deficiency of zinc appears in all rice varieties. Therefore, it is imperative to apply zinc to get good yield.

Water management: The water depth at the time of transplanting and one week later should be kept low (1-1.5 inch) and, thereafter, it should be gradually increased to about two inches for a period of 20 days. About 25-30 days after transplanting, the field should be kept at water saturated level but do not let it dry and then re-irrigate after the application of nitrogenous fertiliser. Watering should be stopped two weeks before harvesting the crop.

Insect, pest control: The major insect pests here are stem borers, leaf folder and white backed plant hopper which cause about 25-30 per cent losses. Granules should be applied only in those fields which can retain standing water and spray insecticides in the fields without standing water. Grasshopper can be controlled by cleaning of field borders before and during the crop and dusting of hot spots with appropriate insecticide. Various bates are also available for the control of this insect.

For the control of leaf roller, borers and white backed plant hopper rice crop should be thoroughly examined from mid of August to the end of September for insect pest attack. The insecticide application should be done on the basis of ETL which is five per cent dead hearts in case of stem borers, two affected leaves per plant for leaf roller and 20-25 nymphs/adults per plant for white backed plant hopper. The incidence of leaf roller starts from shady places. Therefore, it can be easily controlled with the spot treatment of kerosene oil soaked rope dragging of field also gives effective control of the pest.

Management of diseases: Air-borne diseases i.e., bacterial leaf blight and paddy blast can be controlled by copper based fungicides and blasticides when applied at proper time in proper dose. Seed born diseases can be controlled by seed dressing with recommended fungicide at the rate of 2g/kg paddy seed. Soil born disease i.e., stem rot can be controlled by cultural practices like destruction of rice stubbles and seclerotia deposited in the field corner at the time of puddling.

Harvesting: Optimum time of harvesting is very important for getting maximum paddy yield, good milling recovery and high quality rice. A deviation of 5-10 days from this time seriously affects the paddy yield as well as milling recovery. The optimum time for harvesting the crop is about 35 days after flowering and at a moisture content of about 20-22 per cent. This range of moisture content is indicated when all the ears of paddy have turned yellow, except for a few lower ones which are still green but are filled up with grains.

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