Water saving rice cultivation

[uzma khan youzaf zai]

Water saving rice cultivation

By Hafeez ur Rehman and Dr M. Farooq



“DURING the present kharif season, the rice target of 6.4 million tons, against last year’s 6.9 million tons, set by the government seems difficult to achieve due to 7.7 per cent water shortage,” say correspondents from the agriculture department.
This production decline is attributed to reduced area under rice cultivation, depressed prices, rise in fertiliser costs and lower yield per acre.

Rice is commonly grown by transplanting 30- day-old nursery seedlings in well-flooded and puddled fields. In this cultivation system, rice seedlings are raised on separate, well-prepared soil and then manually uprooted and shifted to main field.

Puddling destroys soil structure and even after paddy harvest, plantation of next crop (wheat) is delayed. Poor soil condition developed after continuous standing water is not favourable for better land preparation and good stand establishment. In addition, manual and random transplantation of seedlings ensures optimum plant population and are labour and water-intensive operations, increasing cost of production and resulting in low yield.

Alternatively, aerobic rice is a new water-saving cultivation system in which varieties adaptive to aerobic soil conditions are grown like wheat and maize crops. This system needs 30-50 per cent less water, saves labour and time, and facilitates timely plantation of next crop (wheat). Due to high nitrogen use efficiency up to 50-60 per cent, the next crop is also benefited by residual nitrogen.

Usually rice seeds are drilled or broadcast in fine seedbed at field ca pacity level and subsequent irrigations are applied depending on crop requirement. To avoid weed competition and for vigorous seedling crop stand, seeds soaked in water or primed with CaCl2 may be used.The first irrigation may be delayed until the crop is fully established. For proper weed control during final cultivation, pendimethaline or rhizilon can be applied.

Growing aerobic rice neither needs seed nursery nor transplantation of seedlings. It also does not require puddling operation which reduces cost of production. Research trials at the Pakistan Agricultural Research Council have shown that aerobic rice can double production from the existing 26 maunds to 73 maunds. Nonetheless, aerobic rice can be successfully grown in non-traditional rice belt dominantly with non-basmati varieties on more than 0.9 million hectares. Alternate wetting and drying (AWD) technique in transplanted rice is more appropriate for basmati rice varieties in the traditional rice belt.

AWD is also a water-saving system in which 2-3 weeks old nursery seedlings are transplanted and the field is kept flooded for 35 days and afterwards subsequent irrigation is applied.The field is again kept flooded around flowering.This also saves water by 30-35 per cent and improves productivity.

The two technologies have been verified over the last 3-4 years and are now being practiced in ricegrowing areas of Punjab and Sindh.

Aerobic or AWD technology is being applied in Guranwala, Okara, Kasur and Jhang districts in Punjab and Thatta, and Larkana in Sindh. The total area under such cultivation is estimated at 200,000 hec tares. A team of experts have been engaged to contact farmers and accelerate promotion of water-saving technologies in both the areas.

Demonstration trials for these technologies have shown yield of 6.58 ton per hectare as against 6.82 t/ha with flooded and transplanted rice. Likewise, in basmati rice type, the alternate wetting and drying method saved about seven irrigations over the continuous flooded rice and monitory benefit of nearly Rs9,000/ha.

Under the changing climatic and water scenario, farmers can also practice alternate wetting and drying irrigation scheduling in aerobic rice and reduce weed infestation.

At Faisalabad University of Agriculture researches are being carried out to find optimum water use by nutrient interaction, basmati type evaluation for water saving cultivation and to study the nitrogen and zinc dynamics which occur from a drastic shift from flooding to under water saving cultivation.

Due to alkaline soils, zinc deficiency symptoms occurs both in flooded and aerobic rice and require evaluation of the existing gene pool for identification of rice varieties with the ability to thrive on Zn deficient soils.

Site specific nutrient management, leaf colour chart and split application are some of the technologies to quantify the nitrogen application and improve its use efficiency. While seed treatment with ZnSO4, soil application or foliar application are some of the ways to alleviate Zn deficiency and its loading into grains. Moreover, demonstration by agricultural extension provides an effective media to educate and convince farmers to adopt new technologies.