GrainGenes

ITEMS FROM PAKISTAN

AGRONOMIC RESEARCH STATION

Bahawalpur, Pakistan.

Muhammad Sarwar Cheema, Liaquat Ali, and Muhammad Akhtar.

Wheat following the cotton and rice-based cropping system in Pakistan. [p. 112-113]

Four million hectares of wheat are planted after cotton and rice in Pakistan. Little research has been done on the aronomy of wheat following these crops on a cropping pattern basis. Both of these crops delay wheat planting, and it is estimated that 40-50 kg of wheat grain is lost for every day that planting is delayed past 20 November. Current recommendations for land preparation, fertilizer use, weed control, and varieties are based on planting wheat following a fallow. Team work is direly needed to develop more useful recommendations for planting wheat following cotton- and rice-cropping patterns.

Cotton and rice in Pakistan are grown on 2.93 million and 2.38 million hectares, respectively, whereas wheat is planted on an area of 8.463 million hectares (Fedreal Bureau of Statistics, January 2001). We estimate that 70 % of the cotton- and 80 % of the rice-planted area is followed by wheat. This area equals approximately 4 million hectares of wheat or 50 % of wheat area sown in Pakistan.

Sowing date. The sowing of wheat is delayed by both the cotton and rice harvests in Pakistan. The proper time of wheat sowing is influenced by the cotton variety and maturity. The decision to have an extra picking of cotton and an additional collection of cotton sticks for fuel can be a valuable bonus for the farmer. For rice, the type and variety are also important factors in any decision to delay the planting of wheat. Only two types of rice, coarse and fine, commonly are grown in Pakistan. The coarse-type rice variety IRRI-6, which is a high-yielding, nonphotosensitive rice, is harvested from late October to mid November and wheat can be planted in November, the normal sowing time. Basmati is a fine-type rice often harvested between the end of November into December. In addition, farmers cut, dry, and thresh the rice in the same fields, therefore, land preparation for wheat is often delayed for 15-20 days. Wheat can be planted in December or January. The optimal date for planting wheat is 20 November. On average, 40 kg/ha (160,000 t/4-million ha) of grain is lost for every day planting is delayed after this date. Earlier plantings have lower yields because of frost damage during flowering. Delayed planting after cotton and rice substantially reduces yield potential, especially with wheat planted after Basmati rice. This situation can be improved by using early-maturing cotton and rice varieties, establishing a quicker turnaround time, and using wheat varieties that yield better when planted late.

Land and seedbed preparation. In cotton-wheat areas, seedbed preparation is relatively easy. Following the removal of cotton debris, the soil is relatively friable and can be prepared for wheat quickly. In the rice-growing areas, the situation is different. Approximately one-half of the rice in Pakistan is grown on puddled clay and clay-loam soils. The farmers are faced with a hard, structureless mass of soil to prepare for wheat planting. This preparation takes time and, where soils are heavy in texture, final seedbed preparation may be very poor. Fortunately, the other half of the rice-growing area is medium textured. Associated with the unfavorable soils are the plow pans, developed by puddling and needed to restrict water percolation in rice. For wheat, these pans may limit rooting and subsequent moisture and nutrient availability. They also increase waterlogging in wheat and increase problems with seedbed preparation. If the plow pan is broken, wheat yields may increase, but more water will be required for the rice crop and the soil may not be able to physically support the animals or implements needed to till the puddle soil for rice. As with cotton, there also is the problem of crop residues facing the farmer when he prepares the land for wheat. Little information is available on these issues. More studies are needed to identify and evaluate the best implements for land preparation for their cost and time benefits and their ability to handle residues. A study of the effects of deep tillage on total annual productivity also would be interesting.

Seeding rate and methods of planting. Most farmers broadcast seed for wheat sowing following cotton and rice. The seeding rate usually is 150 kg/ha. More study is needed on using higher seeding rates and to compare broadcast versus machine drilling when wheat is planted late. Poor plant stands are common in the rice-wheat areas, largely because of poor land preparation. A higher seeding rate may compensate for this problem. Studies should also be initiated on no-till planting of wheat into rice as a means to reduce turnaround time.

Fertilizer use. As with the previous agronomic practices, fertilizer studies in Pakistan have been on wheat following fallow, but rarely on wheat following cotton or rice. Response times for nitrogen and phosphorus in cotton­wheat and rice­wheat cropping patterns for different soils must be determined. Reports of response to potash and micronutrients in wheat following rice are available, but more studies are needed in this area on a cropping-pattern basis.

Weed control. Weeds are influenced greatly by the previous crop and cropping pattern. Common weeds in the cotton-wheat rotation include Chenopodium album, C. murale, and Convolvulus arvensis. In the rice-wheat rotation, Phalaris minor and Avena fatua, along with C. album, are the major weeds causing economic losses in wheat. Herbicides could be used to control these weeds. Any phenoxyacetic acid herbicide will control broadleaf weeds, although C. arvensis will regrow after some time. The substituted ureas, Tribunil, Dicuran, Dosanex, or Isoproturon can be used for Phalaris or Avena. Suffix, Mataven, or Difenzoquat may be better herbicides but are more costly than broadleaf herbicides. In Pakistan, herbicide use is in its infancy and few scientists and very few farmers are experts in their proper application. Other methods are needed for weed control. Many farmers rotate land when weeds become a problem. Berseem, Trifolium alexandrinum, is used in place of wheat as a winter fodder when weeds are a problem, however, this is not a viable option except in areas where berseem is a cash crop. Preirrigation is another way of reducing weed populations. The weeds are plowed under just before planting. The major problem here is the delay in planting associated with irrigation, and so this obviously is not a solution for growers of Basmati rice. Many farmers irrigate their rice fields before harvest to germinate weed seeds and not delay wheat sowing.

Yield gap. A substantial yield gap has been observed between yield at the experiment stations and in farmers' fields in each province. This gap is primarily from a lack of finances on the part of a majority of farmers for implementing modern technology for wheat production. Thus, there is great hope for improving wheat production and yield in the country.