the Symposium on Wheats for More Tropical Environments - cimmyt

273Agronomic Practices and Problems forWheat Following Cotton and Rice in PakistanP.R. Hobbs, Wheat Program, CIMMYT, Islamabad, PakistanAbstractThree million hectares ofwheatfollow cotton or rice in Pakistan. To date, littleresearch has been done on <strong>the</strong> agronomyfor wheatfollowing <strong>the</strong>se two majorcash crops on a cropping-pattern basis. Both of <strong>the</strong>se crops delay wheat plantingsignificantly, and results suggest that, from 3 million hectares, 120,000 tons ofwheat are lost for every one-day delay in planting past November 10. Currentrecommendationsfor land preparation, fertilizer use, weed control and varietiesare based on wheatfollowing fallow. Scientists must begin working in teams,ra<strong>the</strong>r than according to commodities or disciplines, to develop more usefulrecommendationsfor cotton-wheat and rice-wheat cropping patterns.Cotton and rice in Pakistan are grownon 2.25 million and 1.8 millionhectares. respectively. in <strong>the</strong> kharif(summer) season. FollOWing harvest, itis estimated that 70% of <strong>the</strong> cotton and80% of <strong>the</strong> rice is followed by wheat.This is equivalent to 3 million hectaresof wheat or 30% of <strong>the</strong> wheat area inPakistan.Unfortunately. most of <strong>the</strong> agronomicresearch on wheat has been done withwheat as <strong>the</strong> sole crop (i.e.. followingfallow), and very little information isavailable on what happens to wheat in<strong>the</strong> double cropping patterns thatinclude cotton and rice. Thiscommentary will. <strong>the</strong>refore. identifyissues for research in <strong>the</strong>se importantcropping patterns ra<strong>the</strong>r than givespecific agronomic recommendations.Planting DateSeeding of wheat is delayed by bothcotton and rice harvest in Pakistan. Theexact timing in cotton-wheat areas isinfluenced by <strong>the</strong> cotton variety(maturity). farmer decision as towhe<strong>the</strong>r to have an extra cotton pickingand <strong>the</strong> ga<strong>the</strong>ring of <strong>the</strong> cotton sticks.which can be a valuable bonus for <strong>the</strong>farmers.In rice. variety is also an importantfactor in <strong>the</strong> delay of wheat planting.Only two rice varieties are cOJ.l1monlygrown in Pakistan. mainly because 40to 50% of <strong>the</strong> rice is exported; <strong>the</strong>refore,<strong>the</strong> government restricts <strong>the</strong>release of varieties. The two varietiesare IR6. a high-yielding. nonphotosensitivetype. and Basmati. atraditional, high-quality photosensitivetype. With IR6. fields are harvested bylate October to mid-November. andwheat can be planted in November;with Basmati. harvest is often delayedto <strong>the</strong> end of November or even intoDecember. In addition. farmers cut. dryand thresh <strong>the</strong> rice in <strong>the</strong> same fieldsbefore turning to land preparation forwheat. This extra 10 to 20-day delayoften pushes wheat planting into lateDecember or even January.Figure 1 shows <strong>the</strong> effect of wheatplanting date on <strong>the</strong> yield of threewheat varieties. The optimal date forwheat planting is November 10 and. onaverage. 40 kg/ha (120.000 tons for 3million hectares) of grain is lost forevery one-day delay in planting afterthis date. Earlier plantings have loweryields because of frost damage duringflowering. ObViously. delayed plantingbecause of cotton and rice substantiallyreduces yield potential. especially withwheat planted after Basmati rice. Thissituation can be improved by usingearlier-maturing cotton and ricevarieties. speeding up turn-around timeand using wheat varieties that yieldbetter when planted late.