Exploring the Potential of Cowpea-Wheat Double Cropping in the Semi-Arid Region of the Southern United States Using the DSSAT Crop Model

Abstract

Information is limited on the potential of double-cropping cowpea (Vigna unguiculata L.) and wheat (Triticum aestivum L.) in the semiarid region of the southern United States. Using the Decision Support System for Agrotechnology Transfer (DSSAT) crop model and weather data of 80 years, we assessed the possibility of cowpea-wheat double-cropping in this region for grain purpose as affected by planting date and N application rate. Results showed that the possibility of double-cropping varied from 0% to 65%, depending on the cropping system. The possibility was less with systems comprising earlier planting dates of wheat and later planting dates of cowpea. Results indicated that cowpea-wheat double-cropping could be beneficial only when no N was applied, with wheat planted on October 15 or later. At zero N, the double-crops of cowpea planted on July 15 and wheat planted on November 30 were the most beneficial of all the 72 double-cropping systems studied. With a delay in planting cowpea, the percentage of beneficial doublecropping systems decreased. At N rates other than zero, fallow-wheat monocropping systems were more beneficial than cowpea-wheat double-cropping systems, and the benefit was greater at a higher N rate. At 100 kg N ha −1 , the monocrop of wheat planted on October 15 was the most beneficial of all the 94 systems studied. Results further showed that fallow-wheat yields increased almost linearly with an increase in N rate from 0 to 100 kg•ha −1 . Fallow-wheat grain yields were quadratically associated with planting dates. With an increase in N rate, wheat yields reached the peak with an earlier planting date. Wheat yields produced under monocropping systems were greater than those produced under double-cropping systems for any cowpea planting date.

The El Niño-Southern Oscillation (ENSO) Effects on Cowpea and Winter Wheat Yields in the Semi-Arid Region of the Southern US

“…For the scenarios comprising wheat planted before October 15 or October 30 following cowpea planted in June or July, respectively, either the ENSO comparison was not possible because of no feasibility of cowpea-wheat doubling cropping in the study region [70], or, in the cases of feasible scenarios, the d wheat yields were not significantly different across ENSO phases. With a long-term simulation study conducted for the Llano Estacado region using 80 years' weather data, reference [70] found that the number of feasible years for cowpea-wheat double-cropping in the Llano Estacado region ranged from 0 to 52, depending on the double-cropping scenario comprising the planting dates of cowpea and wheat (Figure 8). As they demonstrated, the feasibility was highest, about 65%, with July 15 and November 30 as the planting dates of cowpea and wheat, respectively.…”