Agronomic performance and economic implications of maize, sunflower and groundnut sequences on sandy-soil smallholder farms of Zimbabwe
1998
Murata, M. | Hikwa, D.
Two sets of trials were conducted for three seasons, beginning the 1994/95 cropping season, to establish the place of sunflower in the sequencing of crops by smallholder farmers and determine its soil N and P requirements in those sequences. Productivity of the cropping sequences was also measured and economic implications of the N and P rates evaluated on all crops. In the first trial varying rates of P2O5 (30, 60, 90 and 120 kg ha-1) with zero as control, were assessed in crop sequences that were structured such that sunflower would follow two crops of maize (MZ-MZ-SF). In the second trial, three nitrogen rates (30, 60 and 90 kg ha-1 N) were applied to sunflower every year, with non application as the control. The sequences were structured such that beginning with the second season, every cropping season would have the following sequences: sunflower after maize; sunflower after groundnut; maize after groundnut; maize after sunflower; groundnut after maize and groundnut after sunflower. Farm fields selected in Natural Regions (NR) II and IV were classified as deficient in N (20 ppm N) and P (15 ppm P2O5). In the first two seasons sunflower did not respond to applied P. But good responses (P0.01) were observed in the third season, indicating the positive effects of P build-up in the soil. At NR IV locations, maize following another crop of maize performed better than that which followed sunflower at the various P rates, and a similar trend was observed in season three at the NR II location. In sunflower, significant increases in seed yield peaked at the 30 kg P2O5 ha-1 rate. Maize was more responsive to P application, with responses up to 90 kg P2O5 ha-1 recorded in some years.
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