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In an Arkansas mineral soil with pH of 5.7 and testing 59, 14, and 84 kg/ha of N, P and K, respectively, two cultivars of vegetable amaranth (Amaranthus tricolor L.), `Hinn Choy' and `RC 241' were grown in a fertilizer (3N × 3K × 4P) field experiment. Fertilizer P accounted for 90% of leaf fw yield variations, followed by K, 3%; and N, 2%. Multiple regression equations summarize the yield responses: Yhc = .528 + .00658 N + .146 P − .0000293 N2 − .001537 P2 + .0001351 N*P + .0001854 P*K, R2 = .964 Yrc = .63 + .2085 P − .001349 P2 + .0003497 P*K, R2 = .954 where Y = mt/ha, N, P, K = kg/ha of N, P and K. Fertilizer levels maximizing yields, and optimum levels under varying fertilizer cost/crop price situations were estimated using the derivatives and cost/price ratios. In RC estimated Pmax = 101 kg and estimated Popt = 93 kg at $1.33/kg P and $66/mt of crop.
Abstract
Pruning roots of transplants of onion (Allium cepa L. cv White Grano) to 0.64 cm and tops to 7.6 cm reduced plant top growth 50% and bulb yields 29%. Yields from large transplants were 58% greater than from small and 11% greater than from medium size transplants. Bulb yield was closely correlated with top growth (r = 0.79**). The bulb/top weight ratio at harvest was increased by pruning and by increased transplant size. Within pruning treatments bulb yields were correlated with top fresh weight. Depth of planting had no consistent effect on top growth, bulb shape, sun burning, or yields, but there was some tendency for bulbs to be longer when planted at 7.62 cm than at 2.54 cm depth. Top growth and bulb yield were similar with transplant spacings of 7.62 and 10.16 cm.