Hybrid squash: Responses to nitrogen, potassium, and phosphorus fertilisers on a soil of moderate fertility

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Abstract
Hybrid squash (Cucurbita maxima L. cv. Delica) was grown at five levels of nitrogen (N) at each of five levels of potassium (K), and at five levels of phosphorus (P) at each of two levels of N at Pukekohe, New Zealand. Destructive samples were taken on three occasions during early growth and fresh weight, dry weight, and nutrient contents were measured. The fruit was harvested, and yields and nutrient contents determined, when the crop was mature. Nutrient supply strongly affected plant growth and tissue nutrient concentrations measured 16 days after emergence. Growth differences were maintained until harvest, but differences in tissue nutrient concentrations declined during growth. Fruit yields closely reflected the differences in early growth, increasing from 29 to 38 t/ha with N additions up to 160 kg/ha, from 25 to 38 t/ha with K additions up to 320 kg/ha, and from 22 to 45 t/ha with P additions up to 320 kg/ha. Yield differences were mainly attributable to fruit number per plant, rather than to fruit size. Nutrient removals in the harvested fruit were up to N 179, K 203, and P 36 kg/ha.