A Nitrogen and Water Response Surface for Sprinkler-Irrigated Broccoli1
- R. B. Beverly,
- W. M. Jarrell and
- John Letey2
Farmers typically apply large amounts of both N and water in commercial vegetable production. As costs of both inputs increase, and with mounting concern over nitrate leaching and non-point source water pollution, the need for information on optimal management of both resources grows. We investigated the combined effects of five N application rates (0, 87, 190, 255, and 331 kg ha−1) and a continuous irrigation variable (1.14 to 32.9 cm of water, or 0.05 to 1.52 times net pan evaporation) applied by a line-source sprinkler system on broccoli (Brassicu oleracea L., Botrytis group) growth rates and yield. Growth rates generally increased with both water and N treatments, although some interactions emerged. Harvested fresh weights continued to increase throughout the range of treatments, applied, with maximum yields in excess of 20 Mg ha−1. Yield (Mg ha−1 ) responded to N (kg ha−1) and water applied following seedling establishment (cm) according to the equation Y −1.03 + 0.0498 N − 8.73 × 10−5 N2 + 1.23 × l0−3 NW + 0.272 W − 8.20 × W2 where Y is yield, N is nitrogen, and W is water applied after seedling establishment. Analysis of the resulting response surface indicated that under these conditions of frequent sprinkler irrigation (approximately twice weekly), relatively low N rates (140 kg ha−1) provided the lowest combined N and water cost for 10 Mg ha−1) yield. Further, yields increased with higher N and water rates, although quality must also be consideredPlease view the pdf by using the Full Text (PDF) link under 'View' to the left.
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