Response of Snap Bean to Irrigation, Nitrogen Fertilization, and Plant Population1

Snap bean, Phaseolus vulgaris L., yield was increased by higher plant population, more frequent irrigation, and additional N applied as a topdress. Highest yields were obtained with the irrigation-fertilization program that included applications of 8 mm of water at 23 mm of pan evaporation until 1/3 foliage cover, at 15 mm of pan evaporation until 2/3 foliage cover, then at 8 mm of pan evaporation until harvest with N applications to maintain petiole NO 3 -N level above 1500 ppm preblossom and 1000 ppm during fruit development. Response of 30 × 8 cm and 91 × 3 cm plant spacings to irrigation and N fertilization were similar. Pan evaporation data can be used to schedule irrigation under varied climatic conditions and maintain a low soil water tension throughout snap bean growth. The relationship of water use by snap bean to pan evaporation changes with crop development. An adjustment must be made to compensate for the changing relationship; and frequent irrigation and N fertilization must be made to snap beans produced on sandy soil under humid conditions.