Interactive effects of nitrogen and water stresses on biomass accumulation, nitrogen uptake, and seed yield of maize

Abstract

Although considerable data exist on the growth, development, and productivity of crops in response to nutrients or water applied alone, much less data are available to describe the interactive effects of water and nitrogen. The objective of this study was to determine the interactive effects of N fertilizer and water on biomass (dry-matter) accumulation, N-uptake, and seed yield of maize ( Zea mays L.) growing on sandy soils. Field-grown maize was subjected to three water management treatments: (1) optimal irrigation; (2) a 10-day wilting period immediately preceding silking (vegetative stress); and (3) rainfed. Within each water management treatment, two N treatments were imposed: (1) low N, consisting of a total of 11.6 g N M −2 applied in three side-dress applications; and (2) high N, consisting of a total of 40.1 g N m −2 applied in six side-dress applications. The effects of water and N stress on the crop were determined by growth analysis and measurements of N uptake made throughout the growing season. 3ow soil N significantly reduced leaf area as a result of reduced leaf size, but had little effect on the final number of leaves produced. However, both water and N stress lengthened the time from emergence to tasseling and silking. Accumulation rates of total biomass, seed weight, and N showed interactions with water and N. With high N, the 10-day wilting period preceing silking reduced biomass and seed yields by 22% and 19%, respectively, while the rainfed treatment resulted in 66% and 75% reductions. Low N also reduced biomass and seed yields in both the optimal irrigation and vegetative stress treatments. However, with severe water stress, N level had no effect on total crop biomass, N accumulation, or grain yields. When high N levels were applied, water stress reduced the efficiency of N utilization. With high N, crop N uptake in the optimal irrigation, vegetative stress, and rainfed treatments amounted to 67%, 53%, and 26% of that applied, respectively. With low N, the optimal irrigation and vegetative stress treatments accumulated N amounts near that applied. When severe water stress was imposed in combination with low N, only 60% of the applied N was accumulated by the crop. Nitrogen deficiency did not improve drought resistance of field-grown maize, as has sometimes been suggested.