Protection of a Unique Ecological Area Through Improved Water and Fertility Management.

摘要

Research was conducted to define practices for managing water and nitrogen fertilizer in the production of irrigated corn on sandy soils. The objective was to increase the efficiency of use of the water resource while minimizing the leaching of nitrate nitrogen from the crop root zone to the groundwater system. On the sandy soils which were studied,experiments showed that it is not necessary to completely replenish the soil water deficit at each irrigation. Near maximum yields were obtained when water application was limited to an amount equivalent to .76cm per day,approximately 60% of the peak evapotranspiration rate. Stored soil water and rainfall supplemented irrigation application. Percolation loss was minimized by this technique. An irrigation frequency of 3.5days during July and August produced greater yields than did frequencies of 1.5or 7days. Research indicated that the present farmer practice of applying 250kg/ha of nitrogen and completely replenishing the soil water deficit at each irrigation may result in nitrate leaching losses of 30to 45kg/ha during the growing season,depending on rainfall amount.