ABSTRACT

Considering the cost of two common agriculture inputs, water and nitrogen as well as their effects on the environment, optimum use of them is necessary. In this way, the production functions are applying to achieve maximum profits and environmental protection. Therefore, spilt-plot experiments were conducted on onion (Allium cepa L.) in a completely randomised block design for two years (2014/15-2015/16) in an arid region of Iran. The treatments included three irrigation methods (subsurface drip irrigation (SDI), drip irrigation (DI) and furrow irrigation (FI)), four levels of irrigation water (50(I₁), 75(I₂), 100(I₃) and 120(I₄) % of crop water requirement) and four levels of nitrogen fertiliser (25(N₁), 50(N₂), 75(N₃), and 100(N₄) % of crop nitrogen requirement). Regression analyses were done by linear, Cobb-Douglas, Quadratic and Transcendental functional forms of onion production. Results showed that the quadratic fits the data best, for the given local condition. The onion reached the highest increase in yield rise by increasing a unit of I (irrigation water) and N (nitrogen fertiliser) in SDI and the lowest in FI. Moreover, the pressurised irrigation methods are found to be advantageous to the substitution of N by I. The marginal rate of technical substitution demonstrates that in comparison to FI, more amounts of I and N are required to achieve equal yield in the pressurised irrigation methods.

摘要

考虑到水和氮这两种常见的农业投入物的成本以及它们对环境的影响，有必要对它们进行优化利用。这样，生产功能正在应用以实现最大的利润和环境保护。因此，在伊朗干旱地区以完全随机区组设计对洋葱（Allium cepa L.）进行了为期两年（2014/15-2015/16）的裂区试验。处理包括三种灌溉方法（地下滴灌（SDI）、滴灌（DI）和沟灌（FI）），四个灌溉水位（50（I ₁）、75（I ₂）、100（I ₃）和 120(I ₄ ) % 的作物需水量) 和四种水平的氮肥 (25(N₁ )、50(N ₂ )、75(N ₃ ) 和 100(N ₄ ) % 的作物氮需求)。通过洋葱生产的线性、Cobb-Douglas、二次和超越函数形式进行回归分析。结果表明，对于给定的局部条件，二次方最适合数据。通过增加 SDI 中的 I（灌溉水）和 N（氮肥）的单位和 FI，洋葱的产量增加幅度最高。此外，发现加压灌溉方法有利于用 I 替代 N。技术替代的边际率表明，与 FI 相比，加压灌溉方法需要更多量的 I 和 N 才能实现相同的产量。