关键词: 水肥耦合类型, 量化方法, 冬小麦, 华北平原, 水氮配置

Abstract:

【Objective】 A novel method for distinguishing quantitatively irrigation and fertilizer coupling types was introduced, and basing on this method, irrigation and nitrogen combination in winter wheat on North China Plain was to be optimized. The aim of the study was to have a greater understanding of coupling effect of water and fertilizer, and to provide theoretical and practical basis for promoting water and fertilizer synergetic management in crop production. 【Method】 The results showed that the difference between the true value and the theoretical value of crop relative yield was statistically significant (P＜0.05) or not was considered as the critical criterion for distinguishing the coupling type of a specific water-fertilizer combination. The two-factor split plot experiment was persistently carried out in the North China Plain in Hebei province during ten successive winter wheat growing seasons (2016-2016). In this experiment, the two irrigation treatments were the main plots, irrigation one time (75 mm in jointing stage, W₁) and two times (75 mm in jointing and flowering stage respectively, W₂) during wheat growing season, and five N rates were the subplots, consisting of 0 (N₀), 60 (N₆₀), 120 (N₁₂₀), 180 (N₁₈₀), and 240 (N₂₄₀) kg·hm ^-2, respectively. The coupling types of different water-nitrogen combinations and their inter-annual variation characteristics were explored to determine the optimized water-nitrogen combination in winter wheat growing seasons.【Result】 When the true value of the crop relative yield of a water-fertilizer combination was statistically higher than its theoretical value, the water and fertilizer coupling type of this combination was “synergism” (water and fertilizer promote mutually). When the true value was significantly smaller than the theoretical value, the water and fertilizer coupling type was “antagonism” (water and fertilizer restrict mutually). When there was no significant difference between the true value and the theoretical value, the water and fertilizer coupling type of the combination was “additivity” (water and fertilizer no interaction). The water-nitrogen coupling type and inter-annual variation characteristics of the W₂Nx combinations in winter wheat were significantly affected by nitrogen application rate. Generally, the water-nitrogen coupling type of W₂N₆₀ was antagonism basing on the average yield of winter wheat in the 10 years. To be specific, for the W₂N₆₀, water and nitrogen antagonized mutually in the first two experimental years, in the 3rd year the relationship between water and nitrogen changed into collaboration until the 5th experimental year, and the water-nitrogen coupling type of the combination was antagonism in the 6th to 10th year. The water-nitrogen coupling type of W₂N₁₂₀ was additivity in the 1st to 4th year, and then turned into synergism in the 5th to 10th experimental year. The coupling type of W₂N₁₈₀ and W₂N₂₄₀, in which nitrogen application exceed 120 kg·hm ^-2, was additivity in each year in the experiment. 【Conclusion】 It is of great feasibility to identify quantitatively the coupling type of a specific water and fertilizer combination based on the significance of the difference between the actual value and the theoretical value of the crop relative yield. Under the combination of W₂N₁₂₀, water and nitrogen promoted yield increase synergistically for a long time. Therefore, maintaining the annual grain yield of 8.5 t·hm ^-2 or so, W₂N₁₂₀ should be recommended as an optimal combination of water and nitrogen for winter wheat in the northern part of the Huang-Huai Plain over a certain period of time.

Key words: water and fertilizer coupling type, quantization method, winter wheat, North China Plain, water and nitrogen combination