基于产量的渭北旱地小麦施肥评价及减肥潜力分析

【目的】明确小农户经营模式下小麦施肥现状,为实现旱地小麦稳产增产和养分高效利用提供依据。【方法】通过连续5年对渭北旱地1 261个农户的养分管理调研,以维持旱地小麦可持续生产为出发点,基于小麦产量确定的养分需求量,评价农户施肥量,分析农户施肥的问题及减肥潜力。【结果】调研农户小麦籽粒产量介于750—9 000 kg·hm~(-2),平均4 243 kg·hm~(-2),属于低产(2 640 kg·hm~(-2)),偏低(2 640—3 780 kg·hm~(-2)),中产(3 780—4 920 kg·hm~(-2)),偏高(4 920—6 060 kg·hm~(-2)),高产(6 060 kg·hm~(-2))等级的农户依次占22.0%,22.2%,19.3%,22.8%,13.6%。农户氮肥用量介于33—454 kg N·hm~(-2),平均188 kg N·hm~(-2);磷肥介于0—435 kg P_2O_5·hm~(-2),平均125 kg P_2O_5·hm~(-2);钾肥介于0—201 kg K_2O·hm~(-2),平均19 kg K_2O·hm~(-2),农户的施氮、磷和钾量均与小麦产量无显著相关关系。从低产到高产,施氮过量(偏高+很高)的农户比例逐渐降低,由97.8%降低到18.0%;而施氮不足(偏低+很低)的农户逐渐增多,由0.7%增加到45.9%。与氮肥类似,随着产量水平提高,施磷过量的农户比例也逐渐降低,但降低幅度小,由99.3%仅降低到70.9%,即过量施磷普遍存在。与氮、磷不同,在各产量水平下至少有60%的农户施钾不足。因此,在低产、产量偏低水平,重点是施氮量偏高或很高的农户需减肥,减幅在24—144 kg N·hm~(-2)、28%—73%氮肥;在中产、偏高和高产水平,既有减肥,也有增肥,减肥的重点是施氮量偏高或很高的农户,减幅在50—181 kg N·hm~(-2)、26%—51%氮肥,增肥的重点是施氮量偏低或很低的农户,增幅在38—134 kg N hm~(-2)、41%—345%氮肥。针对农户普遍施磷过量的问题,在不同产量水平,施磷量偏高的农户应减少7—31 kg P_2O_5·hm~(-2)、23%—33%的磷肥投入;施磷很高的农户应减少85—118 kg P_2O_5·hm~(-2),61%—85%的磷肥投入。由于钾肥用量普遍不足,施钾很低或不施的农户首先应改变不施钾肥的习惯,根据不同产量水平施用钾肥13—50 kg K_2O·hm~(-2);施钾偏低的农户,应增加7—18 kg K_2O·hm~(-2)、35%—78%的钾肥。【结论】相比于传统的施肥评价中用统一的施肥量标准去评价不同产量水平的农户施肥,本文提出了基于产量的农户施肥评价和减肥潜力分析方法,适于目前中国小农户农田经营模式,可以客观、准确认识目前农户随意和过量施肥的问题,为进行有效调控施肥提供依据。

Yield Based Evaluation on Fertilizer Application and Analysis of Its Reduction Potential in Weibei Dryland Wheat Production

【Objective】It is of great significance to clarify the farmers’ nutrient input situation for the realization of stable yield, high yield, and high nutrient use efficiency in dryland wheat production.【Method】A 5-yr long farm survey of 1 261 farmers was carried out to analyze and evaluate their fertilizer applications and the fertilizer reduction potential in Weibei dryland, based on the nutrient requirement determined by the corresponding wheat grain yields and sustainable development of dryland wheat production.【Result】Obtained results showed the farmers’ wheat yields ranged from 750 to 9 000 kg hm^-2, with the average of 4 243 kg·hm^-2, and they were allocated into five groups as: very low (＜2 640 kg·hm^-2), low (2 640-3 780 kg·hm^-2), moderate (3 780-4 920 kg·hm^-2), high (4 920-6 060 kg·hm^-2) and very high (＞6 060 kg·hm^-2), respectively, accounting for 22.0%, 22.2%, 19.3%, 22.8% and 13.6% of the total. Farmers’ nitrogen (N) application rates ranged from 33 to 454 kg N·hm^-2 with an average of 188 kg N·hm^-2, phosphorus (P) ranged from 0 to 435 kg P₂O₅·hm^-2 with an average of 125 kg P₂O₅·hm^-2, and potassium ranged from 0 to 201 kg K₂O·hm^-2 with an average of 19 kg K₂O·hm^-2. However, farmers’ yields showed no significant correlations with the N, P, and K rates, respectively. With the increase of grain yield levels, the proportion of N over application farmers decreased from 97.8% in the very low yield group to 18.0% in very high group, but that of N deficient application farmers increased from 0.7% to 45.9%, correspondingly. Similar to N, the proportion of P over application farmers decreased from 99.3% in very low yield group to 70.9% in very high yield group, and this means P over application was practiced by more than 70.0% of farmers in each yield group. Different from N and P, K deficient application was practiced by more than 60.0% of farmers in each yield group. Therefore, for N, farmers in very low and low yield groups were recommended to reduce 24-144 kg N·hm^-2, 28%-73% from their high or very high N application rates, and farmers in moderate, high and very high yield groups were recommended to reduce 50-181 kg N·hm^-2, 26%-51% of their high or very high N rates and add 38-134 kg N·hm^-2, 41%-345% more to the low or very low N rates. For P, farmers in different yield groups should reduce 7-31 kg P₂O₅·hm^-2, 23%-33% from the high P rates, and reduce 85-118 kg P₂O₅·hm^-2, 61%-85% from the very high P rates. For K, farmers with no or very low K input in different yield groups were suggested to use 13-50 kg K₂O·hm^-2, and add 7-18 kg K₂O·hm^-2, 35%-78% for those with low K rates. 【Conclusion】 Compared with the conventional method, which adopted an uniform fertilization rate as the criterion to evaluate the famers’ fertilizer application with variable yields, the present work proposed a yield based approach. This approach is proved to be suitable for the small scale household farming in China, and enable to objectively and accurately understand the arbitrary and over application of fertilizer, and to provide a scientific basis for the effective regulation of farmers’ fertilizer application.