黄土高原苹果过量施氮因素分析

【目的】 黄土高原苹果氮过量施用现象普遍，了解其主要影响因素有利于指导果园科学施肥，提高氮肥利用效率，保障苹果产业可持续发展，推进化肥用量零增长目标实现。 【方法】 通过对黄土高原苹果优势区进行调研和取土，收集了 2012～2013 年苹果产量、收购价格、氮肥用量、生产管理技术和 2013～2014 年的果园土壤有机质含量等指标数据，分别从苹果市场、土壤质量和配套技术采用三个方面对影响黄土高原苹果过量施氮的因素进行了论述，分析了氮肥用量对苹果产量和果实大小 (收购价格) 的影响，果园土壤有机质含量对氮肥用量的影响，不同生产管理技术下的果农采用率和氮肥偏生产力 (PFP_N) 差异。 【结果】 当前黄土高原苹果氮肥用量大，中位数和算术平均值分别为 921 kg/hm2 和 (1032 ± 32) kg/hm2，氮肥过量施用的果农比例高达 90% 以上。果园土壤有机质含量低，中位数和算术平均值分别为 9.8 g/kg 和 (10.2 ± 0.3) g/kg，远低于我国丰产优质果园有机质含量标准 (> 15 g/kg)。随着氮肥用量的增加，苹果产量没有受到显著影响，而果实大小 (收购价格) 却与其显著正相关。随着果园土壤有机质含量的不断降低，果农氮肥用量呈上升趋势，但未达到显著水平 (原因是果园有机质普遍较低，区组间差异较小)。不同生产管理技术间的果农采用率差异较大，其中减氮增效配套技术的采用率普遍低于其他技术。果农间减氮增效配套技术应用效果差异大、技术到位率 (正确的应用方式) 低。 【结论】 苹果市场偏爱大果、果园土壤质量低、减氮增效配套技术普及不足是影响黄土高原苹果过量施氮的重要因素。因此，建立苹果品质评价体系并引导农户，加快果园提质工作的开展，加强减氮增效配套技术的推广力度，是今后我国苹果减氮增效工作的重点方向。

Factors leading to excessive nitrogen fertilization on apple in the Loess Plateau

Objectives] Excessive nitrogen fertilization in apple production is common in the Loess Plateau area of China.Investigating the main influence factors is helpful to guild scientifically efficient orchard fertilization,improve the nitrogen use efficiency,guarantee the development of apple industry sustainably,and promote the realization of fertilizer zero growth goals.Methods] Orchard investigation and soil sampling in the typical apple production areas of the Loess Plateau were used for this study.Indices relating to apple production,purchase price,nitrogen fertilizer rate,production management and technology in 2012-2013 and orchard soil organic matter contents in 2013-2014 were calculated.We analyzed the effect of nitrogen fertilizer rates on apple production and fruit size (purchase price) respectively,the effect of orchard soil organic matter content on nitrogen fertilizer rates,and the grower's technology adoption and difference of PFPN under different technologies from apple market,orchard soil quality and adoption of supporting technologies respectively.Results] The median and mean nitrogen fertilizer rates in tested area were 921 kg/hm2 and (1032 ± 32) kg/hm2,respectively,and the overuse proportion was more than 90％.The median and mean orchard soil organic matter contents were 9.8 g/kg and (10.2 ± 0.3) g/kg,which were far lower than the national standard of high quality organic matter content of the orchard (＞ 15 g/kg).The increased nitrogen fertilizer application did not affect apple yields significantly,but increased the fruit sizes significantly,which was closely related with the price of apple.With the reduction of orchard soil organic matter content,the nitrogen fertilizer rates were on the rise but not significant (the reason was that organic matter in orchard was generally low and the difference between blocks was very small).The adoption rates of the extended technologies were quite different,and the technology of enhancing efficiency but minimizing nitrogen input was the least adopted among the technologies.The effect of the enhancing efficiency but minimizing nitrogen input technology was different among the growers using the technology,and the rate was very low in using the technology in a right way.Conclusions] Preference of big fruits in the apple market,lower soil fertility in apple orchard and limited extension of saving nitrogen techniques were the main reasons for the excessive nitrogen input.Therefore,establishing a good apple quality evaluation system,accelerating the work of orchard soil fertility improvement,and strengthening the extension of enhanced efficiency nitrogen management technologies should be considered in the future.