Common bean yield responses to nitrogen fertilization in Brazilian no-till soils: A meta-analysis

ABSTRACT Although numerous studies have been conducted with common bean regarding nitrogen (N) dose, time of application, and source in no-till (NT) soils in Brazil, the heterogeneity of the results makes it difficult to establish technical recommendations based on individualized studies. This meta-analysis aimed to rank the main factors influencing common bean response to N management in NT areas. The database consisted of 99 scientific papers that encompassed 160 trials and 2394 observations. In general, the probability of obtaining a positive response to N application in common bean productivity was 77 %, with an average 18 % increment (358 kg ha-1). The main factors that affect the response of common bean grain yield to N fertilization and the choice of the applied N dose are soil organic matter (OM) content and the preceding crop. In soils with OM content >20 g kg-1, the N dose that determines the highest economic return is 50 kg ha-1. For soils with OM content <20 g kg-1, the N dose to be applied is 70 and 100 kg ha-1 for crops preceded by legumes and grasses, respectively. The timing of the N application did not result in a significant difference in common bean yield in 62 % of the trials. However, the results showed that the average yield increase in the common bean went from 15 % (293 kg ha-1) with a single application to 32 % (622 kg ha-1) with split N applications. All N sources tested showed similar gains to those obtained with N application through urea. Excluding situations with high doses of N application (>100 kg ha-1), inoculating common bean seeds increased grain yields by 6 % on average (118 kg ha-1). The combined analysis of the available results demonstrated that the crop recommendations used in Brazilian soils under NT could be refined considering the soil OM concentration and preceding crop. Additionally, seed inoculation and N dose splitting in the form of common urea should be recommended.

摘要 尽管巴西免耕（no-till, NT）土壤中针对普通菜豆的氮（N）施用量、施用时期及肥料来源已开展大量相关研究，但研究结果的异质性使得难以基于单项研究制定统一的技术推荐方案。本荟萃分析（meta-analysis）旨在明确免耕田块中影响普通菜豆对氮素管理响应的关键因素。本研究数据库涵盖99篇学术论文，包含160组田间试验与2394个观测值。总体而言，普通菜豆产量对施氮产生正响应的概率为77%，平均增产18%（合358 kg·ha⁻¹）。影响普通菜豆籽粒产量对氮素施肥的响应及最优施氮量选择的核心因素为土壤有机质（soil organic matter, OM）含量与前茬作物。当土壤有机质含量＞20 g·kg⁻¹时，可实现最高经济收益的施氮量为50 kg·ha⁻¹；当土壤有机质含量＜20 g·kg⁻¹时，前茬为豆科作物与禾本科作物的田块，推荐施氮量分别为70 kg·ha⁻¹与100 kg·ha⁻¹。在62%的试验中，不同施氮时期对普通菜豆产量未产生显著影响。但研究结果显示，普通菜豆的平均增产率从单次施氮的15%（合293 kg·ha⁻¹）提升至分次施氮的32%（合622 kg·ha⁻¹）。所有测试的氮素肥料来源均表现出与尿素（urea）施氮相近的增产效果。排除施氮量＞100 kg·ha⁻¹的高剂量场景后，普通菜豆种子接种处理可使籽粒产量平均提升6%（合118 kg·ha⁻¹）。对现有研究结果的综合分析表明，巴西免耕土壤现行的作物施肥推荐方案可结合土壤有机质浓度与前茬作物进行优化。此外，推荐采用普通尿素开展种子接种与分次施氮。