CONTEXT

Rice is the primary staple food crop in Nepal, contributing 20% of the agricultural gross domestic product and more than 50% of the total calories in the national diet. Nevertheless, the productivity of rice (3.36 t ha⁻¹) is the lowest in South Asia region.

OBJECTIVE

The objective of this study was to employ a mixed-methods approach to characterize and decompose yield gaps (YGs) in the context of identifying sustainable intensification pathways for rice production in Nepal.

METHODS

Methodologies include: a) landscape-scale crop diagnostic survey on crop management, field attributes, and productivity outcomes combined with gridded soil and daily weather data to decompose rice yield gaps into constituent factors with machine learning diagnostics; b) with survey data, computation of key performance indicators to identify factors associated with productivity, profitability, and resource use efficiencies; c) complementary multi-location on-farm experiments (2011–2017) evaluating new agronomic management practices; and d) dynamic simulation (ORYZA3) to derive estimates of rice yield potential.

RESULTS AND CONCLUSIONS

Analysis of survey data suggests an exploitable YG of 2.57 t ha⁻¹ (40%) and the total YG of 4.85 t ha⁻¹ (55%) indicating substantial scope for increasing rice yields in Nepal. Frequency of irrigation, amount of late-season rainfall, soil type, amount of early-season rainfall, presence of water stress, soil pH, and nitrogen (N) and phosphorus (P) fertilizer rates are the principal determinants of productivity outcomes in descending ranked order. Efficiency metrics suggest rice farmers in the study region make good use of fertilizer inputs, but since application rates are very low (e.g. most farmers apply <20 kg P ha⁻¹) unsustainable mining of soil nutrients is likely common. Farmers in the top 10% of the yield distribution had lower greenhouse gas emission intensities (−43%), increased water productivity (+66%), and higher use efficiencies of N and P fertilizers (+28% and + 20%, respectively), suggesting that yield intensification can be achieved without tradeoffs with key environmental performance indicators. On-farm experiments conducted over several seasons support insights from surveys by demonstrating that major gains in rice yield (1.86 t ha⁻¹) and profitability (US$ 243 ha⁻¹) are achievable through the adoption of good agronomic practices.

SIGNIFICANCE

Through a mixed methods approach, our results suggest that adoption of integrated 'good agronomic practices' can close YGs and improve food security outcomes associated with the rice-based agricultural systems of Nepal while simultaneously preserving or enhancing key sustainability and livelihood objectives.

中文翻译：

---

结合景观尺度的诊断调查，农场实验和模拟，以识别可持续弥合尼泊尔水稻产量缺口的切入点

语境

大米是尼泊尔的主要主食作物，占农业国内生产总值的20％和国民饮食中总卡路里的50％以上。然而，水稻产量（3.36 t ha ^-1）在南亚地区最低。

客观的

这项研究的目的是在确定尼泊尔水稻生产的可持续集约化途径的背景下，采用混合方法来表征和分解产量缺口（YGs）。

方法

方法包括：a）关于作物管理，田间属性和生产力结果的横向作物诊断调查，结合网格化土壤和每日天气数据，以机器学习诊断方法将水稻产量缺口分解为构成因素；b）利用调查数据，计算关键绩效指标，以识别与生产率，利润率和资源利用效率相关的因素；c）评估新的农艺管理方法的补充性多地点农场实验（2011-2017年）；d）动态模拟（ORYZA3），以估算水稻的单产潜力。

结果与结论

对调查数据的分析表明，可利用的YG为2.57 t ha ^-1（40％），总YG为4.85 t ha ^-1（55％），这表明尼泊尔稻米增产的空间很大。灌溉的频率，后期降雨的数量，土壤类型，早期降雨的数量，水分胁迫的存在，土壤的pH值以及氮（N）和磷（P）的施肥量是生产力下降的主要决定因素。排名顺序。效率指标表明研究区域的稻农充分利用化肥投入，但由于施用率非常低（例如，大多数农民施用的磷肥<20 kg P ha ^-1）不可持续地开采土壤养分很常见。产量分布前10％的农民的温室气体排放强度较低（-43％），水生产率较高（+ 66％），氮和磷肥料的使用效率较高（分别为+ 28％和+ 20％） ），这表明可以在不与关键环境绩效指标进行权衡的情况下实现产量增强。数个季节进行的农场实验表明，通过采用良好的农艺方法可实现稻米产量（1.86 t ha ^-1）和获利能力（243美元ha ^-1）的重大增长，从而为调查提供了支持。

意义

通过混合方法，我们的结果表明，采用综合的“良好农艺习惯”可以关闭YG，并改善与尼泊尔以稻谷为基础的农业系统相关的粮食安全成果，同时保持或增强关键的可持续性和生计目标。