Overuse or underuse of nutrients relative to recommendations is a likely cause of crop yield gaps and an impediment to the achievement of food security. Government-endorsed recommendations are developed to deliver the best evidence-based advice on balanced fertilizer; however, deviations of farmers’ nutrient use from the recommendations are rarely examined. This study chose the salt-affected coastal zone of the Ganges Delta, where low crop productivity and cropping intensity by smallholders limit their income, to determine current nutrient use gaps for the first time of three cropping patterns in two representative districts of Bangladesh. A total of 246 farms were surveyed from three farm sizes. Farmers’ nutrient use gaps were compared with Fertilizer Recommendation Guides published in 2012 (FRG-2012) and 2018 (FRG-2018). Relative to FRG-2012 recommendations, farmers used 12%, 70%, and 11% overdoses of N, P, and K, respectively, under two fully rice-based cropping patterns, but the level of overdoses increased with farm size. Rates of K (14%), S (28%), and Zn use were below the FRG-2012 recommendations, especially for the smallest category of farms. However, the FRG-2018, increased recommended N (5%), K (62%), S (12%), and Zn rates but reduced P (25%) rates for fully rice-based cropping patterns. In contrast with rice, regardless of farm size, farmers applied overdose nutrients to watermelon but compensated with underdoses in the subsequent monsoon rice implying that farmers prioritized fertilizer expenditure on the most profitable crop. For the cropping pattern with watermelon, farmers could reduce the use of N (69%) and P (46%) and increase the use of K (48%), S (5%), and B. Reducing NPK use gaps can save treasury for both the farmers and the governments by 39.1 and 73.8 USD ha^-1, respectively, under fully rice-based cropping patterns. Finally, our findings suggest there is scope to promote crop yields and sustainable intensification through balanced fertilizer use in a vulnerable saline region.

相对于建议而言，营养物质的过度使用或使用不足可能是造成作物产量差距的原因，也是实现粮食安全的障碍。制定政府认可的建议，以提供关于平衡肥料的最佳循证建议；然而，农民的养分使用与建议的偏差很少受到审查。本研究选择了恒河三角洲受盐分影响的沿海地区，该地区农作物产量低且小农的种植强度限制了他们的收入，首次确定了孟加拉国两个代表性地区三种种植模式的当前养分利用差距。共调查了三个农场规模的 246 个农场。将农民的养分使用差距与 2012 年 (FRG-2012) 和 2018 年 (FRG-2018) 发布的肥料推荐指南进行了比较。相对于 FRG-2012 的建议，在两种完全以水稻为基础的种植模式下，农民分别使用了 12%、70% 和 11% 的过量 N、P 和 K，但过量水平随着农场规模的增加而增加。钾（14%）、硫（28%）和锌的使用率低于 FRG-2012 的建议，尤其是对于最小的农场类别。然而，FRG-2018 增加了推荐的 N（5%）、K（62%）、S（12%）和 Zn 施用量，但降低了完全以水稻为基础的种植模式的 P（25%）施用量。与水稻相比，无论农场规模如何，农民对西瓜施用过量的营养，但在随后的季风水稻中用剂量不足进行补偿，这意味着农民将化肥支出优先用于最有利可图的作物。对于西瓜种植模式，农民可以减少氮（69%）和磷（46%）的使用，增加钾（48%）的使用，^-1，分别在完全以水稻为基础的种植模式下。最后，我们的研究结果表明，在脆弱的盐碱地区，通过平衡化肥的使用，可以提高作物产量和可持续集约化。