Tropical soils tend to harden during drying due to the generally low content of free-iron and organic carbon, combined with high fine sand and silt proportions. It was hypothesized that the change in soil physical condition induced by the addition of a leguminous mulch in cohesive tropical soil enriched with calcium may mitigate soil hardening through wetting and drying cycles by rain or irrigation, thereby improving the soil rootability. A leguminous mulch was added in different concentrations to a structurally fragile tropical soil enriched with calcium, which then had different irrigation intervals. The treatments were with or without mulch (10 t/ha), with or without added nitrogen (100 kg/ha at 2 intervals) and two irrigation intervals. In 2015 the irrigation intervals were either 4 or 8 days, and in 2016 they were either 6 or 9 days. Two years were used in the attempt to achieve greater differences, as for tested variables, between treatments. Maize planted in these soil treatments was measured for physiological performance, water use efficiency and yield. Mulch used on structurally fragile tropical soil enriched with calcium was found to delay increased penetration resistance from hardening by wet/dry cycles. In this context, an improved soil rootability led to an enlargement of the leaf area index, greater nitrogen uptake and increased CO2 assimilation. This had important physiological consequences due to the positive effect on increased dry matter production and maize yield. In addition, these results suggested that mulch, used with urea, can delay the water supply for 3 or 4 days due to improvements in soil rootability caused by calcium and organic matter interactions. This may be crucial to a region where small intervals without rain are increasingly common due to global climate change. Therefore, due to a greater water use efficiency, this strategy may be a profitable way to increase crop productivity in tropical conditions rather than increasing water and nutrient application alone.

中文翻译：

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通过添加石膏和豆科覆盖物改善粘性热带土壤中玉米的生理和产量响应

由于游离铁和有机碳的含量普遍较低，再加上细沙和淤泥比例较高，热带土壤在干燥过程中往往会变硬。据推测，在富含钙的粘性热带土壤中添加豆科覆盖物引起的土壤物理条件变化可能会通过雨水或灌溉的干湿循环缓解土壤硬化，从而提高土壤的生根性。将不同浓度的豆科覆盖物添加到富含钙的结构脆弱的热带土壤中，然后具有不同的灌溉间隔。处理有或没有覆盖物（10 吨/公顷），有或没有添加氮（100 公斤/公顷，2 个间隔）和两个灌溉间隔。2015 年灌溉间隔为 4 天或 8 天，2016 年为 6 天或 9 天。两年用于尝试在治疗之间实现更大的差异，如测试变量。测量了在这些土壤处理中种植的玉米的生理性能、水分利用效率和产量。发现在富含钙的结构脆弱的热带土壤上使用的覆盖物可以延缓因湿/干循环硬化而增加的穿透阻力。在这种情况下，土壤生根性的改善导致叶面积指数增大、氮吸收增加和二氧化碳增加 发现在富含钙的结构脆弱的热带土壤上使用的覆盖物可以延缓因湿/干循环硬化而增加的穿透阻力。在这种情况下，土壤生根性的改善导致叶面积指数增大、氮吸收增加和二氧化碳增加 发现在富含钙的结构脆弱的热带土壤上使用的覆盖物可以延缓因湿/干循环硬化而增加的穿透阻力。在这种情况下，土壤生根性的改善导致叶面积指数增大、氮吸收增加和二氧化碳增加2同化。由于对增加干物质产量和玉米产量的积极影响，这具有重要的生理后果。此外，这些结果表明，与尿素一起使用的覆盖物可以将供水延迟 3 或 4 天，因为钙和有机质相互作用会改善土壤的生根性。这对于一个由于全球气候变化而变得越来越普遍的地区来说可能至关重要。因此，由于更高的用水效率，这种策略可能是提高热带条件下作物生产力的一种有利可图的方式，而不是单独增加水和养分的应用。