This study assessed soil Phosphorus (P) fractions and lability according to crops in rotation and crop residue P inputs under long-term no-till (NT) in weathered tropical soils. Two experiments were established in split-plot designs with fall-winter as the main plot and spring as the subplots. In one experiment, sunflower and triticale were grown in Typic Rhodudalf (TR) soil in fall-winter; in the other experiment, monocropped and intercropped ruzigrass and grain sorghum were grown in Rhodic Hapludox (RH) soil in fall-winter. In both experiments, sunn hemp, forage sorghum, and pearl millet were grown in the spring; an additional fallow treatment was established in spring in TR. Soybean was grown every year in the summer in both experiments. After 12 (TR) and 9 (RH) years, the crop residue quality (e.g. N content and lignin-N ratio) and P inputs of the various crops were assessed. In addition, soil P fractions were determined according to the Hedley procedure. High-quality residue enhanced P recycling by soybean under crop rotation with sunn hemp in both experiments, sunflower in TR, and ruzigrass in RH. Sunn hemp increased soil labile P by 13% compared with pearl millet in TR and by 40% compared with forage sorghum and pearl millet in RH. Forage sorghum in spring enhanced P mod-labile in TR, effect also observed for monocropped grain sorghum and ruzigrass in fall-winter in RH compared to both intercropped. In general, crop rotation under NT improved soil P lability, particularly the biological P pool, suggesting positive impacts from crop residue quality. The results of this study can be used to guide P fertilization strategies for NT cropping systems in tropical soils.

中文翻译：

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集约轮作和残茬质量增加了热带土壤长期免耕条件下土壤磷的不稳定性


本研究根据风化热带土壤中轮作作物和长期免耕 (NT) 下作物残留磷输入，评估了土壤磷 (P) 组分和不稳定性。以秋冬为主区、春季为次区的裂区设计进行了两个实验。在一项实验中，秋冬季将向日葵和小黑麦种植在典型的 Rhodudalf (TR) 土壤中；在另一个实验中，秋冬季在Rhodic Hapludox（RH）土壤中种植单作和间作的紫草和粒用高粱。在这两个实验中，都在春季种植苋麻、饲料高粱和珍珠粟。春季，TR 建立了额外的休耕处理。在这两个实验中，每年夏季都会种植大豆。 12（TR）和9（RH）年后，评估了各种作物的作物残留物质量（例如氮含量和木质素-N比率）和磷输入。此外，根据赫德利程序测定土壤磷分数。在这两个实验中，优质残渣增强了大豆与苋麻轮作、TR 中的向日葵和 RH 中的紫草的磷回收。与TR中的珍珠粟相比，Sunn大麻使土壤不稳定磷增加了13％，与RH中的饲用高粱和珍珠粟相比，增加了40％。春季饲用高粱增强了TR中的磷变化，与间作相比，在秋季的RH中单作谷物高粱和苋草也观察到了这种效应。一般来说，NT下的作物轮作改善了土壤磷的不稳定性，特别是生物磷库，这表明作物残留物质量具有积极影响。本研究的结果可用于指导热带土壤 NT 耕作系统的磷肥策略。