Abstract No-till management systems tend to cause soil compaction in the early years of their establishment. Soil compaction reduces crop production due to restrictions on root development. Management strategies combining crop rotation and soil conservation practices still need to be researched as potential strategies to mitigate no-till soil physical constraints in tropical regions with prolonged drought periods and still promote agricultural sustainability. The objective of this study was to determine if soil specific management could mitigate early-stage no-till compaction and improve least limiting water range in a Rhodic Ferralsol. We hypothesized that no-till cropping systems with concomitant conservation practices –soil fertilization, crop rotation, and intercropped brachiaria grass– would improve soil physical quality (SPQ) and still achieve high crop yields in a tropical region with dry winters and frequent dry spells during wet season. Six no-till cropping systems were tested: soybean monoculture (T1); corn monoculture (T2); corn and soybean rotation (T3); corn and soybean rotation with intercropped brachiaria (T4); and two more with increased fertilization: corn and soybean rotation with intercropped brachiaria (T5), and corn and soybean rotation (T6). Least limiting water range (LLWR) was used as an indicator of SPQ. LLWR is computed as a function of bulk density (Bd), and it is defined as the range of soil water content in which physical constraints to plant growth are at minimal. Its critical limits are water contents associated with field capacity and air-filled porosity (upper limits), along with wilting point and soil resistance (lower limits). For each Bd, there is a LLWR value: the span between the upper limit and the lower limit. An adaptation of LLWR, in which we substituted the wilting point by the critical water content (θ*), was also tested (LLWR*). Critical Bd (BdC) value was 1.30 Mg m−3 for LLWR and LLWR*. In monoculture treatments (T1 and T2) the maximum Bd values exceeded the BdC (LLWR = LLWR * = 0) and negatively correlated with crop yield. Alternatively, cropping systems with diverse crop rotation (corn/soybean/brachiaria) showed greater values of LLWR and LLWR* and less soil compaction than monoculture systems. Usage of LLWR* evinced water stress was the main limiting plant growth factor; viz. θ* was more limiting than mechanical resistance and deficient aeration. These results support the hypothesis that the use of soil conservation practices and crop rotation during initial years of no-till farming contributes favorably to SPQ without compromising crop production.

中文翻译：

---

土壤管理和多样化的作物轮作可以减轻早期免耕压实并改善 Ferralsol 中最低限度的水范围

摘要 免耕管理系统在其建立的早期往往会导致土壤板结。由于根系发育受到限制，土壤压实降低了作物产量。仍需要研究结合轮作和土壤保持实践的管理策略，作为减轻干旱期延长的热带地区免耕土壤物理限制并仍然促进农业可持续性的潜在策略。本研究的目的是确定土壤特定管理是否可以减轻早期免耕压实并改善 Rhodic Ferralsol 中的最低限制水范围。我们假设免耕种植系统伴随着保护措施——土壤施肥、轮作、和间作臂草——将改善土壤物理质量 (SPQ)，并在冬季干燥且雨季频繁干旱的热带地区实现高作物产量。测试了六种免耕种植系统：大豆单一栽培（T1）；玉米单一栽培（T2）；玉米和大豆轮作（T3）；玉米和大豆间作臂架（T4）；还有两个增加施肥的：玉米和大豆轮作与臂架间作 (T5)，以及玉米和大豆轮作 (T6)。最小限水范围 (LLWR) 用作 SPQ 的指标。LLWR 被计算为体积密度 (Bd) 的函数，它被定义为对植物生长的物理限制最小的土壤含水量范围。其关键限值是与田间持水量和充气孔隙率（上限）相关的含水量，以及枯萎点和土壤阻力（下限）。对于每个 Bd，都有一个 LLWR 值：上限和下限之间的跨度。对 LLWR 的改编，我们用临界含水量 (θ*) 代替萎蔫点，也进行了测试 (LLWR*)。LLWR 和 LLWR* 的临界 Bd (BdC) 值为 1.30 Mg m-3。在单一栽培处理（T1 和 T2）中，最大 Bd 值超过 BdC（LLWR = LLWR * = 0）并且与作物产量呈负相关。或者，与单一栽培系统相比，具有不同作物轮作（玉米/大豆/臂）的种植系统显示出更高的 LLWR 和 LLWR* 值以及更少的土壤压实。LLWR* 的使用表明水分胁迫是主要限制植物生长的因素；即。θ* 比机械阻力和通气不足更具限制性。这些结果支持这样一个假设，即在免耕耕作的最初几年使用土壤保持措施和轮作对 SPQ 有利，而不会影响作物生产。