Addition of amendments to restore a compacted soil under no-tillage system

ABSTRACT. The addition of organic and inorganic amendments can improve soil structure and reduce soil compaction. In this context, this study aimed to evaluate whether the application of amendments reduces penetration resistance (PR) in the short term and describe the spatial variability of PR in the surface horizon of an Aquic Argiudoll under no-tillage in northeast Argentina. Four treatments, consisting of surface applications of 7.5 Mg ha−1 poultry litter (PL), 3.0 Mg ha−1 gypsum (G), the combination of PL+G, and untreated control (T), were arranged in a complete randomized block design with three replications. Two more treatments were added to the experiment 12 months later, consisting of PL reapplications on half of the surface of the PL+G and PL treatments (PL+G+PL and PL+PL, respectively) in a split-plot design with three replications in 4×20-m plots. PR was determined in the field with an Eijkelkamp penetrologger following a 2-m long transect perpendicular to the sowing direction at 10 different spots separated 0.2 m from each other. The spatial variability was quantified for each treatment using semivariograms. The highest PR was observed in the T treatment (1.96 MPa) and the lowest PR in PL+G+PL (0.21 MPa). All treatments showed a high spatial dependence (94.9 to 99.9%). Treatments with PL reapplication (PL+PL and PL+G+PL) showed profiles with lower PR and more homogeneous kriging maps. PL reapplication on PL treatments showed no effects on PR values. However, PL reapplication on the PL+G treatment led to positive effects in all PR ranges. Thus, the PL+G+PL treatment, which had the highest PR values, showed a decrease in PR from 54.17 to 6.65% with the reapplication 12 months later. The addition of organic and inorganic amendments reduced specific compacted soil areas on the surface horizon of an Aquic Argiudoll under no-tillage.

摘要。有机与无机改良剂配施可改善土壤结构、缓解土壤板结。本研究旨在评估改良剂施用能否在短期内降低土壤穿透阻力（penetration resistance, PR），并刻画阿根廷东北部免耕模式下水成性粘化软土（Aquic Argiudoll）表层土壤穿透阻力的空间变异特征。本试验设置4个基础处理：分别为地表施加7.5 Mg·ha⁻¹家禽有机肥（poultry litter, PL）、3.0 Mg·ha⁻¹石膏（gypsum, G）、PL与G配施，以及空白对照（untreated control, T），采用完全随机区组设计，设置3次重复。试验开展12个月后，新增2个裂区处理：在PL+G与PL处理的一半地表区域追加PL，分别记为PL+G+PL与PL+PL，于4×20 m样地中设置3次重复。采用Eijkelkamp土壤穿透仪（Eijkelkamp penetrologger）开展田间PR测定：沿垂直于播种方向布设2 m长样带，在间距0.2 m的10个测点完成数据采集。利用半变异函数（semivariograms）量化各处理的空间变异特征。结果表明，空白对照处理T的PR最高（1.96 MPa），PL+G+PL处理的PR最低（0.21 MPa）。所有处理均表现出较高的空间依赖性（94.9%~99.9%）。追加PL的处理（PL+PL与PL+G+PL）的PR剖面特征表现为更低的阻力值，且克里金插值图（kriging maps）更为均质。在PL处理基础上追加PL对PR无显著改良效果，但在PL+G处理基础上追加PL则可在全PR区间产生正向改良作用。其中初始PR最高的PL+G+PL处理，在12个月后追加PL使PR从54.17%降至6.65%。综上，有机与无机改良剂配施可降低免耕模式下水成性粘化软土表层的板结土壤面积占比。