The influence of sowing furrow opening and wetting and drying cycles on soil physical quality under no-tillage in Southern Brazil

Abstract

Soil disturbance from seed drilling and fertilizer application promotes structural changes that impact the physical quality of soil under no-till (NT). This study tests the hypothesis that spatial and temporal changes to crop rows and interrows along the occurrence of wetting and drying cycles promote changes in soil physical quality under NT.Undisturbedsoilsamples weretaken from0.0−0.10mand0.10−0.20m depthsinaRhodicFerralsol underlong-termNTon fivesuccessive dates,fromwithintherow(R),interrow(IR)andanintermediatedistance betweentherowandinterrow(IP).Inadditiontothespatialandtemporalvariationofthesamplingposition,the occurrence of wetting and drying cycles (WDC) was considered. The undisturbed samples were used to determinesoilbulkdensity(BD), soilwaterretention andpenetration resistancecurvesandthe leastlimitingwater range (LLWR). At the 0.0−0.10 m depth,there were systematically lowerBD at the Rposition than at the IRand IP, whereasforthe 0.10−0.20m depththere werenodifferencesamong the sampling positions.The LLWRwere significantly higher for R compared with IR and IP, suggesting more favourable soil physical conditions for plants at the R position. For the different sampling dates, it was found that there were significant variations in the physical quality of the soil at 0.0−0.10 m while slight variations regardless of the sampling position were verified at the 0.10−0.20 m depth. The changes in soil physical quality within crop rows as well as due to the WDC were only verified at 0.0−0.10 m depth. The WDC impacted the soil physical quality at the IR and IP positions, while soil disturbance during the drilling improved soil physical quality at the R position. The absence of soil disturbance and the reduced magnitude of WDC did not alleviate the soil compaction at the 0.10−0.20 m depth. The temporal variation of rows and interrows induced by crop rotation in areas under NT seems to be a mechanism that alleviates surface soil compaction. In fields managed under NT, the identification of sampling positions, especially of R or IR areas, is fundamental for the proper interpretation of soil physical quality indexes given that R and IR dynamics over time can modify the soil physical properties.