Aggregate stability and soil surface sealing in irrigated soilsunder no-tillage versus conventional tillage

The effect of no-tillage (NT) (zero tillage) versus conventional tillage (CT) has beenevaluated in rainfed conditions but has seldom been studied under irrigation, wheresoil sealing favours soil degradation. To contribute to this knowledge, this researchanalyses soil aggregate stability under disaggregation forces produced under irriga-tion (causing slaking and mechanical breakdown) and the susceptibility to soil sealingin soils cropped with irrigated maize. Soils were sampled from 0 to 2 and from 0 to5 cm before maize planting. Soil aggregate stability against both disaggregation pro-cesses was expressed by the mean weight diameter (MWD). Soil organic carbon(SOC) was evaluated in aggregates of different size fractions that remained after thedisaggregation processes. Soil sealing susceptibility was characterised by the satu-rated hydraulic conductivity. The results confirmed the high disruption effect of slak-ing and mechanical breakdown processes. The MWD under those processes was upto 50% smaller and the susceptibility to seal was about three times higher in the soilsunder CT than under NT. The results of the top 0–2 cm layer showed an aggregatestability against mechanical breakdown 30% smaller than the 0–5 cm layer, whichcould be due to the soil surface sealing caused by drop impact. Greater MWDs wererelated to higher SOC values in the aggregates, which were about 20% higher in thesoils under NT than under CT. Thus, NT represents an effective management in irri-gated soils, reducing soil sealing and helping to maintain greater aggregate stability insoil surface against the disaggregation forces caused by drop impact and wettingprocesses