Improving the Drainage and Irrigation Efficiency of Lowland Soils: Land-Forming Options for Southern Brazil

Land leveling is used to correct soil surface irregularities to improve surface drainage and irrigation. It also makes the area more manageable for an array of agricultural activities such as planting and harvesting. The objective of this work was to evaluate two designs of land forming, one aimed at optimizing drainage and the other at optimizing surface irrigation, using fields with reliefs typical of the lowlands of southern Brazil. Seven commercial rice fields, ranging in size from 7 to 26 ha, were randomly selected and digital elevation designs generated for each. Land-leveling projects were developed using three designs: uniform slope (US) (control), land forming-drainage (LFD), and land forming-irrigation (LFI). Performance comparisons between the designs were evaluated through impacts on soil movement (SM), maximum cut in 99% of the area (MC), cumulative length of levees (LL), and total number of levees (NL). Results indicate that both LFD and LFI designs would reduce costs and require less soil disturbance compared to leveling to uniform slopes. LFD would require less soil movement and lower maximum cuts than LFI. However, LFI would reduce the lengths and numbers of rice levees that could have long-term economic and agronomic benefits not captured in these analyses. These results demonstrate that all land-leveling and land-forming alternatives should be thoroughly examined before undertaking field operations. Study outcomes will be useful to engineers and producers in evaluating options to improve the agricultural productivity of lowlands in southern Brazil, a region of national and international significance.