Amelioration of soil acidity and soybean yield after surface lime reapplication to a long-term no-till integrated crop-livestock system under varying grazing intensities

• Thirty months after lime reapplication effects were evaluated in the soil profile.
• Three soybean growing seasons with different rainfall were evaluated.
• Grazing does not restrict lime movement through the soil profile.
• Intensive or moderate grazing in integrated system enabling soil correction up to deeper layers.
• Soybean yield is affected by lime reapplication only under severe drought and intensive grazing conditions.

An integrated crop-livestock system (ICLS), with summer grain cropping and winter grazing of cover crops, is an option for agricultural management in subtropical areas. Despite numerous studies evaluating ICLS, there have been limited investigations of soil acidity and lime application dynamics in such systems. Because grain producers resist introducing livestock into cultivation areas due to fear of negative impacts of grazing on soybean yields and lime movement thorough the soil profile, the objective of this research is to evaluate the impacts of surface lime reapplication on the amelioration of soil acidity attributes and the yield of soybean in a long-term integrated soybean-beef cattle system under no-till under varying grazing intensities. An experiment was established in 2001 for an ICLS on a Rhodic Hapludox soil. Crop succession consisted of soybean (Glycine max) cultivation during summer and a mix of black-oat (Avena strigosa) + Italian ryegrass (Lolium multiflorum) during winter. Treatments consisted of varying grazing intensities during winter: intensive grazing, moderate grazing, and no-grazing. Lime was applied to the surface of the entire area at the beginning of the experiment, and a reapplication was performed nine years later (May of 2010) in a sub-parcel scheme (with and without lime reapplication). Soil acidity attributes (pH, base saturation and aluminum saturation) were evaluated at 12, 18, 24, and 30 months after lime reapplication, and the soybean yields of the 2010/11, 2011/12, and 2012/13 seasons were measured. As previously observed for the first surface lime application performed in the same trial area, the present study demonstrated that ICLS, regardless of grazing intensity, did not inhibit soil improvement in deeper layers after surface lime reapplication. In fact, the presence of animals helps to ameliorate soil acidity in deeper layers, compared to non-grazed areas. The soybean yield was not correlated with the soil acidity attributes and was affected by lime reapplication only under intensive grazing and drought conditions. However, when summer rainfall was lower than the expected climatological normal, soybean yields were higher in non-grazed areas.