Surface liming and nitrogen fertilization for crop grain production under no-till management in Brazil

Abstract

Supplying a large amount of NO3− in the subsurface can be a strategy to combat subsoil acidity under no-till systems. However, soil acidification caused by ammoniacal fertilizers can increase both aluminum toxicity and lime requirement. A field experiment was performed in the period from 2004 to 2012 in Parana State, Brazil, on a loamy, kaolinitic, thermic Typic Hapludox to evaluate the effects of surface liming and ammoniacal fertilization on soil chemical attributes and yields of crops in rotation under continuous no-till. The region has a mesothermal, humid subtropical climate, with mild summer, frequent frosts during the winter, and no defined dry season. The average altitude is 970m and the annual precipitation is about 1550mm. The treatments consisted of annual applications of NH4NO3 at 0, 60, 120, and 180kgNha−1 to subplots within plots with surface-applied lime previously at 0, 4, 8, and 12Mgha−1, calculated to raise the base saturation in the topsoil (0–20cm) to 40, 65, and 90%. Lime was broadcast on the soil surface in May 2004. The nitrogen rates were applied during the period from 2004 to 2011 in top dressing at tillering of winter crops [black oat (Avena strigosa Schreb.) or wheat (Triticum aestivum L.)], before growing corn (Zea mays L.), soybean (Glycine max L. Merr.) or bean (Phaseolus vulgaris L.) during the summer (2004–2012).Surface-applied lime under no-till was effective in alleviating soil acidity from the soil surface to a 20cm depth. The soil pH increased in the layers below the soil surface to 20cm depth during a 6 years period following surface lime application. Ammoniacal fertilization had an acidifying effect and did not change the effectiveness of surface applied lime to alleviate subsoil acidity. Soil organic matter content was higher in the upper few centimeters under no-till and remained unchanged over time after surface liming and ammoniacal fertilization. Increasing the rate and frequency of ammoniacal fertilizer application increased crop response to surface liming, but did not change the lime requirement to achieve higher crop grain yields. The lime rate estimated by the soil base saturation method at 70% in the 0–20cm depth was appropriate for surface liming recommendation, even when substantial amounts of ammoniacal fertilizer were applied in a no-till system. The results suggest that nitrogen fertilizer use for winter crops could be dramatically reduced in areas under a continuous no-till system, particularly where lime has been applied.