Gypsum is used in agriculture as calcium (Ca 2+) and sulfur (S) source, and to mitigate native toxic levels of aluminum (Al 3+). However, the effects on soil chemical attributes, corn leaf nutritional status, grain yield, and profitability should be better understood. Gypsum rates (0, 3, 6, 9, and 12 Mg ha −1) were applied at once (2009) or split in two (2009-2010) or three (2009-2010-2011) annual applications, to a Typic Hapludox under no-till from Southern Brazil. The use of gypsum increased Ca 2+ and S-SO 4 2− and reduced Al 3+ levels in the soil up to 0.8 m depth. Increasing gypsum rates reduced Mg 2+ levels up to 0.6 m. Corn leaf concentrations of Ca and S were increased, while Mg concentration was decreased by gypsum use. The maximum technical efficiency (MTE) rate of gypsum for corn (2013/2014) grain yield was 6.34 Mg ha −1. The most profitable rate for the period 2009-2014 growing seasons was achieved with 4.60, 5.63, and 6.08 Mg ha −1 of gypsum applied at once or split in two and three annual applications, respectively. The use of gypsum within the MTE interval improves chemical attributes in the soil profile, corn leaf nutritional status, corn grain yield, and land use profitability. The use of gypsum causes soil Mg 2+ leaching. Split application reduces leaching process for S-SO 4 2− , but not for Mg 2+ .

The residual effects of gypsum rates and the interaction with N-fertilization on soil fertility, black oat root growth and aboveground biomass yield under no till lacks information. This study evaluated soil chemical attributes up to 0.8 m depth and aboveground biomass of black oat in a continuous no-till area as affected by gypsum rates (0, 3, 6, 9 and 12 Mg ha −1) and topdressing N-fertilization (0, 50 and 100 kg ha −1) to a Typic Hapludox in Southern Brazil. Black oat root growth was also evaluated for two gypsum rates (0 and 6 Mg ha −1) and all N treatments. Gypsum application increased Ca 2+ and SO 4 2 −-S fraction and reduced Mg 2+ levels in all soil layers, and N-fertilization increased NO 3 − and NH 4 + levels in the soil. Gypsum increased root length, superficial area and volume up to 0.8 m depth, while N-fertilization reduced root growth attributes in soil layers between 0.4 and 0.8 m depth. Gypsum increased (quadratically) the aboveground biomass yield of black oats in the two growing seasons, as did N-fertilization, but no interaction between gypsum and N-fertilization was observed. Gypsum can be used to improve soil fertility attributes, black oat biomass and root growth under no till. The higher N-fertilization (100 kg ha −1) increased black oat yield and reduced root growth in depth. In the average of the growing seasons, the gypsum rate of 7.36 Mg ha −1 applied 54 months earlier, associated with a rate of at least 50 kg ha −1 of N (urea) applied at the beginning of black oat tillering achieved the higher aboveground biomass yield.

Under continuous no-till, gypsum has been successfully used to manage soil fertility and improve crop yield. Nitrogen (N) fertilization is critical for crop performance, however, since it is expensive and potentially pollutant, it must be correctly applied. Both subjects have been widely studied, yet there is a lack of information on the interaction between them, especially concerning crops in rotation or succession. The objectives of this study were to evaluate topdressing N fertilization (0, 50, and 100 kg N ha −1 ) on black oat (Avena strigosa Schreb.) under no-till, inside a long-term gypsum experiment (0, 3, 6, 9, and 12 Mg ha −1 ). We evaluated black oat regrowth after haylage harvest and nutrient concentration and uptake by aboveground biomass, as well as the effects of this system on the successor crop soybean (Glycine max (L.) Merr.) in terms of leaf nutrient concentration and grain yield over two growing seasons. The gypsum application, even up to 44 and 55 months earlier, presented a long-term effect when associated with N fertilization, causing black oat biomass to increase during the regrowth phase. Nitrogen fertilization increased black oat regrowth biomass, even without gypsum. Greater nutrient uptake by black oat regrowth occurred under higher gypsum rates and N fertilization, which may have been advantageous in the long term for the production system, once nutrient cycling may partially substitute fertilizer-derived nutrients. Soybean yield was not affected by either long-term gypsum or N applied at black oat tillering, even though some leaf nutrient concentrations were influenced.

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Neste estudo, foram avaliadas doses de alumínio (Al3+) no substrato de enraizamento, quanto ao crescimento, nutrição e qualidade de mudas clonais de erva-mate. Foram utilizados diferentes níveis de Al3+ incorporados ao substrato na forma de sulfato de alumínio (0,00; 2,25; 4,50; 9,00 e 18,00 g dm-³). Aos 90, 150, 215 e 300 dias após a estaquia (DAE), foram avaliados atributos morfológicos e índice SPAD das mudas. Aos 90 e 300 DAE, avaliou-se a consistência do torrão, peso de matéria fresca e seca de raízes, caule e folhas. Com base nesses atributos, calculou-se o Índice de Qualidade de Dickson (IQD), e com as folhas determinou-se a área foliar e os teores de macro e micronutrientes e Al. O crescimento das mudas foi influenciado pelo fornecimento de Al3+ e pelo tempo. Os valores máximos de diâmetro do colo, altura, número de folhas, matéria seca de folhas e área foliar aos 300 DAE foram observados na dose 9,00 g dm-³ de sulfato de alumínio (SA). O teor foliar de Al foi maior na dose 9,00 g dm-3 de SA, e os teores de Ca e K foram reduzidos em função da aplicação das doses de SA. A qualidade (IQD) foi afetada positivamente pelo fornecimento de Al3+, aumentando até a dose 9,00 g dm-³ de SA. Foi possível concluir que a dose de 9,00 g dm-³ de sulfato de alumínio no substrato proporcionou os melhores resultados na produção de mudas clonais de erva-mate.

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