In no till systems liming has been applied to soil surface, causing an excess of lime in the first centimeters of the soil profile, in which N is also applied and root length density is high. The objective of this work was to study N and pH dynamics in the soil profile as affected by liming and N fertilizer broadcast over the straw. Cotton plants (Gossypium hirsutum) were grown for 60 days in pots that received lime incorporated or applied to soil surface. The N was broadcasted at rates of 0, 50, 100 and 150 kg ha-1, as ammonium sulfate. Pearl millet straw was added to soil surface at a rate of 4 ton ha-1. Liming increased N mineralization and nitrification in soil irrespective of lime application method, increasing N availability to cotton and the probability of N leaching. The N uptake by the plants and its immobilization in the microbial mass in the soil neutralized the effect of ammonium nitrogen on soil pH. Cotton responded better when lime was incorporated but this response was not caused by differences in N availability.
Gossypium hirsutum; mineralization; nitrification; soil pH; direct sowing
