Gesso mineral no condicionamento de subsolo e na produção de sorgo em Pernambuco

Abstract

Subsurface acidity in Brazilian soils is one of the main factors that cause crop yield reduction and is closely related to high concentrations of Al3 + in depth in the soil. An effective and viable alternative to reduction or elimination of subsurface acidity is to apply gypsum in the soil. In this sense, the objective of this trial was to investigate the effects of gypsum application and time of contact in the soil chemical (Ca, Mg, K, Al, SO42-, pH water e pH CaCl2) and physical (water aggregate stability, MWD, GMD, SAI and micro and macroporosity), assess possible changes in different Al pools (amorphous Al, organic matter bound Al and crystalline Al) and productivity, nutrient uptake (Ca, Mg, K, S, P and N) and agrotechnological variables of sorghum influenced by rates of mineral gypsum. A field test was set up in randomized block design. It was evaluated the application of 0, 2, 4, 6 and 8 t ha-1 of gypsum at three depths (0.0-0.2, 0.2-0.4 and 0.4-0.6 m) in four times [before applying gypsum (0), 15, 64 and 90 days after applying gypsum] to the chemical characteristics of the soil. 5 months after gypsum application soil physical characteristics was evaluated. In plots that received 0, 4 and 8 t ha-1 of gypsum and at 0 and 15 days after application Al forms in the soil were evaluated and was evaluated the effect of gypsum rates in the production, nutrient uptake and agrotechnological characteristics of sorghum. Mineral gypsum application promoted changes in soil chemical characteristics throughout the soil profile (0-0.6 m) by raising the levels of Ca and SO42- and reduced, in the subsoil, Al3+ concentrations and its saturation. It not promoted K+ and Mg2+ leaching and did not promote changes in soil aggregation and stability. Increasing the time of mineral gypsum contact with the soil, greater effect of its performance was observed mainly the rise in exchangeable Ca in subsurface. There was increase of amorphous forms of Al in the subsurface, reduction of forms bounded to organic matter and there was no interference in the crystalline forms of Al in the soil profile. It was observed increase in Ca uptake and reduction in K uptake, besides increasing sorghum productivity. There was no interference in the agrotechnological variables of sweet sorghum.