Soil is a complex system and management practices can significantly affect microbial communities that perform many processes of paramount importance for productivity and sustainability, but there is still no accurate information on their response to gypsum as well as on subsurface consequences. The hypothesis is that gypsum can increase the community of microorganisms in the subsoil, especially in soils that have been fertilized with nitrogen. The objective of this work is to evaluate the microbial biomass after the addition of lime and gypsum in a no-tillage system. An experiment has been carried out on the cultivation of soybean with corn intercropped with Panicum maximum since 2017 and will be followed until 2020. The treatments consist of the application of lime, lime + gypsum and control (without application of correctives) and four N rates (0, 80, 160, 240 kg ha-1), applied to the maize crop. In the plots of the treatment with 160 kg N ha-1 the fertiliser was applied as 15N-enriched ammonium sulfate, to evaluate the fate of fertilizer N. Soil from the experimental area was sampled (0-10, 10-20, 20-40, 40-60 and 60-80 cm depth) prior to the application of the treatments and before sowing the soybean in 2016, 2017 and 2018. It will be sampled again in 2019. The soil solution is being collected by porous capsule extractors for analysis and ionic speciation of Al, Ca, Mg and S. The distribution of the crop root system in the soil profile is being evaluated to a depth of 0-80 cm. The contribution and persistence of straw in the soil will be evaluated periodically, determining the mass of dry vegetable residues and also the N content. The work being carried out in the UK will build on this experiment by studying microbial responses to lime and gypsum addition. Specifically it will investigate the microbial use of C and N and how these additions affect microbial community composition (via PLFAs and MiSeq sequencing) and function (via isotopic tracing).
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