Dynamics of organic matter and soil quality in agricultural production systems

Author(s)

Deyvison de Asevedo Soares

• Document type: Doctoral Thesis
• Press: Ilha Solteira. 2021-08-17.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Engenharia. Ilha Solteira
• Defense date: 2021-06-07
• Advisor: Marcelo Andreotti; Ieda de Carvalho Mendes

Abstract

Increasingly, the pressure of human activities on the environment, over time, has brought up potential problems that need to be solved at the local level, so that it is possible to reverse environmental problems on a global scale. In this scenario, integrated Crop-Livestock systems (iCL) brings together a set of activities that aim to optimize food productivity while recovering and improving the physical, chemical and biological quality of the soil and the environment, with economic gains. The objective of this study was to evaluate the effects of management systems on the physical, chemical, biochemical attributes and dynamics of soil organic matter, by physical and chemical fractionation, in sandy Cerrado soil. Also evaluate corn grain yields (GY), the potential of intercropped forage for later soil cover, as well as the PG of soybean in succession. The soil in the experimental area was classified as Red Latosol, sandy texture, located in the Caiuá municipality, São Paulo. The experiments were conducted during the 2016/17, 2017/18 and 2018/19 seasons. The experimental design was in randomized blocks, with seven treatments and four repetitions, the treatments were: S-CRUZ: corn + Urochloa ruziziensis grass (grazing) – soybean; S-CPIA: corn + U. brizantha cv. Piatã grass (grazing) – soybean; S-CPAI: corn + U. brizantha cv. Paiaguás grass (grazing) - soybean; S-CNT: corn (no-tillage) – soybean; S-CCT: corn (conventional tillage) – soybean; S-PIAPERE: soybean – Piatã grass (continuous grazing); S-PAIPERE: soybean – Paiaguás grass (continuous grazing). Soybean was grown in the summer and the intercropping corn with Urochloa in the autumn -winter. In perennial pastures, Nellore steers grazed all year round, while in Intercropping the animals graze after the corn harvest. The forage straw decomposition evaluation was carried in the summer out through of litter bags. Soil enzymatic activity, chemical and physical attributes and soil organic matter (SOM) fractions were evaluated. Higher averages of total and particulate organic carbon were obtained in the SPIAPERE system and lower in the S-CCT, at 0 to 0.10 m depth, which reflected in the surface and subsurface carbon stocks. In all treatments, the soil showed a percentage reduction of the humine fraction. Conservation systems showed the highest levels of humic acids (C-HA) in the 0 to 0.10 m layer, but only S-CPAI was significantly higher than S-CCT. Lower levels of fulvic acids (C-FA) and C-HA prevailed in S-CNT and S-CCT, in the 0.20 to 0.40 m layer. In the final evaluation, the S-CNT, S-CPIA and S-CPAI systems and presented the highest levels of P, the S-CPAI and S-PIAPERE had the highest levels of Mg, SB and CEC in the 0 to 0.10 m layer, S-MPAI had the lowest pH and the highest levels of P, Ca, Mg, SB and CEC, S- PIAPERE presented the lowest pH and highest levels of Ca, Mg, SB and V%, in the layer of 0.10 to 0.20 m. The highest V% in the 0.20 to 0.40 m layer occurred in the S-CPAI. In the 0.20 to 0.40 m layer, the highest levels of B occurred in the S-CRUZ and S-CPIA, and the highest levels of Fe in the S-CRUZ. In the last agricultural year, there were the highest GY of corn in S-CSPD and the highest GY of soy in iCLs (S-CRUZ, S-CPIA and S-CPAI). 23% of the straw was degraded in the first 30 days after chemical desiccation (DAD), 37% at 60 DAD and 70% at 150 DAD. In general, the iCLs had higher humidity and lower soil temperature. There was a predominance of higher enzyme activity in the soil under iCLs, but only Arylsulfatase activity was significantly higher in S-CPIA. ICLs provide coverage for soil protection, benefiting processes involved in nutrient cycling, compared to CTS or NTS. corn intercropped with BRS Paiaguás was more expressive in improving soil quality and crop production, however, the superiority of perennial pastures is emphasized. Continuous conventional tillage should be avoided on sandy soils. Animal grazing with controlled stocking rate does not affect the physical quality of the soil. ICLs contribute to increase the levels of C-HA on the soil surface and tend to increase C-FA, C-HA in depth, and carbon stocks in the soil. (AU)

• FAPESP's process: 18/07625-0 - Dynamics of organic matter and soil quality in agricultural production systems
• Grantee: Deyvison de Asevedo Soares
• Support Opportunities: Scholarships in Brazil - Doctorate