Soil Physical Properties, Dynamics of N P K and Crop Yield as Influenced by Soil Compaction Under No-Till

The practice of no-till is gaining popularity for several reasons, chief among them being adequate soil conservation in no-till areas. However, soil compaction has been noted as one of the main problems in areas under no-till cultivation for years. Not plowing the soil, plus the traffic of machines in these areas, leads to soil structure alterations resulting in poor soil physical quality and changes in the dynamics of N, P, and K. These conditions can all contribute to crop yield reductions. This project was planned to integrate chemical and physical evaluations of soils under no-till, foreseeing the need for future practical information to be given to farmers on how to manage soil compaction so as to obtain higher yields. The experiment is located in Ponta Grossa, Paraná, under a low fertility, acidic Oxisol high in clay, and under no-till for 20 years. The treatments consist of: 1) maintaining regular no-till system (RNT), and 2) no-till submitted to mechanical sub-soiling (SNT). The study is evaluating: 1) visual soil structure quality, 2) soil water characteristics and soil resistance, 3) soil hydraulic conductivity, 4) air permeability, 5) corn crop yield, and 6) leaf tissue analysis.

Results suggest some temporary improvement in soil physical quality in terms of soil structure and hydraulic conductivity in the SNT treatment as opposed to the RNT. Such temporary improvement, however, did not result in higher yields of corn and soybean. It is important to note that rainfall was adequate and well distributed during the two crop seasons. This may have diminished the possibility for differences between the two treatments, where advantages for the SNT would be expected. The higher concentration of P and K in the plants under the SNT, noticed in the first year, are most likely because both nutrients are transported to the root by diffusion. Thus, sub-soiling provided better conditions for plant root development, which in turn resulted in more P and K contact and absorption, and consequently, higher P and K concentrations in plants. New results for plant analysis are expected at the end of 2012 when this project completes. They might provide some interesting and new insights. Brazil-57