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

The spread of no-till has been increasing for several reasons, but most especially, the trend is due to more adequate soil conservation in these areas. Despite this. 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 future practical information to farmers on how to manage the soil compaction as to obtain higher yields. The experiment is located in Ponta Grossa, Paraná --- 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 (2009/2010), and 6) leaf tissue analysis.

Many samples are still in the lab, but results to date suggest: 1) better soil structure quality in the SNT; 2) higher hydraulic conductivity in the SNT; 3) no statistical difference in corn yield for the 2009/2010 crop season; and 4) higher nutrient concentration for the SNT, most especially for P and K. It is important to note that rainfall was adequate and well distributed during the 2009/2010 crop season. 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 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. Brazil-57