ATRIBUTOS FÍSICOS DO SOLO E COBERTURA DE INVERNO SOBRE A DISPONIBILIDADE DE ÁGUA E OS COMPONENTES DE RENDIMENTO DO MILHO

Abstract

Crops such corn (Zea mays L.) are highly influenced by the management practices, soil coverings, sowing dates and local meteorological conditions throughout the crop growing season at a given site. The interaction among such factors will result in dry matter accumulation by the crop that will in turn be converted into productivity. At the assessment of the effects of different planting populations, winter coverings and sowing dates on soil water availability conditioned by the soil physical attributes, as well as on the yield components of the crop, a field trial was carried out at the years of 2014/2015 and 2015/2016 in Ponta Grossa, State of Paraná, Brazil, with P30F53YH as the genotype considered herein. The experimental design was a split plot scheme repeated over three sowing dates (September 15, October 30, and December 15), taking into account three different winter coverings (oat straw, fallow, and bare soil) and five planting populations (40,000; 60,000; 80,000; 100,000 and 120,000 plants ha-1) in the split plots. Morphological features of the plants (plant height, stalk diameter, insertion height of ears, number of leaves, leaf area, and leaf area index) along with yield components (number of rows per ear, number of grains per row, a thousand mass of grains, and mass of ears) plus yield in four plants per split plot were evaluated in the current study. Sequential water balances were performed throughout two crop growing seasons. The soil of the experimental area was characterized, having the soil bulk density and texture been determined and adjusting for the soil layers 0-0.10, 0.10-0.20, 0.20-0.30, 0.30-0.40, and 0.40-0.50 m water retention curves by the model proposed by van Genuchten (1980). From such physical attributes of the soil the distribution of soil total porosity and its classification regarding a more fitting mathematical function were determined. Multivariate statistical methods were used at the analyses of information in order to search for global responses from the studied variables. A sinusoidal model of crop growing was adjusted, which showed a high correlation with the regime of local meteorological elements, allowing therefore for the determination of inflexion points of plant growth rates in height and its relationship with temperature, global solar radiation, soil water availability and net radiation. Significant periods of draught over the course of the crop growing seasons were not observed. Moreover, effects of different soil coverings on corn growing and yield were not detected as well. The final yield and all morphological features of the crop obtained were found to be within the expected standard for the genotype of corn in study. Planting populations affected yield, with increasing values up to planting populations over 120,000 plants ha-1, under which the highest leaf area indices were found. The soil was homogeneous at the entire experimental area and no effect of soil covering on yield components and crop final productivity was identified at all. An interactive effect of sowing dates, planting populations and soil coverings for the sowing dates of October 30 and December 15 (2014/2015) and also for September 15 (2015/2016) on corn yield was observed. Biological yield along with all morphological parameters of the plants were expressed as a result of the genetic potential of the corn genotype at the studied site.