Plant Spatial Arrangement, Light Capture and Water Consume in Maize (Zea mays, L) Crops in Soils at Different Landscape Positions.

During the last decades, favorable international prices of commodities and changes in climate variables (i.e. precipitation) promoted an intensification of agriculture production in Argentina. Current technologies, such as yield monitors, global positioning systems guidance and satellite images allowed site specific managements, especially those for heterogeneous lands. In the Argentinean Pampas, groundwater table depth may vary (i.e. from 80cm to >200cm) which is reflected in the potential of soils for grain production. For these heterogeneous environments is necessary to select the most suitable husbandry for agriculture production. In grain crops, canopy structure (plant population, row spacing, and genotype) determines the capture of aerial (i.e. light) and soil (water, nutrients) resources, which is reflected on biomass production and grain yield. Among cultural practices, plant population density has the most impact on these variables, and row spacing may contribute to increase resource capture especially under more restrictive environments. Field experiments were conducted at the west Pampas of Argentina. A single maize hybrid was cultivated under rainfed conditions, in a split-split-polt design, with three replicates, with the landscape position (hillslope, shoulder slope, and footslope) as the main factor, plant population (from 3.5 to 8 pl m^-2) as the sub-factor and row spacing as the sub-subfactor (0.38m, 0.52m and skip-row; i.e. 0.38-0.76m). Available soil water (from 0 to 2m, with 0.2m interval), green leaf area per plant and plant biomass were recorded at ca. silking and physiological maturity, and maximum light capture and specific nitrogen content were measured at the former ontogenic stage. Grain yield response to plant population density varied among landscape positions. Optimum plant populations were 3.5, 6 and 8 pl m^-2 for hillslope, shoulder slope and footslope, respectively. Row spacing did not modify water uptake nor light capture. Narrow rows, however, decreased grain yield probably related to decreased radiation use efficiency.