[Soil physical properties restricting the expression of wheat yield potential in Uruguay] | Restricciones fisicas de suelo para la expresion de altos rendimientos de trigo en Uruguay
1998
Martino, D.L. (Instituto Nacional de Investigación Agropecuaria, La Estanzuela, Colonia (Uruguay))
Soil physical structure regulates the storage capacity and flow of different compounds and energy, and affects crops through four fundamental properties: mechanical impedance, and availability of water, oxygen and energy for root growth. These properties are commonly expressed as mechanical resistance to metal probes, water potential, oxygen diffusion rate, and soil temperature, respectively. The combination of climate, soil types and system of production dominant in Uruguay determine high frequency of occurrence of sub optimal levels of these variables for wheat production. The main problems that were identified are: a) low availability of thermal energy for crop emergence, which determines long seed-emergence periodsb) oxygen deficiency for germination and early deep root developmentc) high mechanical impedance in the upper soil layersd) soil water deficiency during tillering and reproductive phase. Wheat crops are able to compensate yield components to a large extent. Therefore, problems occurring early in the season do not have a large impact on productivity. However, in high-yielding environments, negative effects may occur. On the other hand, water deficiency in later crop stages would more likely impair grain yield potential. In the present work, recent experimental developments are presented, and several hypothesis for preventing and alleviating soil physical restrictions are formulated. The need to improve the currently low rain-water use efficiencies (6-10 kg ha-1 mm-1) by agricultural practices that increase soil water infiltration capacity is stressed.
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