SPATIAL AND TEMPORAL VARIABILITY OF SORGHUM AND CORN YIELD: INTERACTIONS OF BIOTIC AND ABIOTIC FACTORS

摘要

Incomplete understanding of factors affecting spatial and temporal variability of crop yields is one of the reasons for the slow adoption of site-specific farming (SSF). Experiment were designed to describe interactions between biotic and abiotic factors on the spatial variability of grain yield of sorghum and corn and to use this information for managing SSF. Experiments were done using a Low Energy Precision Application (LEPA) irrigation system in 1997,1998, and 1999 for sorghum and in 1998 and 1999 for corn at Halfway, TX. Drought tolerant and susceptible hybrids were grown under high and low water irrigation regimes. Data on plant growth, soil physical properties, soil moisture, pests, and diseases, were collected from geo-referenced points on a30 m grid and analyzed using state-space analysis and stepwise regressions. Water, elevation, soil texture, soil NO3-N, hybrid, plant density, pests and diseases influenced grain yields. The effect of elevation and soil texture on grain yields was seasonally stable and management decisions on variable rate fertilizer and water can be based on this information. The effect of soil moisture, soil NO3-N, hybrid, plant density, pests and diseases on grain yields was seasonally unstable and not easy to predict. The effect of these factors and their interactions with soil physical factors on grain yields can be assessed indirectly through plant growth analysis. Plant height, leaf area index (LAI), and total plant dry matter predicted grain yields of sorghumbetter than that of corn. Information from plant growth analysis can be used for in-season crop management. To successfully implement SSF, biotic and abiotic effects on crop growth and grain yields should be evaluated as a system.