Simulating Growth and Yield Responses of Sorghum to Changes in Plant Density
Though numerous field experiments have been conducted on the effects of plant density on growth and yield of sorghum [Sorghum bicolor (L.) Moench], tests showing the ability and validity of a sorghum simulation model to respond to changes in plant density have not been reported previously. Thus, a field experiment was conducted at ICRlSAT Center, Patancheru, India, in the 1983 rainy season on a Vertisol (fine, clayey, montmorillonitic, isohyperthermic Typic Pellustert) to test the validity of the sorghum simulation model, SORGF, for simulating the effect of plant density on growth and development of sorghum. Simulations were compared to data collected on phenology, leaf area indices (MI), total dry matter (TDM), and grain yield for five plant densities (4, 8, 12, 16, and 20 plants m−2) of two sorghum cultivars (CSH 6 and SPV 351). Observed TDM and grain yield increased up to 16 plants m−2, while simulated TDM and grain yield increased up to 20 plants m−2. The model, on average, underestimated TDM by 8% and overestimated grain yield by 2%. Good agreement between observed and simulated LAI, TDM, and grain yield across five plant densities and two cultivars was supported by the insignificant differences of observed and simulated values from a one-to-one line. The model was further validated using climatic data from the ICRISAT Center between 1976 and 1984. Simulated grain yield using plant densities of 12 plants m−2 were within 3% in 6 yr and between 11 and 20% in the other 3 yr of observed data using plant densities of 13 plants m−2. Results from this study suggest that the SORGF model appears useful for simulating the effect of plant density on the growth and yield of wellmanaged sorghum when input data on cultivar, climate, soil, and agronomic management are available.
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