Akademik Veri Yönetim Sistemi
NUTRIENT CYCLING IN AGROECOSYSTEMS, cilt.72, sa.3, ss.279-286, 2005 (SCI-Expanded)
Phosphorus (P) deficiency is invariably a common crop growth and yield-limiting factor in unfertilized soils, especially soils high in calcium carbonate, which reduces P solubility. Even when such soils are fertilized, adsorption and desorption lead towards a reversion to stable and less soluble P forms, thus reducing fertilizer use efficiency. Field trials that examine the implications of such P reactions and residual fertilizer P responses in the field are relatively rare in Mediterranean environments. A 5-year field experiment in southern Turkey examined the residual effects of repeated P fertilizer applications for corn production in a calcareous soil Typic Xerofluvent. Following the initial year's fertilization (0, 33, 66 and 99 kg P ha(-1)) to establish a range of soil P levels in subsequent years, the main plots received 0, 9, 18, 27 and 36 kg P ha(-1) annually. Grain P uptake was calculated for each year and used in the prediction of P recovery. All plots were sampled and analyzed for available P prior to planting with a local corn hybrid. Soil P values increased with the initial P levels (8 - 24 mg kg(-1)) but declined after 3 years ( 6 - 10 mg kg(-1)). Only the lowest annual P application rate ( 9 kg P ha(-1)) produced an available P level that was not in the sufficiency range. Grain yields across the main and subplots and years ranged from 6.6 to 13.2 t ha(-1). Overall corn yield averaged over the years increased by 8 - 33% compared to the control as the rates of applied P increased. However, P application had no effect in a year when below-average rainfall restricted crop growth. A residual P effect on grain yield occurred with higher P application levels in the last year. Leaf and grain P concentrations were in the sufficiency range in general. Grain P uptake was calculated for each year and used in the prediction of P recovery. Actual recovery was higher with low P application rates and ranged between 10.8 and 46.4%. The study indicated that under irrigated conditions, corn is likely to respond to P fertilization, but that buildup of available P can occur within a few years and adequate plant available P levels can be maintained by modest P fertilizer application rates.