Use efficiency of organomineral fertilizer phosphorus in wheat

This PhD thesis investigates the effectiveness of phosphorus (P) containing organomineral fertilizers (P-OMF) in calcareous/alkaline soils through two greenhouse pot trials and an incubation study under controlled conditions. The P-OMF was formulated by combining an organic fertilizer (OF) derived from a biogas plant with triple superphosphate (TSP), a commercially available mineral fertilizer (MF). The first greenhouse experiment examined the P efficiency of P-OMF compared to P-MF across soils with increasing Olsen P concentrations (10.2, 16.4, and 24.1 mg P•kg-1), assessing agronomic performance and nutrient status of wheat (Triticum aestivum L. cv. Özkan). The second pot experiment and the incubation study were conducted simultaneously to test the effects of different forms (powdered and granular) of P-OMF and P-MF on soil P availability and wheat growth, agronomic traits, and mineral nutritional status of wheat. In both pot experiments, fertilizers were applied 5 cm below the seedbed, while in the incubation study, they were placed 3 cm below the soil surface. Then, two harvests were undertaken: one at the end of the tillering stage and another at the physiological maturity (ripening stage). Two plants in each pot were cut at tillering, and their dry weights were recorded. Also, at the physiological maturity, before the harvest, the morphological traits (plant height and spike length) and number of spikes per pot were taken. Thereafter, the remaining five plants were harvested and dried, and their yield components, such as straw yield, grain yield, and biological yield, were recorded. Grain and straw samples were ground separately and subjected to chemical analyses to determine their N, P, and K concentrations. Nutrient content and uptake values were calculated by multiplying their concentrations in plant samples by the respective dry weights. In the second pot experiment, additional parameters such as SPAD reading, Harvest Index, and Phosphorus Harvest Index were recorded. Concerning the incubation study, soil samples were collected twice, aligning with the harvests of the second experiment: 45 days post-planting (at the tillering stage) and 128 days post-planting (physiological maturity). Finally, soil Olsen P, an indicator of plant-available P, was determined. Results from the first greenhouse experiment revealed that the effectiveness of P-OMF diminished with increasing Olsen P concentrations, particularly for spike count, shoot dry weight at tillering, grain yield, and total plant P uptake including P contents in grains and straw. Conversely, the second greenhouse experiment and incubation study demonstrated that P-OMF applications in powdered or granular forms significantly outperformed MF in terms of grain, straw, and biological yield, as well as grain P content and produced similar or significantly higher total P uptake when applied in powdered and granular forms, respectively.