Crop parameters determination of QUEFTS model for optimizing NPK nourishment in wheat

The QUEFTS model is using for optimizing fertilizer managements in crops, but it has not been used in Iran yet. QUEFTS accounts for interactions among NPK affecting the IE of N, P and K and allows differentiation according to different yield levels targeted. It is necessary to determine crops parameters before application the model in the studying area. The first step of the QUEFTS model requires the estimation of the soil-supplying capacity or potential indigenous supplies of N, P and K for a given site or field. In step 2, the actual uptake of a nutrient (UN, UP, UK) is calculated as a function of the potential supply of that nutrient (SN, SP, SK). In step 3, two yield estimates are obtained for each nutrient (YND, YNA, YPD, YPA, YKD, YKA) from the UN, UP and UK estimated in step 2. In order to, two experiments were conducted. The first one was a survey experiment in the 45 wheat production fields. The latter was an experiment based on completely randomized design with 36 fertilizer treatments. Before the experiments, soil samples were obtained from the farms and analysis were conducted to determine the nutrients. Grain and biological yields, NPK uptake, internal use efficiency and maximum nutrient accumulation and dilution were obtained from these two experiments. Results indicated that maximum and minimum internal use efficiency of N were 48 and 25 Kg/Kg in the first Experiment and 46 and 17 Kg/Kg in the second experiment. Maximum and minimum internal use efficiency of P changed from 194 to 442 Kg/Kg in the studying fields in the first experiment. The same results were 97 to 264 Kg/Kg in the second experiment. Results showed that maximum and minimum internal use efficiency of K ranged from 32 to 68 Kg/Kg in the first experiment. The same results for the second experiment were from 9 to 25 Kg/Kg. Maximum nutrient dilution for NPK were obtained 46, 415, and 56 (Kg grain/Kg nutrient uptake). Maximum nutrient accumulation for NPK were 14, 120, and 14 (Kg grain/Kg nutrient uptake). There was no report on maximum nutrient dilution and accumulation of NPK for a crop in Gorgan or Iran. The presented approach using QUEFTS allows not only the estimation of nutrient requirements to achieve a certain yield target, it also provides a useful tool for identifying nutritionally optimal yield targets. The calibration of the QUEFTS model for wheat required the estimation of the slopes of two borderlines describing the maximum accumulation (a) and dilution (d) of N, P and K in the plant in relation to grain yield.