Soil and plant carbon, nitrogen, and phosphorus content and their stoichiometry in spring wheat under different irrigation treatments in the Loess Plateau

To investigate the change law of nutrients in soil-crop ecosystems, ripe Triticum aestivum located in the loess semi-arid region of Longdong, soil at a depth of 0 – 40 cm, and four different irrigation treatments W₅₀ (50 mm), W₁₀₀ (100 mm), W₁₅₀ (150 mm), and W₂₀₀ (200 mm) , were selected to analyze the nutrient and ecological stoichiometric characteristics of soil and leaves. The results showed that 1) the content of soil organic carbon and total nitrogen first increased and then decreased as the amount of irrigation increased, and the total phosphorus content did not change much with increased irrigation; organic carbon and total nitrogen content in the 0 – 40 cm soil layer decreased as soil depth increased, and the total phosphorus content did not change significantly as soil depth increased. 2) The content of C, N, and P in T. aestivum first increased and then decreased as amount of irrigation increased. When the irrigation amount was 150 mm, the maximum value was reached; the ratios of leaf C∶N, C∶P, and N∶P first decreased and then increased. According to the N∶P < 14 observed in the T. aestivum leaf, the growth of T. aestivum in Longdong was limited mainly by N. 3) There was a significant correlation between soil and leaf nutrient transformation in T. aestivum, and C∶P was the most sensitive to the nutrient relationship. The results showed that nitrogen fertilizer should be increased to ensure higher and more stable yield of T. aestivum when the irrigation amount is 150 mm.