Carbon-nitrogen interaction related to P, K, Ca, and mg nutrients in field crops

Abstract

Carbon (dry matter)-nitrogen relationship was expressed as DMt = DM0 × exp(CNI × Nt) in Gramineae crops (including root crops), and DMt = DM0 + CNF × Nt in Leguminosae crops, where DMt is the amount of dry matter at various growth stages, Nt is the amount of nitrogen absorbed at various growth stages, DM0 is the initial value, and CNI and CNI′ are coefficients. Thus, since the carbon-nitrogen relationship was different between Gramineae and Leguminosae crops, it is expected that the accumulation processes of other minerals such as phosphorus (P), potassium (K), calcium (Ca), or magnesium (Mg) during growth would be different between Gramineae and Leguminosae crops if these nutrients are closely related to the carbon and nitrogen metabolism. As nitrogen is the most important nutrient for plant growth, the relationship between Nt and the amount of other minerals such as phosphorus (Pt), potassium (Kt), calcium (Cat), or magnesium (Mgt) absorbed in plants at various growth stages was examined in field crops. In Gramineae crops, the Pt-Nt, Kt-Nt, and Mgt-Nt relationships during growth were described as follows: where P0 and Mg0 are initial values, and PNI, KNI, Kmax, and MgNI are coefficients. Since the Pt-Nt and Kt-Nt relationships changed according to the growing conditions, the values of PNI and KNI were statistically estimated from the data of various growth stages at each treatment. As PNI showed a linear regression with CNI, Pt and also Kt was expressed by the equation which included CNI. Thus both phosphorus and potassium accumulation were closely related to the carbon-nitrogen interaction. While the Mgt-Nt relationship was less affected by various growing conditions, MgNI was estimated from the data including all treatments, indicating that Mg accumulation was regulated only by nitrogen nutrient. Cat was not related to Nt. In Leguminosae crops, the Pt-Nt, Kt-Nt, and Mgt-Nt relationships were described as follows: where P0 K0, and Mg0 are initial values, and PNI′ and KNI′ are coefficients. Since the Pt-Nt, Kt-Nt, and Mgt-Nt relationships were less affected by various growing conditions as in the case of DMt-Nt, the values of PNI′ and KNI′, and MgNI were estimated from the data including all treatments. Thus, P, K, and Mg accumulation was closely regulated by N nutrient. Cat was not related to Nt. Consequently, in Gramineae crops, P and K accumulation was assumed to be related to the carbon-nitrogen interaction, while in Leguminosae crops, P and K accumulation was assumed to be related to only nitrogen nutrient, indicating that the role of P and K nutrients differed according to differences in the balance of the carbon-nitrogen metabolism. Since MgNI was estimated from the same form of Mgt-Nt regression regardless of Gramineae and Leguminosae crops, Mg accumulation was assumed to be closely regulated by only nitrogen nutrient. Ca accumulation was neither related to N nutrient nor carbon-nitrogen interaction. © 1996 Taylor & Francis Group, LLC.