Applications in sustainable production

Abstract

Capsicum plants (Capsicum annuum L. cv. Lamuyo) were grown in controlled greenhouse conditions. The crop underwent fertirrigation with different levels of N and K, with a complement of other essential nutrients. The plants were sampled periodically to determine leaf levels of total and soluble K and Na. Both nutrients can be used for the diagnosis of physiologically active endogenous levels. Endogenous levels may or may not depend on the exogenous level. Soluble Na showed low levels in the N group with the lowest rhizospheric N levels, with a minimum when K concentrations in the growth medium were also low (T₂), while T₄ showed a higher leaf concentration although the presence of N and K in the rhizosphere was not significant. Total Na levels were more closely linked to doses applied, with the minimum leaf level occurring when the external concentration was lowest and the maximum when it was highest, although with the lowest K concentration. Soluble K was very closely related to external K levels, rather than to the amounts of N applied. The soluble K+soluble N and soluble K/soluble Na ratios confirmed the total dominance of univalent cations in treatments with high levels of K, regardless of how much N was applied. Soluble forms of the two cations showed the differences between treatments more clearly than the total forms, as did the ratios. This would suggest that the sum and its ratio provide a discriminatory system which enables the characteristics of the effect of fertilizer to be accurately determined, as individual study of both cations would not be possible. In the present study Na levels were not particularly high, in comparison with the K levels obtained.