Abstract
To investigate the effect of long-term lantana (Lantana camara L.) addition on changes in soil Zn fractions and rice and wheat yield grown in sequence, an experiment was started in 1988 with four levels of lantana (0, 10, 20, and 30 t ha-1 on fresh weight basis) and three tillage practices. The three tillage practices were subsequently replaced by three N and K levels to rice (33, 66, and 100% of recommended dose) in 1997, whereas P was not applied to rice. The following wheat crop received a basal dose of 66% of the recommended rate of N, P, and K. The soil analysis (0--0.15 m depth) after the harvest of wheat 2000-2001 indicated that 12 continuous additions of lantana from 10-30 t ha-1 resulted in an increase in non-specifically adsorbed exchangeable Zn (Zn1), specifically adsorbed exchangeable Zn (Zn2), and organically bound Zn (Zn3), a decrease in Fe and Al bound Zn (Zn5), and no effect on manganese oxide bound Zn (Zn4) and residual Zn (Zn6). Latana addition also increased DTPA (diethylenetriamine pentaacetic acid) extractable Zn in soils. Although all the Zn fractions except Zn6 revealed interdependency, strong associations were observed among the Zn1, Zn2, and Zn3 fractions. Individually, the addition of lantana and fertilizer increased rice and wheat yield significantly. At 20 and 30 t ha-1 lantana addition, there was a net savings of 33% N and Kin rice and 100% of P, whereas in the case of wheat, the saving was of the order of 33% N, P, and K. The first three Zn fractions, viz., non-specifically adsorbed exchangeable Zn (Zn1), specifically adsorbed exchangeable Zn (Zn2), and organically bound Zn (Zn3) were found to be the most important Zn fractions for the nutrition of rice and wheat grown in a sequence.
