Effect of water management and soil salinity on the distribution of fertilizer (65)Zn in alkaline soils and uptake by rice

When fertilizer Zn is applied to rice (Oryza sativa L.) soils to alleviate its deficiency, it distributes into different chemical forms. The nature and magnitude of these Zn forms and their availability to rice depend on the physico-chemical properties of the soils. To evaluate the effects of different moisture regimes and salt levels on the distribution of fertilizer (65Zn in alkaline soils and uptake by rice, laboratory incubation and greenhouse studies were conducted. The Dewitt silt loam and the Perry silty clay were limed to pH 7.5 and four salt treatments (0 (untreated control), 1, 2, and 3 dS m-1) applied. Three moisture regimes were, (1) moist, (2) alternate wet-moist, and (3) flooding. Applied fertilizer 65Zn was mainly distributed into more plant available (watersoluble+exchangeable, organic) and intermediately soluble (Mn-oxide, amorphous Fe-oxide) fractions. Recovery of applied fertilizer in least soluble (crystalline Fe-oxide, residual) fraction was comparatively low. Native soil Zn, on the other hand, mainly existed in least soluble fractions. Different moisture regimes and salt levels produced significant effects on the distribution and then redistribution of Zn among soil fractions. These results indicate that application of fertilizer 65Zn could help in increasing the availability of Zn to plants in saline and alkaline soils.;Rice produced the highest dry matter under flooding and the lowest under alternate wet-moist conditions. Dry matter yield decreased with the increase in soil salinity at all moisture regimes. In the Dewitt silt loam, 65Zn concentration in rice plant tissue was highest under flooding at all salinity levels as compared to moist and wet-moist conditions. In the Perry silty clay, none of the salt treatments nor moisture regimes produced any significant effect on 65Zn concentration in rice plant tissue. In both soils, 65Zn uptake under all moisture regimes was highest at 0 dS m-1 and then decreased with the increase in soil salinity. Highest 65Zn uptake was observed under flooding as compared to other moisture regimes. Native soil Zn uptake was significantly higher from the Perry silty clay as compared to the Dewitt silt loam. Soil Zn uptake was highest under flooding and at 0 dS m -1 compared to other moisture and salt treatments. Total Zn uptake was significantly higher in both soils under flooding, however, greater total Zn uptake was observed on the Perry silty clay. Total Zn uptake decreased with the increase in soil salinity in both the Dewitt silt loam and the Perry silty clay. The decrease in Zn uptake with the increase in soil salinity was mainly the result of lower dry matter production with the increase in soil salinity. Recovery of fertilizer 65Zn by plants was ≤2%.