Effect of nitrogen and zinc on the yield of submerged rice and uptake of N and Zn on unlimed and limed soils

Summary

The effect of N and Zn on the yield of submerged rice and uptake of N and Zn was studied on limed and unlimed soils in greenhouse. Nitrogen was applied at the rate of 0,80 and 160 ppm through urea, ammonium sulphate and ammonium nitrate, Zn at 0 and 10 ppm in limed (4% CaCO₃) and unlimed soils. Liming (4% CaCO₃) decreased dry matter yield of rice at tillering, heading and straw and grain at maturity significantly against unlimed treatments. Ammonium sulphate gave highest yield with all applied doses followed by ammonium nitrate and urea.

Zinc at 10 ppm increased dry matter and grain yield significantly over no Zn treatment in rice. The N sources gave N concentration and uptake in rice plants in decreasing order:

$$Ammonium sulphate > Ammonium nitrate > Urea.$$

The highest N concentration was recorded with 160 ppm followed by 80 ppm N through any source and lowest in control. The application of Zn increased and liming decreased N concentration and uptake by rice at all sampling stages. Highest N concentration (2.37 to 3.92%) was observed at tillering followed at heading (0.48 to 1.05%). At maturity N in grain ranged from 0.69 to 1.13% whereas in straw from 0.24 to 0.41%. There were positive significant interactions of N(S) x N(L), N(S) and N(L) x Zn and negative interaction with lime on yield, N concentration (%) and N uptake (mg/pot).

The application of N sources and levels and Zn increased Zn uptake (μg/pot), and liming decreased it. But 160 ppm N through any source decreased straw Zn concentration over 80 ppm N in absence of added Zn, however, effects on grain were not so strong particularly that of 160 ppm, when 10 ppm Zn was also added even 160 ppm N increased Zn concentration over 80 ppm significantly in both straw and grain. In this case the effect of N sources on Zn concentration was in the order:

$$Ammonium sulphate > Urea > Ammonium nitrate.$$