The Effect of Nitrogen and Types of Nitrogen Carrier on Plant Uptake of Indigenous and Applied Zinc

Abstract

Abstract Zinc uptake from Ritzville fine sandy loam in pots was measured by successive cropping with two crops of milo, four cuttings of Ladino clover and a final crop of milo. The zinc treatments consisted of 4 pounds zinc (as sulfate) per acre applied initially, and none. The 4 nitrogen treatments in factorial combination with the zinc treatments applied to each of the first 2 crops of milo were none, and 200 pounds nitrogen per acre as (NH 4 ) 2 SO 4 , NH 4 NO 3 , and NaNO 3 , respectively. No nitrogen was applied to the clover; 200 pounds nitrogen per acre were applied uniformly to all treatments during the growth of the final milo crop. Significant yield increases due to zinc application were obtained on the second and third crops of milo and the first cutting of clover when NaNO 3 was used as a nitrogen source. A range in soil pH from 5 to 7.3 resulted depending on the nitrogen source. Zinc uptake by all crops was increased by the initial zinc application. Nitrogen application generally increased the uptake of both native and applied zinc, the effect depending on the change in pH brought about by the nitrogen carrier. NaNO 3 tended to decrease uptake of native zinc except on the first two crops of milo. Uptake of indigenous zinc where the soil pH had been lowered to 5 by use of (NH 4 ) 2 SO 4 was equal to that obtained with 4 pounds of ZnSO 4 when the soil pH was raised to 7.3 using NaNO 3 . Multiple regression analysis of the Zn uptake data indicated that the diverse effects of nitrogen sources could be explained by shifts in soil pH and by differences in plant growth. Only a small portion of the applied zinc was utilized by any one crop, and the utilization changed little with cropping. Zinc applied as sulfate remained available during the cropping sequence.