Date of Award:

5-1997

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plants. Soils and Biometeorology

Committee Chair(s)

Daniel T. Drost (Committee Chair)

Committee

Daniel T. Drost

Abstract

Crops grown in sandy soils require frequent irrigation. As a result, nitrogen (N) fertilizers. such as ammonium sulfate((NH4)2SO4), are leached from the rooting zone of crops. This loss of N increases N fertilizer use and the potential for nitrate (NO3-) contamination of water. Ammonium-loaded clinoptilolite (NH4+-Cp) may reduce this N leaching, increase N fertilizer use-efficiency, and prevent NO3- contamination of water while sustaining normal crop growth.

The potential of NH4+-Cp as a N fertilizer was assessed in three leaching experiments without plants and two leaching experiments with plants. Pots containing rounded quartz sand were amended with (NH4)2SO4 and one of three NH4+-Cp size fractions: small (2SO4 and the rate of NHi + release is affected by size fraction . The large size fraction leached less N (as NH/ and NO3-) than the small or medium size fractions . The leaching experiment was then repeated twice in pots containing sandy soil. Results again indicated that NH/ -Cp leaches N much slower than (NH4)2SO4. No differences in N leaching were found among NH4+-Cp size fractions. However, after extracting the NHi4+ -Cp from the soil, the greatest concentration of N was recovered from the largest size fraction and the least concentration of N was recovered from the smallest size fraction.

Finally, in two leaching studies, pots containing the sandy soil were planted with sweet corn and grown for 35 d and 42 d, respectively. No differences were found among N sources in corn relative growth rates, leaf area ratios, and net assimilation rates, even though the corn plants that were fertilized with NH4+-Cp assimilated significantly more N than the (NH4)2SO4-fertilized plants. The pots fertilized with NH5+-Cp leached

In the greenhouse, NH4+-Cp is a slow-release fertilizer that will reduce N leaching while maintaining normal plant growth. However, field studies are needed to confirm the suitability of NH4+-Cp as a slow-release fertilizer under field conditions.

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