Department of Land Resources and Enviromental Sciences Thesis Defense

Andrew John, MS. Candidate in Land Rehabilitation, will present "The Effect of Agricultural Practices on Nitrate Leaching, Grain Yield and Quality, and Net Revenue in a Semiarid Region" as part of his thesis defense in 138 Animal Bioscience Building.

Abstract

Throughout the world, high nitrate concentrations in groundwater have been observed in agricultural regions. In the Judith River Watershed of central Montana, groundwater nitrate concentrations have increased from 10 to 25 mg L-1 over the span of 20 years. Nitrate leaching from agricultural fields is a major concern for growers and stakeholders in the region. Little research has been conducted in dryland semiarid regions on the effects of agricultural practices on nitrate leaching.

We conducted a 2-yr study comparing three alternative management practices (pea, controlled release urea, split application) to grower standard practices (fallow, conventional urea, spring broadcast urea) on grain yield, grain protein, net revenue, and the amount of nitrate leached. Eight field treatment interfaces were established across three farms and each treatment was analyzed in duplicate. Ten soil and biomass sampling locations were designated on both sides of the interface. Net revenue was calculated by enterprise budgets constructed from local and state data. Nitrate leaching was calculated using a nitrogen mass balance equation.

Replacing pea with fallow decreased both yield and protein of the subsequent wheat crop in each year of the study. A net revenue difference between these two treatments was not observed in 2013. However, in the second year (2014) wheat after pea earned $83 ha-1 more (P<0.1) than wheat after fallow. Neither fertilizer alternative management practice had an effect on net revenue. In the 2013 treatment year, wheat after pea leached less nitrate (20 kg N ha-1) than wheat after fallow (56 kg N ha-1). In the 2014 treatment year, a greater amount of nitrate leached (P<0.1) while using controlled release urea than conventional urea, possibly in part because the controlled release urea was applied earlier than conventional urea.

The results of our study revealed that replacing pea with fallow can decrease the amount of NO3- that leaches out of the root zone. Also, this practice either increased or had no effect on net revenue, revealing its ability to be economically feasible for a grower to implement. Based on our findings, future research should likely focus on practices that decrease rates of deep percolation.

• Google Calendar
• iCal