Precision manure management on site-specific management zones: Nitrogen mineralization

ABSTRACT

Precise quantification of nitrogen (N) mineralization in animal manure from different productivity-level management zones (MZs) could result in efficient and safe utilization of manure as N fertilizer. The objective of this study was to compare N mineralization rates of dairy cattle manure within and across three productivity-level MZs. To accomplish this, a 120 day laboratory incubation study was conducted at the Natural Resources Ecology Laboratory at Colorado State University using a completely randomized design set as a 2 factor factorial. Treatments for the study, which included the field equivalent of, 22, 44, 67, and 134 Mg ha⁻¹ of applied animal manure, were replicated four times. Soils used in the study were collected from the top 15 cm of high, medium and low MZs from Fort Collins, Colorado, USA on a continuous corn (Zea mays L.) field. A significant difference (P ≤ 0.05) in mineralized N across MZs was found across manure rates. The high, medium and low MZ N mineralization rates were compared and there was no significant difference in cumulative N mineralized between MZs over time. The lack of statistical difference in mineralized N between MZs is hypothesized to have been influenced by the lack of substantial difference in soil pH and particle sizes (only 6% clay difference between MZs). That being the case, a study involving spatially variable soils with significantly different soil particle size between MZs may result in a different conclusion. The results of the study support the hypothesis that variable rates of manure mineralize differently within MZs; however, the results do not support the hypothesis that variable rates of manure in soil may mineralize differently across MZs.

KEYWORDS:

• manure management
• nitrogen mineralization
• site-specific management zones