|Full text PDF:||http://hdl.handle.net/10415/1581|
Technological advancements, such as variable-rate technology (VRT), in agricultural application equipment have led to the belief that application accuracy of crop inputs have improved. However, minimal research has been conducted to thoroughly validate this assumption; especially for organic fertilizers such as poultry litter which is inherently variable making it difficult to uniformly apply. Therefore, research was conducted to characterize and compare poultry litter mass and nutrient distribution patterns for a closed-loop system (CLS; spinner-disc control) and an open-loop system (OLS) determining: 1) whether spinner disc-control improves the distribution of litter, 2) the association of nutrient and mass patterns, and 3) if spread variability exists along the direction of travel. A typical litter spreader equipped with an electronically adjustable hydraulic flow control (proportional) valve was used to test the CLS and compare these results to the OLS, using a manual valve. Three application rates of 2242, 4483, 6725 kg/ha were selected for applying broiler litter using a two-dimensional pan matrix to assess spread distribution. The results indicated that the CLS was able to maintain more consistent spinner-disc speeds thereby producing less variable distribution patterns over the rates tested. The CLS also produced smaller coefficients of variation, 22% to 34%, for the majority of the mass and nutrient treatments improving spread uniformity by up to 17% over the OLS. Mass (p = 0.0524) and nutrient (p = 0.0657) pattern comparisons revealed that overall differences existed between the two systems. The nutrient patterns were highly correlated (r > 0.98) with their respective mass patterns indicating that even though particle size variability exists across the width of spread, the distribution of mass reflects nutrient distribution. The longitudinal results determined that variability along the direction of travel does exist when litter is applied; however, it was considered random. Overall, the CLS is recommended over the OLS especially if variable-rate application (VRA) is utilized or if application rates are changed frequently.