1. RESULTS AND DISCUSSION
Nutrient Accumulation in Sorghum-Sudangrass with a Winter Rye Cover Crop after Poultry Litter Application
Naomi S. Rowland, R.A. Gilfillen, B. Sleugh, W.T. Willian, M.L. Futrell Western Kentucky University, Bowling Green, KY
RESULTS AND DISCUSSION
Applying litter at PL-P rate led to lower Cu concentrations in sorghum-sudangrass (p<0.01) (Fig.2). Sorghum-sudangrass fertilized with litter at PL-N rate resulted in the highest concentration of Cu. In general, rye takes up less Cu than sorghum-sudangrass.
Sorghum-sudangrass fertilized with litter at PL-N rate had the lowest concentration of P (p<0.01) (Fig.3). This may be due to decreased P availability in litter. Generally, rye takes up more P than sorghum-sudangrass and over the past 3 years, the cover crop has resulted in decreased P accumulation (data not shown).
In rye, Zn was the only nutrient significantly affected by fertility treatment (Fig.4). Litter applied at PL-N rate resulted in significantly more Zn accumulation than litter applied at PL-P rate (p<0.05). This correlates with the lower Zn concentrations observed in sorghum-sudangrass that had a rye cover crop than sorghum-sudangrass alone.
Fertility treatment did not affect rye yield (Fig.5). Litter applied at PL-N rate resulted in highest yields of sorghum-sudangrass while litter applied at PL-P rate resulted in lowest yields (p<0.01). This is likely due to lower nutrient concentrations, since nutrient uptake is related to biomass (Evers, 2002).
Generally, Cu and Zn concentration tended to be lower in plots receiving litter at PL-P rate. However, these plots did not have sufficient N to stimulate good vegetative growth (Fig.1).
Applying lower rates of litter and supplementing with inorganic N (PL-P+N) generally produced forage of similar quality to forage receiving litter at PL-N rate (data not shown), although yields were not as high. This may still be an alternative management practice leading to lower soil nutrient accumulation while providing adequate forage quality for livestock.
LITERATURE CITED
Evers, G. W Ryegrass-bermudagrass production and nutrient uptake when combing nitrogen fertilizer with broiler litter. Agron. J. 94:
Kingery, W.L., C.W. Wood, D.P. Delaney, J.C. Williams, and G.L. Mullins Impact of long-term land application of broiler litter on environmentally related soil properties. J. Environ. Qual. 23:
Pederson, G.A. and G.E. Brink Maximizing nutrient uptake by forages. Proc. American Forage and Grassland Council. Madison, WI. July 16-19, 2000.
INTRODUCTION
Poultry production in Kentucky has increased greatly over the last decade and has led to an increase in poultry litter and the associated problems. Increases in the cost of nitrogen fertilizer has led many farmers to seek an alternate nutrient source for their crops. However, frequent or long-term application of litter can cause soil accumulation of nutrients (Kingery et al. 1994).
Plant stems and runners can take up as much as 50% of the applied N, P, K, Zn, and Cu. Harvesting of hay can thus result in a net export of nutrients from the field where they were applied (Pederson and Brink, 2000).
Many farmers apply litter to meet the N need of plants and therefore over apply P. Litter management strategies are needed that will optimize yield without jeopardizing the environment.
Our objective was to evaluate nutrient uptake of sorghum-sudangrass alone and with a rye cover crop to determine its viability as a nutrient removal tool.
MATERIALS AND METHODS
Sorghum-sudangrass was established into 7.6m × 45.7m plots in a conventionally tilled seedbed with a pH of 5.5 at the Western Kentucky University Agricultural Research and Education Complex in Bowling Green, Kentucky on a Pembroke silt loam (Mollic Paleudalf). After frost killed the sorghum-sudangrass, rye was established in half the plots as a winter cover crop.
Forage samples were collected prior to each harvest to determine dry matter yield and nutrient content. Three harvests were obtained in 2005, 2006 and Soil samples (15cm depth) were taken before litter application and the day of each harvest.
Four fertility treatments were used : (i) poultry litter applied at the recommended nitrogen rate (PL-N); (ii) poultry litter applied at the recommended phosphorus rate (PL-P); (iii) poultry litter applied at the recommended phosphorus rate with supplemental inorganic nitrogen (PL-P+N); (iv) recommended inorganic fertilizer (Inorg).
Data was analyzed by the GLM procedure of SAS (SAS Institute, 1998). Mean comparisons were made using an F-protected LSD.
Figure 1. Sorghum-sudangrass fertilized with poultry litter at the recommended P rate, supplemented with inorganic N (left) and P rate (right). a
p< 0.01
ACKNOWLEDGMENTS
This research was funded by a grant from the USDA-ARS.