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Forages

Nutritive Value and Nutrient Uptake of Sorghum–Sudangrass under Different Broiler Litter Fertility Programs

Department of Agriculture, Western Kentucky Univ., 1906 College Heights Blvd. #41066, Bowling Green, KY 42101-1066

^* Corresponding author (sleugh2{at}msn.com)

Received for publication October 14, 2005.

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY AND CONCLUSIONS REFERENCES

 
Broiler (Gallus gallus) litter fertility regimes and nutrient removal by sorghum–sudangrass [Sorghum bicolor (L.) Moench] are not well defined. The objective of this study was to determine broiler litter fertility regimes for sorghum–sudangrass that would maximize nutrient removal and produce comparable forage nutritive value compared with inorganic fertilizers while reducing potential soil nutrient accumulation. A randomized, complete-block experiment with four replications and four treatments (litter applied at recommended nitrogen [N] rate [Litter-N], recommended phosphorus [P] rate plus supplemental inorganic N [Litter-P+N], recommended P rate [Litter-P], and inorganic fertilizer [INORG]) was established. Acid detergent fiber (ADF), neutral detergent fiber (NDF), crude protein (CP), P, Cu, Fe, and Zn were determined. Treatments did not affect ADF, NDF, Cu, or Fe in 2001, whereas ADF and NDF were similar for INORG and Litter-N in 2002. Greatest P concentrations were observed in Litter-N and Litter-P plots. Crude protein was greatest for INORG plots, similar for Litter-P+N and Litter-N treatments, and lowest for Litter-P plots. Treatments affected Cu and Zn: Forage from Litter-N plots contained 44% greater forage Cu than those from Litter-P plots in 2003. Iron concentration for 2003 was 60% higher than for 2001 in Litter-N plots, and there were 22% and 30% increases in P uptake in 2003 compared with 2001 for the Litter-N and Litter-P+N plots, respectively. Lower rates of broiler litter, applied based on the P requirement and supplemented with inorganic N, can produce similar forage nutritive value to that fertilized with inorganic fertilizer only or broiler litter applied to meet crop N requirements.

Abbreviations: ADF, acid detergent fiber • CP, crude protein • INORG, inorganic fertilizer • NDF, neutral detergent fiber

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY AND CONCLUSIONS REFERENCES

 
BROILER (Gallus gallus) production has increased 10-fold in Kentucky over the last 8 yr (KASS, 2003) and continues to increase in the southeast USA. The expansion of the poultry industry and an increase in the price of inorganic fertilizer, especially nitrogen, has led to an increase in the use of broiler litter (a mixture of chicken manure, wasted feed, wood shavings or crop residue such as rice or peanut hulls, and feathers) as a source of crop nutrients. This increase in poultry production has led to an increase in broiler litter and the associated problem of how to handle, use, or dispose of it in an environmentally sustainable manner. Broiler litter is often over applied to fields in close proximity to poultry production areas in an effort to dispose of the litter. This practice may cause water pollution and soil nutrient imbalances. Long-term application of broiler litter to soils can lead to an accumulation of soil nutrients including phosphorus (P), potassium (K), copper (Cu), and zinc (Zn) (Kingery et al., 1993; Sistani et al., 2004b) and can have adverse environmental impacts (Kingery et al., 1994). Even with these risks, Kingery et al. (1994) concluded that land application remains the most practical way to manage large quantities of broiler litter.

Studies have shown that with good management, broiler litter can be a valuable source of nutrients for crops such as bermudagrass [Cynodon dactylon (L.) Pers.] (Torbert et al., 1992; Evers, 2002; Sistani et al., 2004b), many cool season forage grasses and legumes (Braden and West, 2000; Pederson and Brink, 2000; Brink et al., 2001; Pederson et al., 2002; Sleugh et al., 2004), cotton (Gossypium hirsutum L.) (Sistani et al., 2004a) and sorghum–sudangrass (Embrey et al., 2003). Differences exist in nutrient uptake of cool-season versus warm-season forages and grasses versus legumes (Brink et al., 2001; Sleugh et al., 2002). Aboveground plant parts (stems and leaves) usually contain most of the N, P, K, Zn, and Cu (Pederson and Brink, 2000; Pederson et al., 2002). Therefore, crops receiving nutrients from broiler litter can be harvested as hay or silage in an effort to export the nutrients from the site where they were applied. Forage crops remove a relatively small quantity of many nutrients relative to the amounts of those nutrients applied, but hay production is an important component of nutrient management (Brink et al., 2002).

It is important that litter application rates be tailored to meet crop requirements and/or their uptake potential. Broiler litter as a source of N has been used to produce forage with yield and nutritive value that is equal to or better than forage fertilized with ammonium nitrate (Torbert et al., 1992). Generally, broiler litter is slightly greater in N than P. However, forage crop requirement for N is considerably greater than the requirement for P. Because of this difference in the concentration of the various nutrients contained within broiler litter, one nutrient (e.g., N) may be undersupplied while another (e.g., P) is oversupplied, thus creating a potential pollution problem. This situation has caused some states to require that animal wastes be applied based on crop P requirement. Producers typically apply broiler litter based on one of three criteria: N requirement of the crop, a fixed tonnage per acre, or until all the broiler litter is disposed of. Each of these criteria could lead to major differences in forage yield and nutritive value and to excessive accumulation of certain soil nutrients. Unless continuous soil test monitoring is done, broiler litter is applied at the proper rate, and crop nutrient removal is maximized, P, Cu, and Zn may accumulate in soils receiving long-term application of broiler litter (Sistani et al., 2004b). Sorghum–sudangrass is becoming much more popular with cattle producers in Kentucky, and it is considered to be an ideal crop for poultry litter application because of its response to N fertility and its high biomass yield.

Many studies (Harvey et al., 1996; Brink et al., 2001; Adeli and Varco, 2001; Evers, 2002; McLaughlin et al., 2004; Adeli et al., 2005) address the use of poultry litter, swine effluent, or dairy slurry as a nutrient source for crops, but these materials are usually applied based on the N requirement of the crop or on flat or comparative rates. Sorghum–sudangrass has been found to be a good alternative for nutrient management hay systems in the southeastern USA (McLaughlin et al., 2004). Therefore, fertility regimes for sorghum–sudangrass, which include broiler litter, that can produce similar forage yield and nutritive value to inorganic fertilizer while reducing nutrient loading need to be investigated. Additionally, litter application and nutrient removal rates for sorghum–sudangrass are not well defined. The objective of this study was to determine broiler litter fertility regimes for sorghum–sudangrass that would maximize nutrient removal and produce comparable forage nutritive value compared with inorganic fertilizers while reducing potential soil nutrient accumulation.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY AND CONCLUSIONS REFERENCES

 
Sorghum–sudangrass plots (8 by 100 m) were established in 2001, 2002, and 2003 at Western Kentucky University's Agricultural Research and Education Complex in Bowling Green, Kentucky on a Pembroke silt loam (Mollic Paleudalf) with a pH of 5.1. Twenty to 25 soil samples (15-cm depth) were taken before planting to determine fertility needs for each plot. Soil chemical characteristics at the beginning of each season and at the end of the study are presented in Table 1. The amount of nutrients applied (to meet crop N or P need) was based on the soil chemical characteristics for each plot (Table 1) and a specified yield goal. On plots where broiler litter was applied to meet crop N, the amount of litter applied was based on litter N content and the estimated amount of N that would be available. Soil N was not used to determine N fertilization rates because soil organic matter and nitrate content have not proven to be reliable indicators of available N for field crops grown under Kentucky conditions (Thom et al., 2000). Phosphorus application rates were also based on crop P need and were modified based on soil P content and the estimated amount of P that would be available from the litter to be applied. Analysis of broiler litter used and application rates are presented in Tables 2 and 3, respectively. Broiler litter mineralization rate was assumed to be 50% for N and 80% for P. Treatments were applied to the same plots for each year of the experiment, and this led to some difference in fertilizer recommendations for each treatment in subsequent years. Plots were disked twice, fertility treatments were applied and incorporated with a spring tine harrow, and plots were cultipacked before planting. Mean monthly temperatures and precipitation rates for the growing season (April–October) are shown in Fig. 1 and 2 , respectively.

View this table: [in this window] [in a new window]   Table 3. Amount of nutrients from broiler litter and inorganic fertilizer applied to sorghum–sudangrass in 2001, 2002, and 2003.

View larger version (25K): [in this window] [in a new window]   Fig. 1. Monthly and 30-yr average temperature for the growing season (April–October) in 2001, 2002, and 2003.

View larger version (24K): [in this window] [in a new window]   Fig. 2. Monthly and 30-yr average precipitation for the growing season (April–October) in 2001, 2002, and 2003.

Plots were harvested at the boot to early heading stage three times in 2001, twice in 2002, and three times in 2003. An area 3 by 0.8 m in each plot was harvested by clipping at a 5-cm height, and forage weight was used to determine yield. Grab samples were collected randomly throughout the rest of the plot by clipping, chopping, and combining approximately 15 plants to form a composite sample for that plot. Composite samples were weighed, dried in a forced-air dryer at 60°C for 48 h, weighed again, and ground to pass through a 1-mm screen. These samples were used to determine nutrient concentration and dry matter percentage for yield calculation.

A set of 40 calibration samples were selected (Shenk and Westerhaus, 1991) and used to determine crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), P, Cu, Zn, and Fe concentration. Crude protein was determined using a Leco-528 nitrogen combustion analyzer (Leco Corp., St. Joseph, MI). Acid detergent fiber (Association of Official Analytical Chemists, 2000a, 2000b [method 973.18]) and NDF (Goering and Van Soest, 1970) were determined. Minerals such as P, Cu, Zn, and Fe were measured using a PerkinElmer 3300 XL ICP (Shelton, CT). The other samples were predicted using near-infrared reflectance spectroscopy (Windham et al., 1989). Reflectance measurements (log 1/R) were collected for all samples from 1100 to 2500 nm and recorded at 4-nm intervals by using a Foss 6400 scanning monochromator (Foss North America, Eden Prairie, MN). Nutrient uptake was calculated as the product of forage dry matter yield and nutrient concentration of P, Cu, Zn, and Fe for each plot and summed over the harvests to reflect total nutrient uptake for the season.

Statistical analysis was performed with the General Linear Model procedure of SAS (SAS Institute, 1991). Mean comparisons were made with an F-protected LSD (Steele and Torrie, 1980) at P 0.05 unless otherwise noted.

	RESULTS AND DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY AND CONCLUSIONS REFERENCES

 
Acid Detergent Fiber, Neutral Detergent Fiber, and Crude Protein
There was a treatment x year interaction for ADF, NDF, CP, and nutrient concentration; therefore, the data for each year are presented separately. In 2001, treatment had no effect on ADF and NDF (Table 4). This may have been due to the less than normal precipitation (Fig. 2). Similar ADF and NDF concentrations were observed for INORG plots and the Litter-N treatments in 2002. In 2003, all treatments except Litter-P had similar NDF, whereas Litter-P+N, Litter-N, and INORG were similar in ADF concentration. These data for 2001 and 2003 are similar to data reported by Harvey et al. (1996) in that the NDF and ADF levels in bermudagrass were not affected by the level of N. Data from this research differed from data reported by Adeli et al. (2005) in that ADF and NDF concentrations were positively correlated with temperature increases during the growing season even though mean temperatures during the 2001 and 2002 growing season were slightly greater than the 30-yr average (Fig. 1).

In 2002, Litter-N and INORG treatments had similar CP, suggesting, as reported by Adeli et al. (2005), that the litter and INORG had similar N availability. Litter-N plots had the greatest CP in 2003. Litter-P+N and INORG were similar, and Litter-P was lowest. The low CP concentration in Litter-P plots may have been because of the low amount of N applied. Lower rates of broiler litter, applied to meet crop P requirement and supplemented with inorganic N (Litter-P+N), produced forage with similar CP concentration to INORG in 2002 and 2003.

Mineral Concentration (Phosphorus, Copper, Iron, and Zinc)
There were few differences in P concentration among treatments in 2002 and 2003 (Table 5). In 2001 and 2002, greater P concentrations were observed in Litter-N, Litter-P, and Litter-P+N. This may have occurred because available N in the Litter-N plots boosted yield (Table 6), which typically leads to increased nutrient concentration (Adeli and Varco, 2001; Robinson, 1996). In contrast to the data observed in this research, Evers (2002) suggested a dilution effect on P concentration by the increase in forage production caused by increased N. The Litter-P+N plots forage P concentration was enhanced by the availability of N from the supplemental inorganic N that was applied. This finding agrees with the conclusion of Adeli and Varco (2001) that for grasses to be used in nutrient management plans, high rates of N are needed. Additionally, due to the limited N that was available in the Litter-P plots, crop growth and yield was limited. This limited growth/yield may have led to a high concentration of P (Evers, 2002) in the Litter-P plots. Concentration of P was similar for all treatments except Litter-P (which was the greatest) in 2003. Averaged over treatments, P concentrations in this research are nearly twice that reported by McLaughlin et al. (2004). Results from this research indicate that Litter-P+N was similar to INORG in P concentration in two of three years (2002 and 2003). Even though average total yield was similar for Litter-N and Inorganic plots, the concentration of P, Cu, Fe, and Zn were greatly elevated in the Litter-N plots. Soil Zn, Cu, and P concentrations in Litter-N plots were nearly twice of the INORG plots at the end of the study. There was no difference in soil P, Cu, Fe, and Zn accumulation in the Litter-P, Litter-P+N, and INORG plots. The forage concentration of P observed in this study was consistently greater than that reported by Brink et al. (2001) for oat (Avena sativa L.), wheat (Triticum aestivum L.), rye (Secale cereale L.), and several legumes.

View this table: [in this window] [in a new window]   Table 6. Forage yield of sorghum–sudangrass with varying broiler litter and inorganic fertilizer regimes in 2001, 2002, and 2003.

There was no difference in Fe concentration among treatments in 2001 and 2002 (Table 5). In 2003, the greatest concentration was seen in the Litter-N plots, and the lowest was seen in the Litter-P plots. Inorganic fertilizer and Litter-P+N treatments were similar. Even though Fe content of the broiler litter was lowest in 2003 (Table 2), it may have taken 2 yr to build up enough soil Fe to affect forage uptake. Elevated forage Fe and Cu concentration could cause toxicity problems for livestock (Kingery et al., 1993). With the exception of forage Zn (2001) and Cu (2003) concentration in the Litter-P plots (Table 5), all other forage mineral concentrations were higher than the minimum requirements for beef cattle but less than the maximum tolerable level (National Research Council, 2000).

Mineral Uptake (Phosphorus, Copper, Iron, and Zinc)
Nutrient uptake of P, Cu, Fe, and Zn is presented in Table 7. The data represent total nutrient uptake for the growing season. In 2001, except for Fe, uptake of other nutrients in the Litter-P+N plots was 50 to 100% greater than that of Litter-P plots. Greater nutrient uptake was observed in the INORG plots and Litter-N plots in 2001 and Litter-P plots consistently had the lowest nutrient uptake in 2001 and 2003. The lower uptake in the Litter-P plot is associated with the lower forage yield (Table 6) and affects mineral concentration and removal (Adeli and Varco, 2001). This is a clear indication that when broiler litter is applied to meet the crop's N requirements, P is over supplied and taken up by the crop. In two of the three years (2001 and 2003), P concentration was greater in the Litter-N plots that in the Litter-P+N plots. There were 29 and 43% increases in P uptake in 2003 compared with 2001 for the Litter-N and Litter-P+N plots, respectively. In 2001 and 2002, Cu uptake was similar in the Litter-N and inorganic plots, whereas the Litter-N plots had the greatest uptake in 2003. Copper uptake was lowest in the Litter-P plots in 2001 and 2003, with all other treatments having more than twice the level of uptake. Litter-N, Litter-P+N, and Litter-P had similar nutrient uptake in 2002, and the greatest uptake was observed in the INORG plots. These uptake levels were lower than those reported by McLaughlin et al. (2004).

The INORG, Litter-N, and Litter-P+N plots had similar uptake of Fe in 2001 and 2002, whereas INORG and Litter-P+N were similar in 2003. Over the 3 yr, the difference in Fe uptake varied from 50% (Litter-P) to 66% (INORG) from 2001 to 2003. The highest uptake (INORG, 2003) was still lower than that reported by McLaughlin et al. (2004).

The differences in the mineral uptake of the treatments are reflected in the nutrient accumulation in the soil at the end of the experiment in 2003 (Table 1). Litter-N plots had 54, 54, and 72% more P, Cu, and Zn, respectively, than Litter-P plots did.

	SUMMARY AND CONCLUSIONS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY AND CONCLUSIONS REFERENCES

 
After 3 yr of broiler litter application, soil P, Cu, and Zn were 100 to 300% greater than they were before the application of litter at high rates. Plots receiving litter at high rates had greater soil accumulation of P, Cu, and Zn, compared with plots receiving litter at lower rates and then supplemented with inorganic N. Forage P, Cu, Zn, and Fe were higher than the minimum requirements for beef cattle but less than the maximum tolerable level established by the National Research Council. There was little or no difference in ADF and NDF for plots receiving inorganic fertilizer only compared with those receiving broiler litter to meet P needs and then supplemented with inorganic N. Plots receiving high rates of litter averaged 25% more CP in two of the three years. These results show that lower rates of broiler litter, applied based on the P requirement of the crop and supplemented with inorganic N, can produce forage with similar nutritive value to that fertilized with inorganic fertilizer only or broiler litter applied to meet crop N requirements. These reduced litter fertility programs can reduce soil nutrient accumulation by 50% and can lead to at least equal and sometimes better uptake of P, Cu, Fe, and Zn by sorghum–sudangrass compared with using inorganic fertilizer alone or applying litter to meet crop N requirements. Producers growing sorghum–sudangrass need to apply less broiler litter if they apply based on crop P requirements and therefore reduce the likelihood of soil accumulation of nutrients such as P, Cu, Fe, and Zn.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY AND CONCLUSIONS REFERENCES

 
This project was funded by a grant from the USDA-ARS as a part of National Program 206.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY AND CONCLUSIONS REFERENCES

 

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This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Sleugh, B. B. Articles by Henderson, H. D. Search for Related Content PubMed Articles by Sleugh, B. B. Articles by Henderson, H. D. Agricola Articles by Sleugh, B. B. Articles by Henderson, H. D. Related Collections Forage Management Nutrient Management