Broiler Litter As A Source of N For Cotton

AGRONOMY SERIES
TIMELY INFORMATION
Agriculture & Natural Resources
Department of Agronomy & Soils, Auburn University, AL 36849-5533

Charles Mitchell
Extension Agronomist-Soils & Professor

Broiler litter has been successfully used on grass crops where precise nitrogen (N) fertilization is not necessary for optimum production. However, managing N fertility for cotton is critical to achieving maximum lint yields without risk of excessive vegetative growth from high soil N. Maximizing N use by crops is also important to minimize the environmental risks of excessive N application to agricultural lands.

More than 195,000 acres of cotton are produced in the northern third of Alabama where the poultry industry is also concentrated. In the Tennessee Valley, cotton is the major consumer of fertilizer N. Cotton acreage is also increasing in South Alabama and South Georgia where broiler production is increasing. This situation creates a potential for use of boiler litter as a source of N (and other nutrients) for cotton. This could lower the cost of production for cotton producers and lower the environmental risks where broiler litter disposal rates have traditionally been applied to Appalachian Plateau soils.

On-farm tests/demonstrations in North Alabama and research at the Tennessee Valley Substation (TVS) in northern Alabama on a Decatur silty clay loam and at E. V. Smith (EVS) Research Center in Central Alabama on a Norfolk fine sandy loam since 1990 have demonstrated the practicality of using broiler litter as a source of N for cotton. (See Table 1.).

Broiler Litter Composition

Fresh broiler litter averages about a 3-3-2 fertilizer, i.e. about 60-60-40 pounds N-P₂O₅-K₂O per ton. Most litter is used for its N value. When this is done, adequate P and K are usually applied for most situations except for soils testing very low in P and/or K. Nitrogen is the difficult nutrient to manage. Traditional reasoning is that not all of the nitrogen (N) in broiler litter is plant available since considerable N is tied up as organic compounds and some of the inorganic N (as ammonia) is lost when surface applied. Therefore, when using broiler litter for its N content, we generally assume about 2/3 of the total N will be plant available the year it is applied (Ala. Coop. Ext. Cir. ANR-244). Research suggests this is a very liberal approach to N fertilization but not unreasonable.

Rates Needed for Cotton

Surprisingly, most of the Alabama research has shown that pound for pound, the TOTAL N in broiler litter is only slightly less effective as the N in ammonium nitrate fertilizer (Fig. 1,2). A standard N recommendation for non-irrigated, Alabama cotton is 90 pounds total N per acre per year. Recommendations are that this be increased or decreased 30 pounds depending upon the soil, yield potential, and previous experience. Therefore, 2 tons per acre of average broiler litter (3-3-2 fertilizer) will provide 120 pounds total N, 120 pounds total P₂O₅, and 80 pounds total K₂O. If only 2/3 of the total N is actually available, this leaves 80 pounds N per acre which is within the standard recommendation.

Fig. 1. Average cotton lint yields from 3-yr research at the Tennessee Valley

Substation (North Alabama) and 4-yr at E.V. Smith Research Center (Central

Alabama). Note that broiler litter was almost as effective as a source of N for

cotton as ammonium nitrate fertilizer.

Fig. 2. Average yields of two, replicated on-farm tests with broiler litter and cotton

in North Alabama in 1990 (from Mitchell et al., 1992).

Time of Application

Split N applications are recommended for cotton in Alabama with most of the N applied prior to early bloom. Nevertheless, many growers, especially in North Alabama, apply all of the N at planting. In the Alabama research reported here, all of the broiler litter was applied at planting and lightly incorporated, usually with a field cultivator just prior to planting. This is both practical and economical. Applying broiler litter more than 1 month prior to planting is very risky. Spring rains could result in much of the readily available N leaching or denitrifying in Alabama soils.

Excessive Vegetative Growth

One would expect that over applying broiler litter would lead to excessive vegetative growth, late maturity, boll rot, and poor yields. RESEARCH DID NOT INDICATE THIS. Nitrogen rates as high as 240 pounds N per acre applied as broiler litter (approximately 4 tons per acre per year) did not reduce yields ( Fig. 1,2). High rates of broiler litter resulted in greener plants and slightly later maturity, but did not reduce yields. Pix® (mepiquot chloride) was applied to a duplicate set of broiler litter and fertilizer treatments. In 1992 at the TVS location (1 out of 7 site years), Pix resulted in significantly higher yield over all treatments but the yield increase from Pix was not due to broiler litter or N rates. In general, broiler litter at N rates up to 240 pounds N per acre did not decrease yields, and Pix was unnecessary to control excessive growth.

Nitrogen Carryover and the Residual Effects

There is a residual effect or carryover of N from one year to the next where broiler litter is applied, but from a practical standpoint, the effect on cotton is minimal. Some growers may have experienced problems with excessive N carryover, but this usually is a result of gross over application of litter, sometimes in excess of 10 tons per acre. Some researchers have suggested that around 5% of the total N applied may be carried over to next year's crop. This is reasonable from observations with cotton and corn in Alabama. High rates of broiler litter would slightly increase soil organic matter and thus the reserve of N in the soil. But this reserve cannot be depended upon to reduce next year's N application. It is also difficult to detect with soil inorganic N analyses.

Yield Enhancement

Yield enhancement from the use of broiler litter appears to be related mainly to the N applied (See Table 1.). Although there is generally thought to be some yield enhancement related to the benefits of additional organic matter in the soil - increased moisture retention, improved water infiltration (less runoff), improved soil structure, and better root growth. Higher soil organic matter has been associated with higher cotton yields in Alabama's Old Rotation experiment. Organic amendments have also been shown to reduce the harmful effects of plant parasitic nematodes.

Negative Effects

These and other experiments in Alabama have shown absolutely NO NEGATIVE EFFECTS of using broiler litter on cotton when the litter is applied primarily based on its N content and the N recommended for the crop. Some potential, long-term effects that are often mentioned include the following:

Nitrate leaching to groundwater. This could occur if greater than 3-4 tons per acre per year are applied to the same site for many years, and a shallow water table exists under permeable soils. This is an unlikely scenario in Alabama cotton fields.
Phosphorus buildup to excessive levels. Phosphorus (P) will buildup in the soil. Excessive P won't affect cotton growth or yield, but it could be an environmental problem in nonpoint source water pollution. Again, this is likely to be a problem primarily with annual, long-term P applications. Soil testing can avoid this situation. Good soil management can prevent P runoff from cropland (Mullins and Hajek, 1997).
Heavy metal buildup. Broiler litter may contain high levels of zinc (Zn) and copper (Cu), and these metals do build up in the soil. However, one ton of litter may contain only 1 pound of Zn and/or Cu. Often 3 pounds Zn per acre are recommended for corn. Therefore, excessive Zn and/or Cu is not likely to be a problem where broiler litter is used for its N value on cotton. Soil tests can identify fields where Zn and Cu have built up to near phytotoxic levels.
Weeds from broiler litter. Studies in Alabama and North Carolina have shown rather conclusively that weeds are not transported in fresh broiler litter. However, high rates of broiler litter can stimulate weed seed already present to germinate.

Conclusions

Broiler litter can be used effectively as a source of N for cotton. Total N is almost as effective as N from ammonium nitrate fertilizer. In 4 of 7 site-years research in Alabama, total N in broiler litter was as effective as the total N in ammonium nitrate in increasing seed cotton yields. In other years, more N as broiler litter was needed. However, rates as high as 4 tons per acre or 240 pounds N per acre as broiler litter had no negative effects on cotton yields. In some cases, the higher rates as broiler litter enhanced yields. Pix was effective in enhancing yields in only 1 of 7 site-years. This was at the TVS location in 1992 when yields averaged over 3 bales per acre. There is some residual N effect from high rates (4 tons/acre) of broiler litter. However, at lower, recommended rates, this residual effect is not high enough to reduce the recommended N for cotton. Effective rates of broiler litter would be 2-3 tons per acre or between 120 and 180 pounds total N per acre. This can be applied at planting. (See Table 1.)

Table 1. Effect of annual ammonium nitrate, broiler litter, and Pix® applications on cotton lint yields at Tennessee Valley Substation (TVS) in North Alabama on a Decatur silty clay loam and at E. V. Smith Research Center (EVS) in Central Alabama on a Norfolk f.s.l.
Nitrogen Source	N rate lb/acre	Location and Year
		- - - - - - TVS - - - - - -			- - - - - - - - EVS - - - - - - - -
		1990	1991	1992	1991	1992	1993	1994
		- - - - - - - - - - Pounds of lint per acre - - - - - - - - - -
None	0	720	360	950	730	400	740	420
Ammonium nitrate Ammonium nitrate* Ammonium nitrate Ammonium nitrate*	60 60 120 120	870 940 960 950	400 420 480 460	1570 1600 1840 1970	920 940 1010 1110	800 810 980 1010	820 840 840 740	820 850 1010 980
Broiler litter Broiler litter Broiler litter	120 180 240	960 1000 980	470 480 530	1680 1020 1860	1030 1050 1210	740 800 1010	770 890 730	800 810 850
Broiler litter* Broiler litter* Broiler litter*	120 180 240	850 900 1120	480 480 560	1770 1960 1860	1050 1230 1290	730 940 900	760 850 860	880 820 760
Mean L.S.D. (P<.10)		930 180	460 90	1710 170	1050 190	830 140	800 ns	820 180
*Pix applied; 60 pounds of N is approximately equivalent to 1 ton of broiler litter.

References

Bitzer, C.C., and J.T. Sims. 1988. Estimating the availability of nitrogen in poultry manure through laboratory and field studies. J. Environ. Qual. 17:47-54.

Castellanos, J.Z., and P.F. Pratt. 1981. Mineralization of manure nitrogen--correlation with laboratory indexes. Soil Sci. Soc. Am. J. 45:354-357.

Mitchell, C.C., and C.E. Browne. 1992. Plant nutrient availability in fresh and composted poultry wastes. Proc. 1992 Nat. Poultry Waste Management Symp. p. 391-395.

Mitchell, C.C., J.O. Donald, and J. Martin. 1989. The value and use of poultry waste as fertilizer. Ala. Coop. Ext. Serv. Cir. ANR-244. Auburn University, AL.

Predicting N Availability - A Research Footnote

Predicting N availability from animal manures is elusive. Bitzer and Sims (1988), using a predicted available N in poultry litter of 80% of inorganic N and 60% of organic N, found values ranging from 54 to 118% of the predicted value. They concluded that while their predicted available N was ". . . reasonably successful, (it) consistently overestimated the amount of available N in the manures." Much of the available N was released during the first few weeks after application (Bitzer and Sims, 1988; Castellanos and Pratt, 1981). Others have reported N availability factors of 75% the first year (USDA, 1979) to near 50% (Mitchell and Browne, 1992). Nitrogen management for cotton is difficult. However, from a practical, crop management standpoint, these data suggest that defining a precise N availability index is not essential to managing broiler litter as a source of N for cotton.

Source:
Mitchell, C.C., C.H. Burmester, and K.L. Edmisten. 1991. Cotton fertilization management in Alabama. Ala. Coop. Ext. Serv. Cir. ANR-619. Auburn University, AL.
Mitchell, C.C., C.H. Burmester, C.W. Wood, and K.L. Edmisten. 1992. Broiler litter on cotton: 1990 and 1991 test/demonstration results. New Tech. Demo. Rep. No. S-03-92. Ala. Coop. Ext. Serv., Auburn University, AL.
Mullins, G.L., and B.F. Hajek. 1997. Phosphorus accumulation and loss from Alabama soils receiving poultry litter. Ala. Agric. Exp. Stn. Bul. No. 631. Auburn University, AL.
USDA. 1979. Animal waste utilization on cropland and pastureland. Utilization Rep. no. 6. Washington, DC. Science and Education Admin.

Additional information about using poultry manures as fertilizer can be found at:

"The Value and Use of Poultry Manures as Fertilizer".

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