| | Figure 1: Soil organic matter (%) at 0-6” following poultry litter (PL) best management practices. |
|
| | Figure 2: Soil phosphorus (ppm) at 0-6” following poultry litter (PL) best management practices. |
|
| | Figure 3: Soil potassium (ppm) at 0-6” following poultry litter (PL) best management practices. |
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The major benefit of using poultry litter in a cotton production system is that it can be a source of essential major nutrients such as nitrogen, phosphorous, and potassium, and many micronutrients (Table 1). A potential benefit of using poultry litter as a fertilizer in addition to supplying nutrients is that it also helps maintain or increase soil organic matter. An ongoing study started in 1998 at the LSU AgCenter’s Red River Research Station in Bossier City, La., has shown an increase in soil organic matter when using poultry litter (Figure 1). Organic matter can serve as a major reservoir for nitrogen and phosphorus in the soil and also enhances soil structure, increasing water-holding capacity and water-infiltration rates.
Although there are obvious benefits to using poultry litter in cotton production, there are also potential concerns. One concern is that repeated application of poultry litter year after year based on nitrogen needs can result in accumulation of phosphorus in the soil. Results from this study show that after 10 years of continually using poultry litter, phosphorus levels were 3 to 4 and 6 times greater in soil where applications of 2 tons and 4 tons of poultry litter per acre, respectively, have been applied compared to the more traditional practice of fertilizing with inorganic nitrogen fertilizer (Figure 2). These levels are based on soil sampled at 0 to 6 inches in 2008 – 10 years after the beginning of this study.
To avoid this potential problem, poultry litter can be applied based on how much phosphorus -- instead of nitrogen -- is needed in a particular field and then supplementing extra needed nitrogen with inorganic fertilizer. Phytoremediation, the process of using plants to take up excess soil chemical components, can also be used to avoid problems. For example, annual ryegrass grown in the winter and then removed for forage prior to planting cotton can help remove excess phosphorous and thus avoid accumulation over time. Potassium is another major nutrient supplied by poultry litter. This study shows an increased amount of potassium in the soil when using poultry litter (Figure 3).
Table 1. Micronutrients at Soil Depth 0-6"
|
Treatment |
Calcium
(ppm) |
Copper
(ppm) |
Magnesium
(ppm) |
Sulfur
(ppm) |
Zinc (ppm) |
|
Conventional Tillage + 60 lbs. N / A |
1215.78 |
2.01 |
374.26 |
14.04 |
1.21 |
|
Conservation Tillage + 60 lbs. N / A |
1105.58 |
1.89 |
348.87 |
11.89 |
1.22 |
|
Conventional Tillage + 2 tons PL / A |
1088.15 |
4.07 |
322.53 |
12.87 |
4.32 |
|
Conservation Tillage + 2 tons PL / A |
1257.57 |
4.53 |
354.13 |
16.86 |
5.21 |
|
Conservation Tillage + tons PL / A |
1265.43 |
6.36 |
348.38 |
17.35 |
7.73 |