PT  - JOURNAL ARTICLE
AU  - H.A. Torbert
AU  - R.D. Harmel
AU  - K.N. Potter
AU  - M. Dozier
TI  - Evaluation of some phosphorus index criteria in cultivated agriculture in clay soils
DP  - 2005 Jan 01
TA  - Journal of Soil and Water Conservation
PG  - 21--29
VI  - 60
IP  - 1
4099  - http://www.jswconline.org/content/60/1/21.short
4100  - http://www.jswconline.org/content/60/1/21.full
AB  - There are growing concerns regarding the fate of nutrients from land application of animal waste. In recent years, phosphorus (P) indices have been developed to provide information regarding nutrient loss potentials from animal waste application methods and topography. However, in many cases, these P indices have not been fully tested, especially in cultivated agriculture. Three factors commonly utilized in soil P indices for manure management are manure rate, manure incorporation, and slope. Rainfall simulations were conducted to examine the impact of these three factors on runoff losses of P on heavy clay soils under cultivated agriculture. Four manure litter (turkey litter) application rates (0, 4.5, 9.0, and 13.5 Mg ha−1 (0, 2, 4, and 6 tons ac−1)) were applied on two different slopes (5 and 9 percent) on a Heiden clay (fine, smectitic, thermic Udic Haplusterts). The litter was surface applied to a corn (Zea mays L.) production area, with or without incorporation. The four application rates were also applied to a permanent bermudagrass (Cynodon dactylon (L.) Pers.) pasture on a 5 percent slope. A rainfall simulator was used to generate water runoff for 30 minutes from 1.5 by 2.0 m (5 by 6.5 ft) plots. Runoff samples were analyzed for runoff volume, sediment, sediment nitrogen (N) and P, dissolved ammonia nitrogen (NH4-N), nitrate nitrogen (NO3-N), and PO4-P. The results were analyzed using regression analysis techniques based on application rates. The dissolved NO3-N concentration was not affected by either litter incorporation or slope in the cultivated sites, but was greatly increased with increasing litter application rate in the pasture sites. Increased losses of dissolved NH4-N and PO4-P were observed with increasing litter application rate, with a significant reduction in losses observed when litter was incorporated. However, increased slope did not significantly impact the level of runoff losses of dissolved NH4-N and PO4-P.