Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 30, 2005
Publication Date: May 13, 2005
Citation: Tewolde, H., Sistani, K.R., Rowe, D.E. 2005. Broiler litter as a micronutrient source for cotton: concentrations in plant parts. Journal of Environmental Quality. 34:1697-1706. Interpretive Summary: The vast majority of the litter produced by the chicken industry is land-applied as a fertilizer to meet the nitrogen and phosphorus needs of crops. The value of litter as a source of micronutrients is not as appreciated and investigated as is its value as a source of N and P. Litter contains nearly all micronutrients essential for plant growth but the extent of availability of these micronutrients for plant absorption is not well understood. In this research, tissue analysis of the concentration of iron, copper, zinc, and manganese, all of which are essential plant micronutrients, showed that broiler litter supplies adequate amounts of iron, copper, and manganese to cotton plants grown in a greenhouse. However, cotton did not receive enough zinc from litter probably because Zn was not efficiently absorbed by cotton roots. The results of this research also showed that more than 90% of the micronutrients applied with the litter are not removed by cotton and have the potential to accumulate if litter is used as the primary cotton fertilizer. These results should be useful for nutrient management planning purposes.
Technical Abstract: The value of poultry litter as a source of micronutrients is not as appreciated and recognized as its value as a source of the macronutrients N, P, and K. Analytically, litter contains nearly all essential micronutrients but the extent of phytoavailability of these nutrients and whether cotton and other crop plants can receive adequate amounts of these nutrients from litter is not well understood. The objective of this research was to determine whether cotton receives sufficient amounts of Fe, Cu, Mn, and Zn from litter and estimate the efficiency of cotton in extracting these metal nutrients from litter in the absence of any other source of the micronutrients. The greenhouse research used plastic pots filled with '11 kg of 2:1 (v/v) sand: vermiculite growing mix. Cotton cv. Stoneville 474 was grown in the pots fertilized with poultry litter at rates of 30, 60, 90, or 120 g pot-1 in a factorial combination with four supplemental nutrient solution (NS) treatments. The nutrient solutions were full Hoagland's nutrient solution (NS-full); a solution of the macronutrients N, P, K, Ca, and Mg (NS-macro); a solution of the micronutrients B, Fe, Zn, Mn, Cu, and Mo (NS-micro); and water (NS-none). Based on tissue nutrient analysis, a one-time broiler litter application supplied adequate amounts of Fe, Cu, and Mn to bring the concentration of these nutrients in upper leaves within published sufficiency ranges. Zinc, with <17 mg kg-1 concentration in the upper leaves, is the only micronutrient that was below the established sufficiency range regardless of the rate of applied litter. Cotton extracted Fe and Mn with better efficiency than Cu or Zn, removing as much as 9.1% of Fe and 7.2% of Mn supplied by 30 g pot-1 litter. In contrast, the extraction efficiency was 1.7% for Cu and 1.9% for Zn. Increasing the litter rate decreased the extraction efficiency of all four micronutrients to lows of 3.3% Fe, 2.9% Mn, 1.3% Cu, and 0.8% Zn with 120 g pot-1 litter with no supplemental nutrient solution. Roots accumulated 57% of the total absorbed Fe and 66% of Cu, and leaves accumulated 30% of Fe and only 12% of Cu supplied by litter. These results demonstrate that broiler litter is valuable sources of the metal nutrients supplying Fe, Cu, and Mn in full and Zn in part, but a very large fraction of the litter-supplied metal nutrients remain in the soil.