Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/17/2010
Publication Date: 1/1/2011
Citation: Tewolde, H., Adeli, A., Rowe, D.E., Sistani, K.R. 2011. Cotton lint yield improvement attributed to residual effect of repeated poultry litter application. Agronomy Journal. 103:107-112. Interpretive Summary: Poultry litter applied to fertilize crops in one season affects crop production in subsequent seasons. But the magnitude of this carryover effect and the possibility to reduce the application rate in subsequent seasons is not well known. A study on a private farm in the Mississippi Delta was conducted over six years to estimate the contribution of moderate rates of broiler litter applied in previous years on cotton lint yield in subsequent years. The results showed that the rate of litter to fertilize cotton may be reduced after only a few years of application. Yearly application of 3 ton/acre litter did not supply sufficient fertilization for optimum cotton lint yield during the first 3 years in 2002-2004, but continued application of the same rate was found to be sufficient fertilization in the last 3 years starting in the fourth year in 2005. This shows yearly litter application for three consecutive years had enough carryover to meet the fertilization deficit of 3 ton/acre litter application in the fourth year. However, the carryover amount was determined to be equivalent to less than 32 lbs/acre nitrogen, which is only approximately 6% of the total nitrogen applied in the first 3 years. The results of this research overall show that repeated litter application for a few years builds soil productivity gradually and the rate might be reduced in subsequent years while maintaining optimum lint yield. These results also confirmed our earlier finding that fertilizing cotton with 2 ton/acre litter supplemented with about 60 lbs/acre fertilizer nitrogen can replace all commercial fertilizers for optimum cotton lint yield in the Mississippi delta soils.
Technical Abstract: The magnitude of any poultry litter carryover and the possibility to decrease the rate of litter applied to soils with only a few years of application history is not documented. The objective of this research was to determine and quantify the contribution of carryover effect of moderate rates of broiler litter application to cotton on lint yield in subsequent years. Cotton was fertilized with 0, 2.2, 4.5, 6.7 Mg ha-1 yr-1 broiler litter, 4.5 Mg ha-1 yr-1 litter plus 67 kg ha-1 yr-1 as urea ammonium nitrate (UAN), or with commercial inorganic fertilizers (farm standard, Std) on a private farm under conventional till in Mississippi in 2002-2007. In 2005, after fertilizing at the same annual rates for 3 yr (2002-2004), each plot was divided into two equal subunits and one half continued to receive the same fertilization treatment and the other half was not fertilized in the subsequent 3 yr (2005-2007). The results with continued fertilization showed lint yield with the 6.7 Mg ha-1 litter fertilization, which did not supply sufficient fertilization for optimum lint yield during the first 3 yr, equaled or exceeded that of the Std in the last 3 yr (2005-2007), suggesting a cumulative litter carryover in 2002-2004 was sufficient to meet the fertilization deficit. The amount of carryover was equivalent to <35 kg ha-1 N, which is only ˜6% of the 543 kg ha-1 total N applied in 2002-2004. The carryover effect was less apparent on lint yield when the litter rate was <6.7 Mg ha-1. The results of this research overall show that repeated litter application for a few years under conventional till management builds soil productivity gradually and the rate might be reduced in subsequent years while maintaining optimum lint yield. These results also confirm our earlier finding that fertilizing cotton with 4.5 Mg ha-1 litter supplemented with about 67 kg ha-1 inorganic N can replace conventional fertilization with inorganic fertilizers for optimum cotton yield.