Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2006
Publication Date: 4/1/2007
Citation: Tewolde, H., Sistani, K.R., Rowe, D.E., Adeli, A. 2007. Nitrogen Extraction by Cotton Fertilized with Broiler Litter. Crop Science. 47:1131-1142. Interpretive Summary: Poultry litter, which is generated in large quantities in the same southeastern US states where both poultry and cotton are dominant agricultural enterprises, can be used as a primary row crop fertilizer. But loss of litter-derived nutrients to the immediate environment is a concern of contamination and pollution. Nitrogen is one of the most important litter nutrients that may not be efficiently extracted and may therefore detrimentally affect the environment. This research determined the magnitude and efficiency of nitrogen extraction and utilization by cotton fertilized with broiler chicken litter with or without supplemental inorganic nitrogen fertilizer. The results demonstrate that cotton extracts nitrogen equivalent to the amount that may be supplied by as much litter as 2 or 3 tons per acre when supplemented with inorganic nitrogen fertilizers. While nearly 60% of the total extracted nitrogen is removed from the soil in harvested crop, an amount equivalent to the remainder is bound in plant tissues with little or no risk of becoming released to the immediate environment until the plant parts decompose and release the nitrogen bound in plant tissues. Nitrogen extraction efficiency, sometimes referred to as apparent nitrogen recovery, averaged across years was 30% under no-till cotton production system compared with 62% under conventional-till production system. The substantially lower nitrogen extraction efficiency under the no-till than under the conventional-till probably indicates that a greater fraction of the litter-derived nitrogen is lost to volatilization and runoff under the no-till than under the conventional-till. When compared with reported nitrogen uptake of forage grasses, these results suggest that cotton may be as ideal as or more ideal than grass crops on which litter can be used as a fertilizer.
Technical Abstract: Inefficient extraction of litter-supplied N and its loss to the immediate environment is a concern when poultry litter is used as a primary row crop fertilizer. This research determined the magnitude and efficiency of nitrogen extraction and utilization by cotton (Gossypium hirsutum L.) fertilized with broiler litter with or without supplemental inorganic N fertilizer. It was conducted on two commercial farms under conventional-till and no-till production systems in 2002, 2003, and 2004 in Mississippi, USA. Under each system, fresh broiler litter rates of 2.2, 4.5, and 6.7 Mg ha-1 were compared in an incomplete-factorial combination with 0, 34, or 67 kg ha-1 N as urea-ammonium nitrate solution (UAN). An unfertilized control and a farm standard fertilization were also included. Nitrogen extracted by aboveground plant parts was calculated as a product of N concentration and dry weight of each plant part taken from 0.5 to 0.6 m2 in the center rows. Litter up to 6.7 Mg ha-1 and UAN-N up to 135 kg ha-1 had a significant linear effect on N concentration in plant parts and on total N extracted. The best yielding treatments, 4.5 Mg ha-1 litter supplemented with 67 kg ha-1 UAN-N and the standard, respectively, extracted an average across years of 25 and 75% more N than applied under the conventional-till and 19%less N and 40% more N than applied under no-till. Nitrogen extraction efficiency, sometimes referred to as apparent N recovery, averaged across treatments and years was 62% under the conventional-till and 30% under the no-till. Approximately 59% of extracted N was partitioned to seed and lint which represents an amount that would be removed from the field. An average across years of 122 kg N ha-1 (conventional-till) and 114 kg N ha-1 (no-till) accumulated in the seed of treatments that received 4.5 Mg ha-1 litter plus 67 kg ha-1 UAN-N, with a corresponding accumulation in the seed of the standard treatment of 123 and 100 kg N ha-1. These results demonstrate cotton extracts N equivalent ('25%) to the amount that may be supplied by as much litter as 4.5 to 6.7 Mg ha-1 when supplemented with inorganic N.