Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2009
Publication Date: 11/1/2009
Citation: Reddy, S.S., Nyakatawa, E.Z., Reddy, K.C., Raper, R.L., Reeves, D.W., Lemunyon, J.L. 2009. Long-term effects of poultry litter and conservation tillage on crop yields and soil phosphorus in cotton-cotton-corn rotation. Field Crops Research. 114:311-319. Interpretive Summary: To fully realize the benefits and deficiencies of conservation tillage and poultry litter application on cotton production, a long-term field study was initiated in 1996. Results from 2003-08 were discussed in this paper. All three tillage practices; conventional tillage (CT), mulch tillage (MT) and no-tillage (NT) had similar cotton lint yields with application of ammonium nitrate (AN) at 100 kg N ha-1. On average, 12 and 11% yield reductions were observed in NT when receiving PL at 100 kg N ha-1 compared to CT and MT, respectively. However, NT plots with PL application at a double rate (200 kg N ha-1) gave similar yields to that of CT and MT either with PL or AN at 100 kg N ha- 1. Winter rye cover crop increased lint yields significantly in CT plots. During corn years, where corn was grown as a rotational crop, highest residual fertility of PL was observed in NT plots in terms of corn grain yields. Status of soil pH and available P were studied 12 years after initiation of the experiment (after 8 PL applications) and were compared with initial values in 1996. Results showed that PL application at 100 kg N ha-1 helped in maintaining original pH in CT and MT plots, but it was not ufficient to maintain pH in NT plots. Application of PL at 100 kg N ha-1 helped in maintaining original available P levels in all tillage practices while use of AN decreased available P. Quantity of P applied through PL was with in the range of crop requirements and it helped in preventing build up of soil P. Further, the corn crop rotation served as a scavenger on the residual fertility. However, although non-significant, elevated levels of P in all tillages with application of PL at 100 kg N ha-1 compared to 1996 levels indicate that there is possibility of significant build up of P with further application of PL at the same rate. Application of a higher rate of PL (200 kg N ha-1) in NT plots resulted in build up of P. It can be concluded that NT gives similar yields to CT when received AN at a similar rate, but needs higher rates of PL to achieve similar yields to CT. No-tillage with winter rye cover crop gave similar yields to CT. Considering the fact that higher rate of PL (200 kg N ha-1) leads to P build up in soil, the no-tillage with PL application at 100 kg N ha-1 combined with a winter cover crop and corn rotation can be recommended for a sustainable cotton production in south eastern USA. Further studies are needed to find out suitable PL application rates between 100-200 kg N ha-1 for a NT system that gives comparable yields to CT without affecting soil quality.
Technical Abstract: Long-term field experiments are needed to fully realize positive and negative impacts of conservation tillage and poultry litter application. A study was initiated on a Decatur silt loam soil at the Tennessee Valley Research and Extension Center, Belle Mina, AL, USA in 1996 to evaluate cotton (Gossypium hirsutum L.) performance with long-term poultry litter (PL) application under different tillages and to study the build up of phosphorus (P) with application of PL. Treatments include incomplete factorial combinations of three tillage systems [conventional till (CT), mulch-till (MT), and no-till (NT)], two cropping systems [cotton- fallow and cotton-winter rye (Secale cereale L.)], and two nitrogen sources and rates [100 kg N ha-1 from ammonium nitrate (AN), and 100 and 200 kg N ha-1 from poultry litter (PL)]. Cotton was rotated with corn (Zea mays L.) every third year. Results from 2003-2008 showed that all tillages gave similar cotton lint yields with AN at 100 kg N ha-1. Application of PL at 100 kg N ha-1 in NT plots resulted in 12 and 11% yield reductions compared to that of CT and MT, respectively. However, NT plots with higher quantity of PL (200 kg N ha-1) gave similar yields to CT and MT at 100 kg N ha-1. During corn years, higher residual fertility of PL, in terms of grain yields, was observed in NT plots compared to CT and MT. Long-term PL application (100 kg N ha-1 yr-1) helped to maintain original soil pH in CT and MT while AN application decreased soil pH. In NT plots, PL at 100 kg N ha-1 was not sufficient to maintain original soil pH, but 200 kg N ha-1 maintained original pH. Although not significant, elevated P levels were observed in all tillages compared to original P levels which indicates possibility of P build up in future with further application of PL. Application of PL at double rate (200 kg N ha-1) in NT plots resulted in significant build up of P. Results indicate that NT gives similar yields to CT when received AN, but needs higher rate of PL application to achieve similar yields to CT.