ABSTRACT

Conservation tillage and waste management are manipulative strategies for sequestering carbon in the soil in the cotton belt, where a large amount of poultry litter and mulch-till (MT) systems, surface application of poultry litter (PL), and winter rye (Secale cereale L.) cover crop on soil pH, soil organic matter (SOM), soil C and N concentrations and growth and yield of cotton (Gossypium hirsutum L.) was initiated in 1996 at Alabama Agriculture Experiment Station, Belle, Mina, AL. Five years of using the above treatments did not significantly affect soil pH. In 2001 and 2002, the effects of tillage, cover cropping and PL treatments on total soil C and total soil N were significant in the top 0-5 cm soil profile, due to the accumulation of organic residues from the crops and PL at the soil surface. In 2001, MT had 31% and 17% greater (P< 0.05) SOM compared to bare fallow and no-till respectively. Mulch-till had 47% and 51% greater (P<0.05) soil C than BF system in 2001 and 2002, respectively in the 0-5 cm soil profile. Cover cropping significantly increased soil C compared to BF and cotton winter-fallow (CF) systems by 42% and 25% respectively in the top 0-5 cm soil profile in 2001. Similar figures for 2002 were 48% and 21% respectively. Plots which received 200 kg N ha^-1 in the forming the form PL had 35% greater (P< 0.05) soil C in the 0-5 cm compared to the 0 kg N ha^-1 treatment in 2001. In 2002 the 100 kg N ha^-1 AN, 100 kg N ha^-1 PL and 200 kg N ha^-1 PL had 27%, 31%, and 54% greater (P< 0.05) soil C in the 0-5cm profile compared to the 0 kg N ha^-1 treatment, respectively. Compared to 2001, soil C for each treatment at each depth was greater in 2002. In 2001, total soil N in the 0-5 cm profile under NT and BF was 30% and 42% significantly lower than that under MT respectively. In 2002, total soil N under BF was 40% lower than that under CT and MT and 30% lower than that under NT. Total soil N in the 0-5cm profile under CR was 17% and 42% greater than that in CF and BF plots respectively, in 2002. In 2002, total soil N in the 0-5cm soil profile in plots which received 200 kg N ha^-1 PL was 54%, 29%, 20% greater than in plots which received 0 kg N ha^-1, 100kg N ha^-1 AN, 100 kg N ha^-1 PL treatments, respectively. There was no significant accumulation on N in the deeper soil profile due to PL at 200 kg N ha^-1 treatments would be ideal for increasing total SOM and soil C in cotton plots.