Doctor of Philosophy (PhD)


Plant, Environmental, and Soil Sciences

Document Type



This three-year study was conducted on a commerce silt loam soil at the Northeast Research and Experiment Station near St. Joseph, Louisiana to evaluate the following objectives: 1) evaluate crop yield response to tillage, winter, and summer cover crops in wheat double-cropping systems. 2) evaluate the effects of tillage, winter and summer cover crops on soil properties under different cropping systems. 3) quantify the economic benefits of double-cropping, cover cropping and monoculture systems under conventional and no tillage practices. A winter cover crop (WCC) mix (winter wheat (Triticum aestivum and Austrian winter pea (Pisum sativum) and summer cover crop (SCC) mix sunn hemp (Crotalaria juncea) and sorghum sudangrass (Sorghum bicolor) were incorporated in the treatments (cropping systems). Treatments included conventional tillage (CY)and no-tillage (NT) while the cropping systems are wheat-fallow (W-F), wheat-cotton (W-C), wheat-soybean (W-S), wheat-summer cover crops (W-SCC), WCC-S, F-C,WCC-S and W-S. Tillage influence on crop yield were not consistent and varied across years. In year one wheat yield in the NT (2091 kg ha-1) was 8.5% greater than the wheat yield in the CT (1913 kg ha-1). In year two and three, wheat yield in the CT was higher than the NT and was significantly than the NT in year three with the CT (2621 kg ha-1) outyielding the NT (2140 kg ha-1) with 18.4%. On a three-year average, wheat yield in the CT (2122 kg ha-1) were relatively higher than the NT (1961 kg ha-1) with 7.6%. Like the wheat, tillage influence on cotton and soybean yield followed the same trend with the CT having higher yield than the NT. In general, the fallow system for each cropping system treatment had the lowest yield compared to double-cropping and cover cropping treatments. Soybean yield in the W-S (4107 kg ha-1) and WCC-S (3780 kg ha-1) treatments were 18.6 and 11.5% respectively higher than the F-S (3345 kg ha-1). On a three-year average this yield advantage of the double-cropped and cover cropping systems was also observed in wheat and cotton. Tillage and cropping system influence on soil properties followed same pattern with the fallow systems have the least influence on soil properties. The CT tend to improve soil properties more at the 0 -15 cm soil depth, a layer within the depth of our CT where most of the residues were incorporated. This is one reason why our soil organic matter in the CT at the 0 -15 cm soil depth were more than that of the NT and it was significant in the cotton cropping system in one year with the CT having 1.65% while the NT was 1.45%. Beyond the top 0 -15 cm soil depth, the NT seems to accumulate more soil organic matter. Cropping systems with cover crops and double-cropped systems had the highest soil organic matter in all cropping systems. The highest soil organic matter of 1.81% was observed in both W-SCC and WCC-S at the 0 -15cm soil depth. Evidently, we observed lower bulk densities in the NT but no significant difference between tillage practice or cropping systems. The CT had the highest bulk density of 1.35 g cm-3compared to the NT with 1.27 g cm-3 across all cropping systems. Our results also demonstrated that cropping system treatments with cover crops incorporated (W-SCC) and double-cropped systems (WCC-C and WCC-S) had higher net returns compared to the fallow systems (W-F, F-C and F-S).



Committee Chair

Fultz, Lisa M.