Effects of reduced tillage and fertilizer application method on plant growth, yield, and soil health in organic bell pepper production

• Rolled cover crop residue effectively suppressed weeds between pepper rows.
• Conservation tillage produced similar yields as conventional tillage in 2014.
• Strip-tillage increased mean soil temperature over no-tillage system in 2014 and 2015.
• Microbial diversity trended to be higher in conservation than conventional tillage.

Concerns over soil erosion and nitrate leaching have generated interest in cover crop-based reduced tillage systems. A 2-year field study was conducted in Ames, IA in 2013–14 and 2014–15 to compare cover crop-based no tillage (NT) and strip tillage (ST) with conventional tillage (CT) in production of organic bell pepper (Capsicum annuum L.). Two fertility treatments – preplant fertilizer only, or application split between preplant and post-planting fertigation – which applied the same amount of total N (90 kg ha−1), were also evaluated. The experimental design was a split plot randomized complete block design with tillage as the whole plot (NT, ST, or CT) and fertility as the subplot treatment (preplant or split). A mixture of cereal rye and hairy vetch was seeded in September 2013 and September 2014 in all plots. The cover crop was terminated in mid-May using tillage in CT plots and in early June using a roller-crimper in NT and ST plots. Data were collected on plant growth, yield, soil temperature and moisture, weed suppression, nitrate leaching, and microbial biomass and diversity. Marketable yields were equal among tillage treatments in 2014, but higher for CT in 2015, with no difference between NT and ST. Preplant fertility increased yield in 2014, but yields were lower in the preplant fertility treatment in 2015. Leaf N concentration was higher in CT than NT and ST, but plant height, stem diameter, and dry weight were similar across all treatments. Soil temperature was generally highest for CT and higher in ST than NT in one out of three instances. Soil moisture was unaffected by tillage in 2014, but was higher under NT and ST from June to late-August in 2015. The rolled cover crop mulch in NT and ST plots effectively suppressed annual weeds during period between planting and the first weeding event, reducing weed biomass and density compared to CT. Nitrate-N concentration in leachate was reduced under NT and ST only during early sampling dates in 2014. Soil microbial biomass and diversity were similar among tillage treatments on most sampling dates, but consistently higher in the 0–7.5-cm than the 7.5–15-cm soil profile. Results indicate the potential for NT and ST yields to be comparable to CT, but temperature and nitrogen may limit yield under some circumstances. Though observed only periodically in this study, benefits of cover crops and reduced tillage to soil health and water quality make organic NT and ST systems promising in addressing current environmental concerns in agriculture.