Exploring Overwintered Cover Crops as a Soil Management Tool in Upper-midwest High Tunnels

High tunnels are an important season extension tool for horticultural production in cold climates, however maintaining soil health in these intensively managed spaces is challenging. Cover crops are an attractive management tool to address issues such as decreased organic matter, degraded soil structure, increased salinity, and high nitrogen needs. We explored the effect of winter cover crops on soil nutrients, soil health and bell pepper (Capsicum annuum) crop yield in high tunnels for 2 years in three locations across Minnesota. Cover crop treatments included red clover (Trifolium pratense) monoculture, Austrian winter pea/winter rye biculture (Pisum sativum/Secale cereale), hairy vetch/winter rye/tillage radish (Vicia villosa/S. cereale/Raphanus sativus) polyculture, and a bare-ground, weeded control. Cover crop treatments were seeded in two planting date treatments: early planted treatments were seeded into a standing bell pepper crop in late Aug/early September and late planted treatments were seeded after bell peppers were removed in mid-September At termination time in early May, all cover crops had successfully overwintered and produced biomass in three Minnesota locations except for Austrian winter pea at the coldest location, zone 3b. Data collected include cover crop and weed biomass, biomass carbon and nitrogen, extractable soil nitrogen, potentially mineralizable nitrogen, microbial biomass carbon, permanganate oxidizable carbon, soil pH, soluble salts (EC), and pepper yield. Despite poor legume performance, increases in extractable soil nitrogen and potentially mineralizable nitrogen in the weeks following cover crop residue incorporation were observed. Biomass nitrogen contributions averaged 100 kg·ha−1 N with an observed high of 365 kg·ha−1 N. Cover crops also reduced extractable soil N in a spring sampling relative to the bare ground control, suggesting provision of nitrogen retention ecosystem services.

Impact of crop residues and biopreparations on nitrogen changes in Haplic Luvisol – model experiment

Agroecosystem crop residues are considered to be a primary resource of organic substances, and are subject to the different transformation processes in the soil environment. The decomposition processes of organic substance can be also regulated by the application of the different biopreparations. The decomposition of organic substances in soil also causes changes in nitrogen content and its forms. It is essential for farmers to know about these processes in order flexibly to regulate and affect the transformation processes of the applied crop residues via the biopreparations directly in the production conditions. The changes of content and forms of nitrogen and its calculated parameters in Haplic Luvisol influenced by the applied crop residues (wheat – WR, rape – RR) and biopreparations (Betaliq, Trichomil) were monitored in the small-pot experiment carried out at the Department of Soil Science (FAFR, SUA-Nitra). The laboratory experiments were established for the incubation period 4, 7, 14, 28, 60, 90 and 180 days. The applied crop residues had statistically significant impact on the contents of total nitrogen (Nt) and potentially mineralizable nitrogen (Npot) and inorganic forms N, similarly also the values of labile nitrogen (LN) and nitrogen pool index (NPI). The biopreparations affected statistically significantly the average values Npot, LN, nitrogen lability index (NLI) and nitrogen management index (NMI). During the incubation period, the contents Npot and values LN and other calculated indexes of nitrogen fluctuated significantly.