Ecosystem Services and Cash Crop Tradeoffs of Summer Cover Crops in Northern Region Organic Vegetable Rotations

Abstract

Intensive production practices characterizing vegetable farming contribute to high productivity, but often at the expense of supporting and regulating ecosystem services. Diversification with cover crops may support increased resilience through soil organic matter (SOM) contributions and physical soil protection. Vegetable farming often includes spring and fall production, limiting establishment and productive potential of over-wintered cover crops that are more widely used in the USA. In northern climate vegetable systems, warm-season cover crops planted during short summer fallows could be a tool to build resilience via ecosystem service enhancement. This project evaluated summer cover crops in the northern USA (MN and WI) for biomass accumulation, weed suppression, and contribution to fall cash crop yield. Our study included four site years, during which we investigated the effects of four cover crop species treatments, grown for 30 (short duration, SD) or 50 days (long duration, LD) alongside bare fertilized and unfertilized control treatments: buckwheat (Fagopyrum esculentum) and sunn hemp (Crotalaria juncea) monocultures, and biculture of chickling vetch (Lathyrus sativus) or cowpea (Vigna unguiculata) with sorghum-sudangrass (sudex) (Sorghum bicolor x S. bicolor var. Sudanese). To quantify cover crop quantity, quality, and weed suppression capacity, we measured cover crop and weed biomass, and biomass C:N. To quantify effects on cash crops, we measured fall broccoli yield and biomass. Mean total biomass (cover crop + weeds) by site year ranged from 1,890 kg ha−1 in MN Y1 to 5,793 kg ha−1 in WI Y2 and varied among species in Y1 for both the SD and LD treatments. Most cover crops did not outcompete weeds, but treatments with less weeds produced more overall biomass. Data from Y1 show that cover crops were unable to replace fertilizer for fall broccoli yield, and led to reduced fall crop yield. Broccoli in Y2 did not reach maturity due to fall freeze. Summer cover crops, because of their biomass accumulation potential, may be used by farmers in northern climates to fit into cropping system niches that have historically been left as bare soil, but care with timing is necessary to optimize weed suppression and mitigate tradeoffs for cash crop production.

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

“…Positive effects on soil N indicators were observed in cover cropped plots both during growth and following termination and incorporation of biomass. Cover crop production initially reduced ExN during growth relative to the bare ground control, suggesting that cover crops in our region may carry out critical N retention ecosystem services that result in removal of soil N at risk of loss during periods with no cash crop growth (Wauters et al, 2021). This cover crop N retention role may be important in Minnesota high tunnels during periods when farmers remove plastic in winter months, about every 3-4 years before plastic replacement, and precipitation events could impact soil N movement.…”

Optimizing crop rotations via Parrondo’s paradox for sustainable agriculture

“…Crop rotations have been proposed as a means of tackling multiple issues of modern-day agriculture—being able to control insects, pests and diseases of crops, control weeds, increase crop yields, lower economic risk, reduce toxic substance accumulations in soils, achieve abundant and lasting soil cover, maintain or increase soil organic matter (SOM) content, provide alternating root systems allowing for a stable extraction of nutrients favouring soil equilibrium, improve soil structure and ultimately promote greater biological diversity [ 25 ]. Crop rotation, are thus, a sustainable component of conservation agriculture able to increase the SOM and physical soil protection [ 26 , 27 ]. However, a significant obstacle lies in deriving optimum rotation schedules due to external uncertainties.…”

Suppression of weed and insect populations by living cover crop mulches in organic squash production

“…Environmental impacts of runoff and erosion can be mitigated in plastic mulch systems by planting living cover crops between the plastic-covered beds (Arnold et al, 2004). The use of cover crops between rows can also reduce the long term weed seedbank while providing additional ecological services (Liebman et al, 1997;Baraibar et al, 2018;Wauters et al, 2021). Cover crops can suppress weeds through direct competition (Hiltbrunner et al, 2007;Bezuidenhout et al, 2012;Brust et al, 2014) and by generating residues which can suppress weed emergence through physical (mulch) effects, release of allelochemicals, and changes in nutrient dynamics (Teasdale and Mohler, 2000;Sarrantonio and Gallandt, 2003;Teasdale et al, 2012).…”