Comparing cover crop research in farmer-led and researcher-led experiments in the Western Corn Belt

Cover crops can mitigate soil degradation and nutrient loss and can be used to achieve continuous living cover in cropping systems, although their adoption in the Western Corn Belt of the United States remains low. It is increasingly recognized that cover crop integration into corn (Zea mays L.)-based crop rotations is complex, requiring site and operation specific management. In this review, we compared on-farm, farmer-led field scale trials to researcher-led trials carried out in small plots on University of Nebraska-Lincoln experiment stations. Although there is a range of cover crop research conducted in the state, there is no synthesis of the scope and key results of such eorts. Common cover crop challenges and goals in the state are similar to those reported nationwide; challenges include adequate planting timing, associated costs, and weather, while a top goal of cover crop use is to improve soil health. Farmer-led trials most frequently compared a cover crop to a no-cover crop control, likely reflecting a desire to test a basic design determining site-specific performance. Both researcher-led and farmer-led trials included designs testing cash crop planting timing, while some portion of farmer-led trials tested cover crop seeding rates, which are directly related to reported cover crop challenges. Farmer-led trials were carried out on a greater variety of soils, including sandy soils, whereas sandy soils were absent from researcher-led trials. More than half of farmer- led experiments were conducted on fields with slopes of 6–17% while most researcher-led experiments were conducted on fields with slopes of \u3c1%. Mean cover crop biomass production was 600 kg/ha in farmer-led and 2,000 kg/ha in researcher-led trials. Crop yields were not significantly aected by cover crops in either farmer-led or researcher-led trials. Such comparisons demonstrate that in some instances, cover crop research is addressing challenges, and in some instances, it could be expanded. This synthesis expands our knowledge base in a way that can promote co-learning between dierent scales of experiments, and ultimately, reduce risks associated with cover crop management and further promote continuous living cover of agricultural landscapes

Cover crop planting practices determine their performance in the U.S. Corn Belt

Cover crop growing periods in the western U.S. Corn Belt could be extended by planting earlier. We evaluated both pre-harvest broadcast interseeding and post-harvest drilling of the following cover crops: (a) cereal rye (Secale cereale L.) [RYE]; (b) a mix of rye + legumes + brassicas [MIX1], (c) a mix of rye + oat [Avena sativa L.] + legumes + brassicas (MIX2), (d) legumes [LEGU]) and (e) a no cover crop control. These were tested in continuous corn (Zea mays L.) [corn–corn] and soybean [Glycine max (L.) Merr.]–corn systems [soybean–corn] at three sites in Nebraska for their effect on cover crop productivity, soil nutrients, and subsequent corn performance. At the sites with wet fall weather, pre-harvest broadcasting increased cover crop biomass by 90%, to 1.29 Mg ha−1 for RYE and 0.87 Mg ha−1 for MIX1 in soybean–corn, and to 0.56 Mg ha−1 and 0.39 Mg ha−1 in corn–corn, respectively. At the drier site, post-harvest drilling increased biomass of RYE and MIX1 by 95% to 0.80 Mg ha−1 in soybean–corn. Biomass N uptake was highest in pre-harvest RYE and MIX1 at two sites in soybean–corn (35 kg ha−1). RYE and sometimes mixes reduced soil N, but effects on P, K, and soil organic C were inconsistent. In soybean–corn, corn yields decreased by 4% after RYE, and in corn–corn, by 4% after pre-harvest cover crops. Site-specific selection of cover crops and planting practices can increase their performance while minimizing impacts on corn

Cover crop productivity and subsequent soybean yield in the western Corn Belt

Cover crops (CC) in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotations may prevent N loss and provide other ecosystem services but CC productivity in the western Corn Belt is limited by the short growing season. Our objective was to assess CC treatment and planting practice effects on CC biomass, spring soil nitrate concentrations, and soybean yield at two rainfed sites in eastern and one irrigated site in south-central Nebraska over 4 yr. Cover crop treatments (cereal rye [Secale cereale L.] [RYE] and a mix of rye, legume, and brassica species [MIX]) were planted by broadcast interseeding into corn stands in September (pre-harvest broadcast) or drilling after corn harvest (post-harvest drilled) and terminated 2 wk before planting soybean. Cover crop biomass and N uptake varied between years, but generally at the eastern sites, pre-harvest broadcasting produced more biomass than post-harvest drilling (1.64 and 0.79 Mg ha−1, respectively) and had greater N uptake (37 and 24 kg ha−1, respectively). At the south-central site, post-harvest drilling produced more than pre-harvest broadcasting (1.44 and 1.20 Mg ha−1, respectively). RYE had more biomass than MIX (1.41 and 1.09 Mg ha−1, respectively), but the same N uptake. Soil nitrate reductions after CC were small. In 3 of 12 site-years, soybean yielded less after pre-harvest CC. Yield reductions were not correlated to CC biomass, but were likely due to greater weed pressure. High CC productivity is necessary for high N uptake, and requires site-specific selection of planting practice and CC treatments

Cover Crops have Negligible Impact on Soil Water in Nebraska Maize–Soybean Rotation

One perceived cost of integrating winter cover cropping in maize (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotation systems is the potential negative impact on soil water storage available for primary crop production. The objective of this 3-yr study was to evaluate the effects of winter cover crops on soil water storage and cover crop biomass production following no-till maize and soybean rotations. Locations were near Brule (west-central), Clay Center (south-central), Concord (northeast), and Mead (east-central), NE. Treatments included crop residue only (no cover crop) and a multi-species cover crop mix, both broadcast-seeded before primary crop harvest and drilled following harvest. Pre-harvest broadcast-seeded cereal rye (Secale cereale L.) was also included in the last year of the study because rye was observed to be the dominant component of the mix in spring biomass samples. Soil water content was monitored using neutron probe or gravimetric techniques. Mean aboveground cover crop biomass ranged from practically 0 to ~3,200 kg ha–1 across locations and cover crop treatments. Differences in the change in soil water storage between autumn and spring among treatments occurred in 4 of 20 location–rotation phase–years for the top 0.3 m of soil and 3 of 20 location–rotation phase–years for the 1.2-m soil profile. However, these differences were small (profile). In conclusion, winter cover crops did not have an effect on soil water content that would impact maize and soybean crop production

Introducing green manures in an organic soybean-winter wheat-corn rotation: Effects on crop yields, soil nitrate, and weeds

In organic soybean– winter wheat – corn rotations, animal manure is a common choice to maintain high yields, but leguminous crops grown as green manures after wheat harvest and incorporated into the soil before corn planting, can be an alternative when animal manure is not accessible. Forage legumes with high dry matter (DM) production and high biological N fixation have been shown to meet corn N demand. However, in Eastern Nebraska, lack of precipitation can reduce green manure growth and N fixation, leading to an insufficient N supply for corn, but corn growth can also be impacted by green manure soil water use. Our objectives were 1) to determine the green manure potential of four forage legumes, and 2) to evaluate management methods that optimize green manure benefits. We conducted an experiment at the ARDC near Mead, NE, from 2011 - 2014. Red clover, white clover, alfalfa, and sweet clover were undersown into winter wheat in early spring. After wheat harvest, they were either mowed or not mowed, and terminated in the fall or the next spring. We measured green manure DM, weed DM, soil nitrate concentrations, and crop yields throughout the rotation. We compared green manure effects to effects of cattle manure, post-wheat soybean green manure, and a control (no fertilizer). Red clover produced the most DM, up to 5.5 Mg ha-1 and showed excellent weed control, especially when mowed. Green manures did not increase soil N compared to the control. Corn yields were always significantly higher after cattle manure (7.6 to 8.1 Mg ha-1) than after undersown green manures, and were lowest after red clover in 2012 (2.8 Mg ha-1) and after white clover in 2013 (4.6 Mg ha-1), because of the clovers’ high soil water use and insufficient N production. In our study, green manures established well, but increased corn yields compared to a control in only one of three years. Cattle manure was the most reliable method to maintain high crop yields. Future research should investigate combinations of cattle and green manure to increase N availability to corn and decrease N leaching losses after corn harvest. Advisor: James R. Brandl

Seeding Rates and Productivity of Broadcast Interseeded Cover Crops

Broadcast interseeding cover crops into corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) instead of drill-planting after harvest extends the cover crop season and improves productivity, but establishment can be insufficient. Our objectives were to find broadcast seeding rates that result in maximum spring biomass and N uptake. We tested cereal rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth) in south-central and eastern Nebraska in 2016–2017 and 2017–2018. Seeding rates for rye were 341, 512, and 682 seeds·m−2, and 119, 178, and 238 seeds·m−2 for vetch. We broadcast in late September and terminated by early May. Fall emergence was between 3 and 54% of broadcast seeds, and greater for vetch. When broadcast into corn, rye spring biomass was 1472 kg·ha−1 with N uptake −1 −1−1 of 38 kg·ha . Vetch biomass was 361 kg·ha with 13 kg·ha N uptake. In soybean, rye produced −1 −1 −1 −1 2318 kg·ha with 59 kg N·ha and vetch produced 535 kg·ha with 21 kg N·ha . Higher seeding rates increased biomass and N uptake only for rye broadcast into corn. Year and site effects and possibly differences in main crops influenced cover crop productivity

Science-Based Organic Farming 2006: Toward Local and Secure Food Systems

Organic farming includes growing food and fiber — animals, agronomic crops, horticultural fruits and vegetables, related products — as one dynamic and rapidly evolving component of our complex U.S. food system. Even as more farmers are moving toward organic certification and participation in an environmentally sound and economically lucrative market, questions arise about the long-term social impacts and sustainability of a set of practices that has gone from a movement to an industry. Consolidations in the organic trade have brought multinational corporations to the table, as they have observed a grassroots activity that has grown by 20% per year for the past two decades, and that now includes a segment of the food system that has over $11 billion in annual sales in the U.S. alone. The quest is broadening in our search for local and secure food systems. Beyond the threats of terrorism, insecurity of long supply lines, and dependence of a global food chain on inexpensive fossil fuels, there is growing concern about how food can be produced locally. This implies local ownership and management, use of foods that are in season, promotion of closed materials cycles, and distribution of benefits from the food system in ways that the current organic certification system cannot assure. In this set of resource materials for 2006, we present organic farming in the context of family operations, environmental soundness, and social accountability. Why do farmers convert to organic production, and what is its future? Why are local food security and connecting people to their food supply important? Are these idealistic questions that have no connection to “science-based organic farming” or do they help open a rich and productive discussion about the whole future of our food system? Here we present publications about production practices for organic crops and animals, about processing and marketing, and about the certification process. But we also open the debate about the future of organic farming, and what some alternatives might be that can enhance the future of family farming and locally secure food systems. There is a fine line between education and advocacy, and we attempt at every turn to identify what is established through science and where opinion enters in. To assume that science is value free is a myth, yet we introduce ethics, philosophy, and social values into this discussion to provoke further discussion and hopefully promote progress in establishing a long-term, sustainable, and equitable food system

Seeding Rates and Productivity of Broadcast Interseeded Cover Crops

Broadcast interseeding cover crops into corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) instead of drill-planting after harvest extends the cover crop season and improves productivity, but establishment can be insufficient. Our objectives were to find broadcast seeding rates that result in maximum spring biomass and N uptake. We tested cereal rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth) in south-central and eastern Nebraska in 2016–2017 and 2017–2018. Seeding rates for rye were 341, 512, and 682 seeds∙m−2, and 119, 178, and 238 seeds∙m−2 for vetch. We broadcast in late September and terminated by early May. Fall emergence was between 3 and 54% of broadcast seeds, and greater for vetch. When broadcast into corn, rye spring biomass was 1472 kg∙ha−1 with N uptake of 38 kg∙ha−1. Vetch biomass was 361 kg∙ha−1 with 13 kg∙ha−1 N uptake. In soybean, rye produced 2318 kg∙ha−1 with 59 kg N∙ha−1 and vetch produced 535 kg∙ha−1 with 21 kg N∙ha−1. Higher seeding rates increased biomass and N uptake only for rye broadcast into corn. Year and site effects and possibly differences in main crops influenced cover crop productivity

Cover Crops: A Primer

When deciding how best to use cover crops, it is important to consider the ultimate goal. Is it to increase soil organic matter, increase nutrient availability to subsequent crops, reduce soil compaction, supply forage for livestock, and/or suppress weeds? Answering these questions will help identify the cover crops that offer the best chance of success for meeting the goal. Primarily, cover crops are used to enhance soil conservation, nutrient cycling and supply, and weed control. However, these benefits vary based on the species of cover crop that is planted, so it is important to select the crop type that will fit into your current cropping system, as well as provide the desired outcome. It is important to note that yield decreases to the subsequent commodity crop have sometimes been observed with the use of cover crops, from incomplete termination, soil moisture loss, and/or nutrient immobilization. All of these can be minimized with proper selection and management of your cover crop

Is allelopathy from winter cover crops affecting row crops?

Cover crops (CC) have been explored in corn (Zea mays L.), cotton (Gossypium hirsutum L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.) systems for their allelopathic potential to control weeds. However, allelopathic compounds may negatively affect these row crops by reducing germination, emergence, and grain yields. We reviewed studies that document allelopathic effects of CC on subsequent row crops in field and laboratory settings. We summarize the influence of CC management, including biomass production, planting and termination timing on allelochemical quantity. Our review found few studies documenting allelopathic effects of CC on row crops in field settings. Studies that focus on understanding yield impacts of CC on row crops should be designed to include allelopathic CC–row crop interactions. Understanding the link between CC management and allelopathic dynamics can help avoid impacts on the growth and productivity of the subsequent row crop