The overall aim of the proposed research program is to provide information that may help change the mindset about cover crop management from one of doing the minimum to qualify for payments to managing for maximal cover crop benefits for soil health and profitability. Maryland has the nation’s highest proportion of cropland acres cover cropped. However, farmers enrolled in the state cover crop programs typically plant a single species cereal cover crop after cash crop harvest, which our research shows is usually too late to effectively capture the large pool of soluble nitrogen left deep in the soil or provide enough cover to adequately control overwinter erosion. Using aerial or ground based interseeding into standing crops, choosing earlier-maturing corn and soybean cultivars, and making other adjustments to the farming system may allow earlier cover crop establishment.

Many farmers also cut short cover crop growth potential in spring by terminating cover crops as early as possible, commonly in late March or early April. Such termination is too early to allow the cover crops to optimally promote soil health, water conservation and crop yield. Delaying spring cover crop termination until optimal cash crop planting time, especially planting green instead of killing cover crops two to four weeks ahead of planting, could allow both timely cash crop planting and extended cover crop growth. Potential benefits of greater cover crop biomass growth include short-term benefits such as greater nutrient cycling, better weed suppression, and more effective water-conserving in summer,
in addition to longer-term benefits of increased soil organic matter and biological activity. Preliminary experience suggests that planting into living cover crops may also save time and improve stands and gain additional weed suppression advantages.

The aforementioned cover cropping benefits and concerns are of particular relevancy to soybean production for several reasons. First, soybeans tend to leave a large amount of soluble N in the profile at the end of the season (possibly more than corn, Figure 2) and soybeans tend to be harvested later than corn. These factors combine to make early cover crop establishment in fall especially important for soybean systems. Second, soybeans, unlike corn, do not tend to respond adversely to the early shading and N immobilization that may be associated with planting into living high-biomass cover crops after extended growth in spring. Soybeans therefore stand to benefit from water-conservation, nutrient-cycling (K, S, Ca, Zn, B) and compaction alleviation effects of high springtime biomass cover crops.

Our objectives are to 1) document the impacts (benefits and/or problems) of planting earlier and killing later, and 2) develop and test strategies and technologies for (a) getting cover crops established earlier, including airplane seeding, early maturing crop cultivars, and inter-seeding with ground equipment and (b) letting them grow longer in spring (including planting green). Using replicated experiments on coastal plain soils at the University CMREC research farm and collaborating commercial farms in 2017-2019 we found dramatic increases in N capture and reductions in nitrate leaching in both winter and spring from planting cover crops just two weeks earlier in September. Biomass carbon added to soil and N fixed by legumes was 4 times greater with early May instead of early April termination. There was no drag on yields with either practice so long as a mixture with brassicas and/or legumes was planted. We currently have 2 sites long-term at the Beltsville CMREC research farm, each with early-planted rye, and rye-radish-clover mix cover crops and control plots in both corn and soybean residue. We plan to measure nitrate leaching, cover crop biomass and nutrient contents, soil water fluctuations and crop growth and yield in 2022. We plan to also study the impact of cover crop termination timing on slug damage to both soybeans and corn seedlings on a silty soil with restricted drainage and previous slug infestations. In summary, this project will generate important information on how to better use cover crops for improved soil quality, reduced crop stress, enhanced nutrient and carbon cycling and profitability.

The objectives are to determine the effects:
1) of early-established cover crops on cover crop performance as well as corn and soybean yields.
2) of timing of cover crop termination in spring on seedbed conditions, pests, soybean crop stands, and performance.
3) of grass and 3-way mix cover crops on N response by corn (to three rates of N).

There are currently single-species and mixed-species cover crops planted for this project on 3 sites (two sandy and one silty) with large, replicated plots on CMREC research farm. We propose to re-plant the cover crops in 2022 using the Penn State Interseeder multipurpose drill (now manufactured commercially by Interseeder Technologies, LLC, interseedertech.com) in corn after tasseling, and using a high-clearance air-seeder at leaf drop in soybean.

We plan to use these sites to measure:
• winter/spring nitrate leaching,
• spring cover crop growth,
• slug activity and crop damage in early spring
• corn yield response to three levels of N fertilizer,
• soybean crop response to three cover crop termination dates,

The field experiments with a corn-soybean rotation were established in spring 2020 on two sites, one with well-drained sandy soils and one with moderately to somewhat poorly drained silty clay loam soils. The main plots (corn v soybean) are split into three cover crop treatment subplots (none, rye, 3-way mix) and these subplots are split further into management sub-subplots. For cover crops going into soybean, the management sub-sub plot treatments are the time of cover crop termination: 3 weeks before, same day, or 1 week after soybean planting. For cover crops going into corn, the sub-sub plot treatments had N fertilizer rates at side dressing: 0, 75 or 150 lbs N/acre. These rates will be increased to 0, 90, and 180 lbs N/acre in 2022. 13

Cover crop biomass for fall 2021 has been sampled but at this writing, samples are in the drier so data is not yet available. Crop yields for both soybeans and corn measured by hand harvest were unaffected by the interseeding establishment of cover crops in 2020 and 2022.

Research questions to be addressed by one or more replicated trials on-farm and on-station:
1. How well do inter-seeded cereal and multi-species cover crops reduce nitrogen loss during the leaching season?
2. How do planting date and termination date interact for a rye or a 3-way (cereal-legumebrassica) cover crop in terms of cover crop biomass, spring soil fertility, summer soil moisture and soybean or corn crop yield?
3. What are the effects of the termination date and planting green into a 3-way mix cover crop on:
a. pollen resources for beneficial insects
b. planter operation and crop stand establishment
c. slug damage to crop seedlings
d. soil water supply and temperature during the growing season
e. weed pressure
f. crop yield
3. How do rye and 3-way mix cover crop affect the corn response to N fertilizer? Can N rates be adjusted for the cover crop effect?
4. Is there a combination of kill dates and cover crop types that can minimize slug damage to soybean and corn seedlings? How is this related to crop residue, soil temperature and moisture?

We will use our results along with information in the literature to help educate farmers about the advantages of longer cover crop growth in spring, along with strategies that have been successful in overcoming (or disproving) some of the issues of concern to some farmers such as soil moisture depletion, hair pinning cover crop residues, crop damage by slugs, nutrient immobilization, etc.

Update:

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Update:

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Update:

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LAY LANGUAGE SUMMARY OF 01 APRIL 2022 – 30 MARCH 2023 RESEARCH AND RESULTS
Planting Green: Extending the Growing Season to Get More Payback from Cover Crops
Maryland Soybean Board
Ray Weil
Dept. of Environmental Science and Technology
University of Maryland

The overall aim of the research project was to provide information that may help change the mindset about cover crop management from one of doing the minimum to qualify for State subsidy payments to managing for maximal cover crop benefits for soil health and profitability. Maryland has the nation’s highest proportion of cropland acres cover cropped. However, many farmers enrolled in the state cover crop programs typically plant a single species cereal cover crop after cash crop harvest, which our research shows is usually too late to effectively capture the large pool of soluble nitrogen left deep in the soil or provide enough cover to adequately control overwinter erosion. Using aerial or ground-based interseeding into standing crops, choosing earlier-maturing corn and soybean cultivars, and making other adjustments to the farming system may allow earlier cover crop establishment.

Many farmers also cut short cover crop growth potential in spring by terminating cover crops as early as possible, commonly in late March or early April. Such termination is too early to allow the cover crops to optimally promote soil health, water conservation, and, potentially, crop yield. Delaying spring cover crop termination until optimal cash crop planting time, especially planting green instead of killing cover crops two to four weeks before planting, could allow timely cash crop planting and extended cover crop growth. Potential benefits of greater cover crop biomass growth include short-term benefits such as greater nutrient cycling, better weed suppression, and more effective water-conserving mulch in summer, in addition to longer-term benefits of increased soil organic matter and biological activity. Preliminary experience suggests that planting into living cover crops may also save time, improve stands, and gain additional weed suppression advantages.

The aforementioned cover cropping benefits and concerns are of particular relevancy to soybean production for several reasons. First, soybeans tend to leave a large amount of soluble N in the profile at the end of the season (possibly more than corn, Figure 2) and soybeans tend to be harvested later than corn. These factors combine to make early cover crop establishment in fall especially important for soybean systems. Second, soybeans, unlike corn, do not tend to respond adversely to the early shading and N immobilization that may be associated with planting into living high-biomass cover crops after extended growth in spring. Soybeans, therefore, stand to benefit from water conservation, nutrient cycling (K, S, Ca, Zn, B), and compaction-alleviation effects of high springtime biomass cover crops.

Our objective was to document the impacts (benefits and/or problems) of using cover crops and letting them grow longer in spring, including planting green into standing living cover crops. We conducted replicated experiments at two sites with contrasting coastal plain soils at the University Beltsville CMREC research farm. Each site had early-planted cover crop plots (rye cover crop and rye-radish-clover mix cover crop) and no cover crop control plots in both corn and soybean residue. We found large increases in biomass carbon added to soil and N fixed by legumes was 2 to 4 times greater with early or mid-May instead of early April termination. There was no drag on soybean or corn yields with either practice so long as a mixture with brassicas and/or legumes was planted.

We also studied the impact of cover crop termination timing on slug damage to both soybeans and corn seedlings on slug-infested silty soil with restricted drainage. Slug numbers and damage to soybeans were moderate this year and the same whether cover crops were used and planted green or not. We observed slugs feeding on the still-living cover crop tissue when soybean seedlings emerged in the late-kill planted-green treatments.

The use of the two cover crops did not generally reduce crop stand density achieved, even when planting green. The only slight, but statistically significant stand reduction was for soybeans planted into the dead residue of the early-killed 3-species cover crop mix, which may have been an allelopathic effect of short-lived toxins produced by the decomposition of those residues.

Soybean yields were relatively high (58 bu/acre average) and unaffected by cover crop treatments. Corn yields, in contrast, were relatively low in 2022, but significantly increased by the cover crops, especially the 3-species mix. In summary, this project generated important information on how to better use cover crops for improved soil quality, reduced crop stress, enhanced nutrient and carbon cycling, and profitability.