Progress report for LNE23-476R
Project Information
This project will investigate the concept of strategic manipulation of row orientation (N-S vs. E-W) to improve climate adaptation and interseeded cover crop success in silage corn and soybeans in the Northeast. Row orientation modulates the amount of sunlight that reaches the interrows and subsequently influences soil moisture and the growth of plants between crop rows (weeds or cover crops). We hypothesize that optimal row orientation will differ in non-interseeded and interseeded systems. By providing more interrow shading, E-W orientation will lead to higher soil moisture, greater weed suppression, and higher yields under most conditions in the Northeast. Conversely, by allowing more light to reach the interrow, N-S orientation will lead to greater interseeded cover crop performance without negatively affecting crop yields, which will benefit from the soil shading of the interseeded cover crop. To test these hypotheses, we will conduct research across a latitudinal and environmental gradient in Pennsylvania, New Hampshire, and Vermont. Both research station and on-farm research will investigate the effects of row orientation on crop and cover crop performance in interseeded and non-interseeded systems and will elucidate mechanisms behind the observed results, including the effects of row orientation on light, soil moisture, and weed dynamics. Cover cropping in the Northeast is rapidly expanding, but is implemented on <20% of annual crop acres in the three states where research will be conducted. Farmers have expressed interest in interseeding as a way to expand the diversity of cover crop species that can be grown in short growing seasons, but have reservations about inconsistent performance of interseeding. This project will provide critical data on how intentional row orientation can be used to reduce variability in interseeded cover crop performance, eliminating some of the barriers to adopting the practice. In addition, it will provide data on a free climate adaptive practice on acreage that is not interseeded. This makes the project unique in that it meets farmers “where they are” with respect to climate adaptation. Farmers will be engaged throughout the project with interactive field days and demonstrations, and on-farm research trials in the third year of the project.
Strategic manipulation of crop row orientation (N-S vs. E-W) holds promise as a way to enhance interseeded cover crop performance and as a standalone practice to conserve soil moisture and suppress weeds, but it has not been systematically investigated. The objective of this project is to quantify the effects of row orientation on yields, soil moisture, light, weeds, and interseeded cover crops in silage corn and soybean systems. Our research has potential to improve the reliability and therefore adoption of interseeded cover crops while also providing a climate adaptive technique on acreage where interseeding is not practiced.
Intentionally orienting crop rows N-S or E-W is not widely recognized by farmers and researchers as a climate adaptive practice [1, 2]. This is a missed opportunity for farmers, as compelling evidence (reviewed below) suggests that strategic manipulation of sunlight by deliberately orienting crop rows could contribute to the resilience of agriculture in the Northeast (and to Northeast SARE’s outcome statement) in multiple ways. First, it could improve the reliability and performance of interseeding—a practice that is rapidly gaining interest as a way for farmers to diversify and improve cover cropping, but which some farmers hesitate to adopt because of inconsistent results. Second, it could buffer against increasingly common moisture-limiting conditions on the more than 80% of annual agricultural acres where cover crops are not used (with the exception of Maryland and Delaware, where adoption is higher). Finally, intentional row orientation shows promise as a non-chemical weed suppressive strategy. All of these benefits come at zero cost.
The evidence behind these assertions is both theoretical and empirical. The theory is simple: in summer, N-S orientation leads to greater sunlight reaching the interrow during the mid-day period while temperatures are highest, while E-W orientation leads to more shading of the interrow area during this period [3, 4]. This suggests that N-S orientation could improve the performance of interseeded cover crops since light is often the most limiting resource as interseeded cover crops get established under a rapidly closing crop canopy. Before his retirement, Penn State scientist Dr. Bill Curran quantified the effect of row orientation on cover crops interseeded into corn at a single site in Pennsylvania and found that a N-S orientation led to 62% higher annual ryegrass biomass in October than E-W (P=0.004; unpublished data); however, additional data are needed to determine the generality of these conclusions across environmental gradients. Conversely, in the absence of interseeded cover crops, N-S orientation allows greater light infiltration, promoting weed growth [5]and increasing evaporation from the soil surface leading to higher moisture stress for crops [6, 7] and . Given the increasing frequency of summer drought in the Northeast [8], this suggests E-W orientation may be optimal in the absence of interseeded cover crops.
Across the Northeast, there are nearly 13,000 farms growing over a million acres of silage corn. Less than 1% is irrigated, demonstrating that soil moisture-conserving practices are paramount. Silage corn systems have seen a dramatic uptick in cover cropping nationally, from <15% in 2012 to nearly 25% of acreage in 2017. There are over 13,000 farms growing 1.6 million acres of soybeans in the Northeast and 6% is irrigated. Cover crop use in soybeans is less common at 10% [9]. Current row orientation of these acres is unknown, as is the percentage of acres where topography restricts crop orientation. Nonetheless, it is fair to assume that there are tens or hundreds of thousands of acres of corn and soybeans in the Northeast to which intentional row orientation could be immediately and freely implemented.
Research
- In the absence of an interseeded cover crop, E-W orientation will lead to higher yields in the majority of sites and years in the Northeast because of increased soil moisture and weed suppression due to shading.
- In the presence of an interseeded cover crop, N-S orientation will:
- Lead to higher cover crop biomass.
- Have limited effect on crop yield because interseeded cover will conserve soil moisture and suppress weeds.
- Increase flexibility for timing of interseeding compared to E-W because of greater light availability for before canopy closure.
- Cover crop response to row orientation will be species’ specific.
We conducted replicated field trials in NH, VT, and PA in 2023-24 and 2024-25 (ongoing). Each site had four blocks (replications). At each site, upright or semi-upright silage corn varieties were planted in main plots of N-S and E-W orientations at a population of 30,000/acre. Within these main plots, sub-plots of interseeding treatments were planted at approximately V4-V6 using the Penn State Interseeder (modified grain drill). Treatments included: weedy control, interseeded winter rye (150 lb/acre), and interseeded mix of annual ryegrass, crimson clover, red clover, and radish (35 lb/acre). A “conventional winter rye” treatment (150 lb/acre) was planted after silage harvest to represent the standard cover cropping practice. Weeds were managed using a burndown herbicide (glyphosate) prior to corn planting and again prior to interseeding. This represents a divergence from standard practice in that the herbicide application prior to interseeding did not include pre-emergent herbicides, which have been shown to interfere with cover crop establishment.
Data collection included silage yields, weed and cover crop biomass at silage harvest (September), prior to a hard freeze (November) and again the following spring (April-May). Surface soil temperature was logged in all sites during silage growth. In 2023, photosynthetically active radiation (PAR) was measured between the corn rows using a hand held meter at two time points. In 2024, at UNH only, PAR meters were installed in all four blocks, logging PAR in the understory of corn every minute in N-S and E-W orientations to provide insight into the light dynamics affecting cover crop and weed growth.
Plans for continued experiment station research are under discussion and will be decided by the researchers and advisory panel after a close look at the results. On farm experiments will take place in the third year of the project (2025), the design of which will be decided following further discussion and analysis of results.
Initial data analysis indicates that row orientation had effects on silage yields, weeds, and cover crops in more than half of the site years (total of six site years). However, the results were not consistent and require further investigation to determine potential mechanisms. The PAR data gathered at UNH in 2024 showed that understory light is strongly influenced by row orientation and seasonality. The robust dataset from these multiple site years should allow us to glean insights into how row orientation interacts with climate and soils to influence crop yields, cover crops, and weeds and how intentional manipulation of row orientation may (or may not) be a tool for climate adaptation either by itself or by facilitating more robust cover cropping practices.
Education & Outreach Activities and Participation Summary
Educational activities:
Participation Summary:
Carolyn Lowry shared our experiment station research in Pennsylvania during a Penn State Interseeding workshop with farmers. This event was synergistic with other interseeding outreach.
Heather Darby shared the experiment station research for this project during the Borderview Farm field day in Vermont in 2023 and 2024.
UNH Farm Services Manager Peter Davis included an overview of this project in the annual corn and forage meeting for New Hampshire farmers sponsored by UNH Extension.
The majority of outreach will occur in the final, third year of the project (2025) as originally planned.
Learning Outcomes
We have not collected any data in this area as we are in the first year of our project.