seeding – Maryland Agronomy News

Evaluating Drone-Seeded Cover Crops

Erika Crowl and Andrew Kness
University of Maryland Extension

Recent interest has been generated in using drones to seed cover crops into agronomic crops in small, irregularly shaped fields with rolling terrain or those fields otherwise not suitable for aerial seeding using a fixed-wing aircraft or helicopter. However, little is known about how effective drones are at seeding cover crops and if they can deliver seed at the appropriate rate to establish a sufficient cover crop. In order to evaluate cover crop stand establishment seeded via drones, we conducted an on-farm trial with support from the Maryland Soybean Board.

A cover crop of radish was flown on to a 26 acre standing corn field in Baltimore County, MD on August 27, 2020 at the rate of 16 pounds of pure live seed per acre using a HSE-TTA drone equipped with a spin spreader capable of carrying 40 lbs of seed. The field was an excellent candidate for this trial because of its irregular shape, rolling terrain, and close proximity to power lines and wood lines (Figure 1). Corn grain was harvested on September 15, 2020 and cover crop establishment was measured on October 21, 2020 by counting the number of radish plants per square foot in a one square foot area at 20 random locations across the field. The average cover crop plant population in the field was 3.1 plants/ft², with a minimum of 0 and maximum of 6. Radish plants averaged 5 inches in height at the time of rating.

field seeded with radish cover crop — Figure 1. Field location of drone-seeded cover crop (outlined in red). Image: Google Maps (bottom).

Canopy density was calculated using the Canopeo^© application for smartphones (Oklahoma State University Department of Plant and Soil Sciences, Stillwater, OK; www.canopeoapp.com). Images were captured at 20 random locations across the field at a height of 2.5 feet above the ground and percentage green canopy was calculated by the Canopeo software (Figure 2). Average canopy coverage was 39.1%, with a minimum and maximum value of 20.3 and 53%, respectively.

Aerial establishment of cover crops is heavily influenced by soil moisture availability. August and early September saw sufficient rainfall in the region, contributing to conducive conditions for cover crop establishment. These data, representing only one field and one environment, demonstrate the potential that aerial seeding a radish cover crop with drones may be an effective method for establishing cover crops in these challenging fields. Future work will be done to replicate and gather additional data so that we can fully understand the feasibility of seeding cover crops with drones.

Acknowledgements: We would like to thank A-1 Aerials, K Drone Services, Graystone Farm, and the Maryland Soybean Board for supporting this work.

Key Steps for Optimum Forage Establishment

Amanda Grev, Pasture & Forage Specialist
University of Maryland Extension

Last month we discussed strategies for assessing pasture stands and some initial considerations when beginning to think about pasture renovations. Now that August has arrived, if you have decided to proceed with some form of pasture renovation this fall it will soon be time for planting. Regardless of the extent of your renovation, there are several steps you should follow to make sure the seeding process goes smoothly. Below is an overview of the key steps necessary for optimum forage establishment.

Step 1: Correct Soil Fertility

Poor soil fertility is one of the most common causes of poor stand establishment and also poor stand persistence over time. Acidic conditions (low soil pH) will reduce nutrient availability and impair root growth and development, and essential nutrients like phosphorus are critical for proper seedling development. Because of these effects on plant nutrient availability and utilization, ensuring adequate soil pH and fertility is essential for optimum stand establishment and to obtain persistent, high-yielding stands long term. Soil fertility testing should be done prior to renovation so that lime and fertilizer can be applied according to soil test recommendations.

Step 2: Control Weeds

Weeds compete with desirable forages for light, nutrients, moisture, and space and can shade out or outcompete new seedlings. For best results, ensure weeds are controlled prior to seeding. Remember that while herbicides can be a useful tool for weed management, they are not the only option for weed control. An integrated approach that combines various cultural, mechanical, and chemical control practices will be the most successful.

Step 3: Select Adapted Species

Not all forages will perform equally on different sites, so be sure to select forages that are well suited for your soil and site characteristics. This includes variables such as soil type, drainage, moisture holding capacity, pH, fertility, and topography. For example, species such as orchardgrass or alfalfa require a higher level of fertility and will not thrive in systems with low soil pH or poor soil fertility. Be sure to select forage species that will match your intended use (hay vs. pasture, perennial vs. annual, time of year, management system) and livestock requirements based on species, age, and life stage.

Step 4: Inoculate Legume Seeds

If you plan to incorporate a legume as part of your forage mix, be sure the seed is properly inoculated with nitrogen-fixing bacteria. Some legume seeds come pre-inoculated, which saves time and helps to ensure inoculation. If not, be sure to select the appropriate inoculant strain depending on the legume species and inoculate the seed with fresh inoculant prior to seeding using an effective adhesive material to hold the inoculant on the seed. Inoculants are living organisms and will only work if the bacteria are alive when applied, so be sure to use proper storage and handling and check expiration dates.

Step 5: Graze and/or Clip Close

Grazing or clipping a pasture close to ground level prior to seeding will help eliminate residue and assist in suppressing competition from existing vegetation, giving new seedlings an opportunity to grow. If using livestock to accomplish this via grazing, be mindful of the potential effects this may have on animal performance, including the consumption of lower quality forage and/or the potential for increased parasite loads as animals graze below the usual minimum height recommendation.

Step 6: Prepare a Proper Seedbed

This step will vary slightly depending on the use of tilled vs. no-till seedings. If using tillage, be sure the seedbed is soft yet firm following tillage. An underworked seedbed will have too much surface residue and will be too rough for good seed placement, while an overworked seedbed will be too fluffy and fine and will dry out quickly. A good rule of thumb is that your boot tracks should be around ¼ inch deep. For no-till seedings, it is especially important to suppress the existing stand and reduce residue prior to planting. In addition to close grazing and/or clipping, the existing stand can be suppressed using a nonselective herbicide.

Step 7: Seed at the Proper Depth

Seeding too deep is one of the most common causes behind establishment failures. Be sure the seed drill is calibrated appropriately so that seed is placed at the proper depth. Take into account your soil type, texture, and moisture conditions; in general, seed should be placed slightly shallower in a heavier soil with a higher moisture content and slightly deeper in a lighter soil with lower moisture content. For most cool-season forages, the ideal seeding depth is ¼ to ½ inch, but seed characteristics vary so be sure to determine the optimum depth and adjust accordingly prior to planting. The key is to provide good seed to soil contact without placing the seed too deep.

Step 8: Seed at the Proper Time

Cool-season forages can be seeded in either the spring or late summer. Advantages of late summer seedings generally include reduced weed competition and cooler weather conditions during establishment. The ideal time will vary depending on your location and weather conditions but in general, the optimum time for late summer seeding in Maryland occurs from mid-August through mid-September.

Step 9: Seed at the Proper Rate

Similar to seed depth, calibration is essential to achieve a proper seeding rate. Seeding rates will vary based on forage species selection, be sure to follow recommendations when making seeding rate decisions. Pasture seeding rates are typically higher than hay seeding rates to provide a denser sod for grazing. Seeding rates can be adjusted slightly based on conditions at the time of seeding. If conditions are optimum, seed at the lower end of the recommended range. If conditions are poor, seed at the higher end of the recommended range.

Step 10: Manage New Seedings During Establishment

New seedings are especially sensitive during their establishment year. To maximize success, delay grazing on newly seeded areas until sufficient root systems have been developed to prevent livestock from uprooting newly established plants when grazed. Avoid grazing new stands during extremely wet periods, be very careful not to overgraze, and continue to scout for weeds or other potential issues that can impair establishment.

Effects of Planting Population on Yield in Full Season Soybeans

Kelly Nichols, Agriculture Agent Associate & Matt Morris, Agriculture Agent
University of Maryland Extension, Frederick County

Soybean population plots were planted on two farms in Frederick County near Thurmont and Tuscarora on June 4 and 7, respectively. Planted populations were 80, 100, 120, 140, and 160 thousand plants per acre (ppa). The Thurmont plots were planted on 30-inch spacing with three replications. The Tuscarora plots were drilled on 7.5-inch spacing with four replications.

On July 1, initial population counts were taken at both farms. At the Thurmont farm, plots ranged from 79 to 88 percent germination. At the Tuscarora farm, plots ranged from 88 to 98 percent germination (Table 1). This is consistent with the germination percentage of the seed.

Plots were harvested on October 3 and October 24 at the Tuscarora and Thurmont farms, respectively. The average yield for each farm individually and combined were calculated (Table 2). Yield ranged from 61 to 70 bu/A. Overall, yield differences between the populations were within three bu/A. While a complete statistical analysis has not been conducted, the trend of the data indicates that planting at a lower population, such as 120,000 or 100,000, would allow for reduced seed costs while still maintaining optimum yield.

The variety used at the Thurmont farm was Pioneer P37A69, which retails for $71.00 per unit of 140,000 seeds. The variety used at the Tuscarora farm was Hubner 38-27R2X, which retails for $59.00 per unit of 140,000 seeds. (Note that these costs do not include any discounts or seed treatments.) At the time of harvest, soybeans were $9.51/bu on the Chicago Board. The net dollar amount was calculated by subtracting the seed cost from the gross amount per acre. At the Thurmont farm, the 100,000 planting population had the highest net per acre at $598.19, while the 140,000 and 160,000 populations had the lowest net, around $581/A (Table 2). At the Tuscarora farm, the 120,000 planting population had the highest net per acre at $560.13, while the 160,000 population had the lowest net at $515.76/A.

Planting at lower populations, around 100 to 120 thousand ppa, may not reduce yield or net per acre, indicating that this is a potential for cost savings on farms. We are planning to conduct this study again next year at more locations around the state. To stay up to date with this research project, visit https://go.umd.edu/FCagresearch.

Table 1. Initial Population Counts, July 1.

	Thurmont Farm		Tuscarora Farm
Planted Population (1000 plants per acre [ppa])	Initial Population (1000 ppa)	% Germination	Initial Population (1000 ppa)	% Germination
80	63	79	71	88
100	85	85	88	88
120	95	79	117	98
140	123	88	124	88
160	135	84	153	96

Table 2. Average Yield at 13.5% Moisture and Net Profit in $/A.

	Yield (bu/A)			Net $/A
Planted Population (1000 plants per acre)	Thurmont Farm	Tuscarora Farm	Both Farms	Thurmont Farm	Tuscarora Farm
80	67	61	64	596.92	548.18
100	68	63	65	598.19	554.78
120	69	64	66	595.33	560.13
140	69	63	66	581.39	542.89
160	70	61	65	581.71	515.76

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