Effects of Different Cereal Rye and Winter Camelina Seeding Rates on Biomass Production and Soil Properties When Broadcast Seeded

Methods

Benefits to soil health generally increase as cover crop biomass production increases. This study sought to determine how seeding rate of two cover crop species and mixtures affected biomass production and some soil health indicators. The objective was to see how much biomass was produced when two cover crops species and mixtures were seeded at different rates and see how the different seeding rates and mixtures affected soil health indicators. This study was conducted at 3 locations. One location was by Spring Green, Wisconsin, another by Clear Lake, South Dakota and the last by Beresford, South Dakota. The soil texture at the Spring Green site was sand, Clear Lake was clay loam and Beresford was silty clay loam. At the Spring Green site the cover crop was broadcast onto fallow land that was disked prior to when the cover crop was broadcast. At the Beresford and Clear Lake site the cover crop was broadcast into standing corn at R4-R6 stage. At the Spring Green site camelina was not planted and biomass was not clipped from the rye + red clover and rye + red clover + classic trio mix plots in spring of 2025. The cover crop was planted on August 3rd 2024 at the Spring Green Site, August 30th at the Clear Lake site and September 5th at the Beresford Site. There were four replicates of each treatment planted. Rye was seeded at 25, 50, 75 and 100 lbs per acre and in a mixture with red clover (rye at 25 lbs/ acre and red clover at 4 lbs/ acre) and rye + red clover+ classic trio mixture (rye at 25 lbs/ acre, red clover at 2 lbs per acre and classic trio at 2 lbs/ acre). The classic trio mixture was 40% radish, 30% rapeseed and 30 % turnip. The rye and rye mixtures were spread using a broadcast lawn fertilizer spreader. Camelina was broadcast at 5 and 10 lbs/ acre by hand. The cover crop biomass was clipped on April 30th at the Beresford Site, May 2nd at Clear Lake site and May 25th at the Spring Green site. Soils were sampled at the same time the cover crop biomass was clipped prior to being terminated. Soil water content was determined on samples collected from the 0-6 and 6-24 in depth at the Beresford and Spring Green site and only from the 0-6 in depth at the Clear Lake site due to wet soil conditions when sampling. Also, soil samples were collected from the 0-3 in depth and organic matter, particulate organic matter, dry aggregate size distribution and percent water stable aggregates was measured on these samples. If the percent water stable soil aggregates is closer to 100 % the soil is likely to stay together when wet by rainfall or irrigation but if its closer to 0 the structure is more likely to fall apart and the soil is more susceptible to water erosion. Generally if the average diameter of dry soil aggregates is higher the soil is less likely to blow away from high winds. Soil available nitrogen will be measured at a later date. In addition, penetration resistance was measured as an indication of soil compaction for the 0-3 and 3-6 in depth. A lower penetration resistance means that the soil is not compacted and roots can easily penetrate through it. Also, time for 1 in and a 2nd inch of water to infiltrate was determined.

Results

Climate

There was a weather station at the SDSU Southeast Research Farm (Beresford). However, data for the Clear Lake site is from the SDSU Mesonet Oak Lake Research Station and data for Spring Green is from the Lone Rock Wisconsin Airport which were closest available weather stations with data posted online (National Weather Service 2025; South Dakota Mesonet 2025). Although they are not at the exact location, they give an indication of how much precipitation was received in the area. Monthly precipitation received during the time that cover crops were growing is shown in Table 1.

At the initiation of the study the water content was 0.05 lb/lb in the 0-6 and 6-12 in depth at the Spring Green Site, 0.26 lb/lb at the Clear Lake site in the 0-6 and 6-12 in depth and was 0.16 lb/lb in the 0-6 in and 0.19 lb/lb in the 6-12 in depth at Beresford when the cover crop was planted. Precipitation data is included in table 1 to show that in Fall 2025 little precipitation was received to establish the cover crop at two of the sites and it did not germinate until spring 2025 at the Clear Lake and Beresford sites. Photos of the cover crops are shown in Figures 3-7 in the next section of this article.

Figure 1. Fall biomass production from the different cover crop seeding rates and mixtures at the Spring Green Site RC is red clover and BR is classic trio mixture consisting of radish turnip and rapeseed.

The cover crop did not germinate in Fall 2024 at the Beresford and Clear Lake sites featured in this study, so the fall biomass was not clipped. At the Spring Green site in this study, which received more precipitation, the cover crop did germinate and biomass was clipped on November 25, 2024.

This study found that adding the classic trio and red clover with the rye increased the cover crop biomass production by 80 to 100 pounds per acre compared to just planting the rye cover crop at any seeding rate (Figure 1).

In spring of 2025 there appeared to be little clover growing in the rye and red clover plots at the Spring Green Site. Biomass clipped in the no cover crop plot at Spring Green was mostly weeds. Rye seeding rate did not affect spring biomass production at the Spring Green site. (Figure 2).

Figure 2. Spring biomass production of cover crop seeding rates and mixes at 3 locations. RC = red clover; WC = winter camelina; and BR = classic trio mixture of radish, turnip and rapeseed. Letters above columns indicate statistical differences at p=0.05

At the Beresford site rye was accidentally drill-seeded where the cover crop was planted. The no-cover crop plot biomass indicates how much biomass was produced from the drilled cover crop. The winter camelina, classic trio and red clover cover crops germinated poorly at Beresford with only an occasional small plant visible when walking through the plots. Among rye seeding rates there was no statistical difference in biomass production although the higher seeding rate did have a little higher biomass production (Figure 2). However, the winter camelina and no cover crop treatment did have lower biomass production compared to where rye was broadcast (Figure 2). Biomass production from the different cover crop mixtures ranged from 33 to 152 lbs/acre (Figure 2). The rye treatments at this site include the drilled rye plus the rye that was broadcast prior to harvest of the corn. Photos of rye planted at the different seeding rates at this site are in Figures 3-7.

At the Clear Lake site there was the lowest biomass production. The camelina germinated better than the rye cover crop in spring of 2025. Although there was no statistical differences the camelina plots produced a little more biomass compared to the rye cover crop or rye mixtures. However, average biomass production at this site was low (<60 lbs/ acre). It is worth noting that drilled rye cover crop only produced (92 lbs/acre) of biomass in the same field. A photo of the camelina planted at this site is shown in Figure 7.

Figure 7. Camelina cover crop planted at the Clear Lake site.

Soil Properties

Some soil properties were measured as indicators of soil health. Total organic matter was measured as an indication of soil health and is commonly measured in routine soil analysis. Generally, soils that have higher organic concentration have better soil health. Particulate organic matter is mostly organic matter added from plant roots and residues and should change more rapidly by management than total soil organic matter. At the initiation of the study the soil organic matter level was 5.8 % at the Beresford site, 7.1 % at the Clear Lake site and 1.4 % at the Spring Green site in the 0-6 in depth. Particulate organic matter was 0.68 % at the Beresford site, 0.98 % at the Clear Lake site and 0.81 % at the Beresford Site in the 0-6 in depth. Soil properties generally were not affected by the cover crop seeding rates or species (Tables 2-4). The only soil property that was affected by cover crops treatments was penetration resistance at the Beresford site (Table 2). Rye seeded at 50lbs or higher per acre had higher penetration resistance than no cover crop, rye in mixtures and camelina. However, the penetration resistance was much less than the 2 MPa (290 PSI) that can restrict root growth (Sinnett et al., 2008). Other soil properties were not affected by cover crop seeding rate or mixtures at the Beresford site (Table 2). At the Clear Lake and Spring Green site none of the soil properties were affected by cover cropping (Tables 3 and 4). Although there may appear to be differences in soil properties between treatments there was a lot of variability in the soil properties at the sites. It is worth noting that soil water content was not affected by cover cropping. Many producers are concerned about cover crops taking up water that could be available to the crop planted following the termination of the cover crop. Lack of change in soil properties is likely due to cover crops being planted for only one year and very low biomass production from the cover crop. To improve soil health cover crops need to produce significant biomass (>1000 lbs/acre) and or be planted for a long period of time. Having the cover crop add lots of carbon to the system (organic matter) is needed to improve soil health. The results of this study should be taken with caution as cover crops were only planted for 1 year and did not perform well.