Evaluating the use of forage radishes as a pasture improvement tool

Evaluating the use of forage radishes as a pasture improvement tool

Summary

Forage radishes have been used to break up soil compaction in row crops. In this project I am investigating the physical and chemical changes that occur as a result of forage radish roots growing in non-till pasture. Typically forage radishes (Raphanus sativus) are sown between June 15 and July 15 so that the above ground growth can be grazed by cattle. In the winter radishes are killed by frost and decompose quickly in the spring. In row-crop systems, radish residues will be mixed with compacted soil during tillage eliminating holes. In no-till pasture radish holes would have to be filled in by redistribution of surface materials. I am interested in seeing what effects radish roots have on soil organic matter, soil density at the root level and how infiltration and runoff rates at the field level are affected by the ephemeral presence of radishes in the pasture. A sandy loam pasture soil was sown with radish in early July, 2012 at a seeding density of 8000 seeds per acre and allowed to grow for 12 weeks. Prior to grazing soil core samples were taken at 0, 10, and 30 cm radiating from the FR root to a depth of 20 cm. We also sampled earthworms near the radishes and in a control paddock without radishes. Soil organic matter was greater at the surface than at the lower depth. It was greater near the root than away from the root. At the soil surface density was lower near the root, an unexpected finding, and greater further away. Infiltration measurements will be conducted in the spring and summer 2013.

Objectives/Performance Targets

1. Quantify the effects of forage radish growth and decomposition on a variety of soil quality indicators.

Soil core samples were taken at 0, 10 and 30 cm to a depth of 20 cm radiating from the forage radish (FR) root and soil cores were also taken from an untreated control plot (CP). Earthworms (EW) were sampled by the removal of soil from 30X30X30 cm cube of soils. Earthworms were collected by hand sorting and were identified to ecological group by morphological and pigment characters. Analysis of the cores was performed in the lab at UVM. The core samples revealed that at the soil surface density was lower adjacent to the root (0.78 g/cm3) than at 30 cm (0.92 g/cm3) from it, but there was no difference among distances for the 10 – 20 cm depth increment (1.3 g/cm3). Similarly, organic matter differed only at the surface between the 0 (11%) and 30 cm (9%) distance. There was no significant difference in dry root mass among distances from the root and soil depth. Earthworm density was greater near radish roots.

Issues with weighing fresh samples accordingly prevented accurate estimation of soil moisture in the fall of 2012; unfortunately soil moisture was not measured in the fall, but will be performed in the spring and throughout the 2013 season and compared between plots.

2. Assess the impact of forage radish on forage production and quality.

This survey will be conducted on the paddocks in the summer 2013.

3. Monitor impacts of forage radish growth and decomposition on soil infiltration rates.

This part of the experiment will be conducted in the Spring and Summer of 2013 with a Cornell Sprinkler Infiltrometer which has already been purchased.

4. Use experimental results to develop and distribute relevant and appropriate fact sheets for use by farmers and agricultural professionals describing how to utilize forage radishes in pastures and the possible advantages of doing so.

I will begin this task when first infiltration and forage mass measurements have been collected in 2013. As soil quality indicators show potential benefits toward soil health I will be able to directly assess the benefits of the use of forage radishes; in cooperation with the Center for Sustainable Agriculture and the Gund Institute for Ecological Economics I will develop an applicable cost-benefit analysis for farmers taking into count soil type, farm size, and herd size.

• Control left- Radish right
• Soil core samples from 0, 10, and 30 cm

Accomplishments/Milestones

An ungrazed pasture with a sandy loam soil in High Gate Center, VT was seeded with forage radish at a seeding density of 8000 seeds per acre in early July, 2012. The plot remained ungrazed during the initial growth period and soil core samples as well as earthworm samples were taken on October 17, 2012. I performed lab analysis of soil organic matter, bulk density, volumetric water content and dry root weight during October and November. Data analysis is currently ongoing. I will be trained to perform additional lab procedures for active carbon and nitrogen extraction at UVM and will be finalizing the lab work shortly along with the respective data analysis. I concluded that in the fall 2012, 12 weeks after sowing, there were differences in the spatial distribution of soil properties as a function of distance from radish roots.

In the spring and summer, more core samples will be taken as before on the FR and the CP plots to be analyzed again for soil quality indicators. However, we will also analyze infiltration rates and forage growth at that point. As the FR root decomposes, continuous samples will be taken over time to assess the impact of the FR root on soil quality indicators, infiltration rates, and forage quality. Continuing beyond spring 2013, data analysis will be performed and compared to the fall 2012 results along with the control throughout the 2013 season. Fact sheets and economic assessment will be prepared in the summer and fall 2013.

Impacts and Contributions/Outcomes

To date I have analyzed soil cores and the distribution of soil properties around FR roots. These data and information to be generated next year will be included in a factsheet to be distributed through the NE Pasture Network and a peer-reviewed paper.

Collaborators: