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Evaluating Compost Benefits in Alfalfa Hay for Improved Soil Structure & Fertility

We all recognize human health as a goal, but healthy soils is a key goal for farming operations, since healthy soils frequently result in higher yields and economic returns over time.  “Health” is often defined with a range of properties including high fertility, good water-holding capacity and drainage, long-term productivity, and sustaining organic matter content.

A joint UC Davis and UC Cooperative Extension research project was recently awarded funding for $250,000 from the California Department of Agriculture Healthy Soils Program, to look at the application of compost to alfalfa to improve soil structure and fertility. This grant is designed to fund implementation and demonstration of on-farm soil health practices that reduce greenhouse gas emissions and store carbon.

The recipients are Kate Scow and Radomir Schmidt, UC Davis Department Land, Air, Water Resources and UCCE advisors Michelle Leinfelder-Miles and Rachael Long, in collaboration with Westside Spreading LLC.

This project will demonstrate compost application to alfalfa for improving soil structure and fertility. Compost is not typically applied to alfalfa; however, manure application to alfalfa is common in the state’s dairy regions.

The over half a million acres of alfalfa in California could represent an important repository for compost, for which a large land base of spreading may be needed as municipalities convert organic waste management streams to compost to divert from landfills.

Alfalfa has the ability to take up large amounts of nitrogen and phosphorus from the soil, which are harvested and removed in the crop. These nutrients are of concern in organic wastes due to their potential to contribute to water pollution.  Furthermore, alfalfa growers are interested in the potential of compost to improve soil structure in their alfalfa fields, as many growers report suffering from poor soil conditions.  Composts can improve infiltration and the acids generated by composts can improve soil structure and improve nutrient availability.  Often, large cracks form in heavy soils can cause poor soil structure due to the wetting and drying cycles of alfalfa surface irrigation management.  This wetting and drying cycle can also be deleterious to soil microbial health.

Compost application has been anecdotally reported to alleviate soil cracking in another perennial crop, almond orchards, in the Central Valley, but soil structure improvement via management practices like compost application has received little research attention thus far.  Through this project, we will evaluate compost application to alfalfa for improving soil health. — By Rachael Freeman Long, Michelle Leinfelder-Miles & Dan Putnam (UC Cooperative Extension)

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