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Washington State University - Puyallup Organic Farming Systems and Nutrient Management

Soil Quality


Soil Quality

Soil Quality Project, Carnation, WA.

In 2006 we initiated a project at Full Circle Farm in Carnation, WA to describe how soil texture affects the soil food web. To create a detailed soil texture map and see how this inherent soil parameter affected other parameters we took 81 samples across a 62-acre area of FCF. From each site we analyzed soil texture, bulk density, nitrogen, organic matter, and the soil food web.

Soils within the area of the farm sampled varied greatly in texture. There was a strong gradient of increasing sand and decreasing clay from west to east. Sand ranged from 5-54 % while clay ranged from 9-27%. Four texture classes were identified: sandy loam, loam, silt loam, and silty clay loam.

At the field scale we found that much of the variation in nematode population density could be explained by recent tillage, not soil texture. However, sampling in 2007 was designed to control for management effects so we sampled from one field in a sandier area of the farm and one in a more clay-rich area. The sandier field had more than 8 times the number of nematodes as the clay-rich field. Also, within the sandy field, where clay ranged from 10-17%, clay was strongly negatively correlated with the number of nematodes. On the other hand, in the clay-rich field (16-31% clay) there was no correlation between clay and the number of nematodes.

We conclude that within certain ranges the variation in soil physical and chemical properties can affect biological populations. Thus, careful mapping of inherent soil quality parameters should be the first step in monitoring soil biological populations.

♣ Soil Community Structure, Function, and Spatial Variation in an Organic Agroecosystem (PDF-Online, Full Report). D. Collins.

This project was funded by a graduate student research grant from the ♣ Western Sustainable Agriculture Research and Education Program.

Satellite map of Full Circle Farm.

Full Circle Farm soil texture map, percent sand.

Full Circle Farm soil texture map, percent clay.

Full Circle Farm soil texture map, texture class.

Organic Farming Research Photo Gallery

Organic Farming Systems Research Photo Gallery

Photo of manure spreader spreading compost.
Above-manure spreader spreading compost.
Photo of winter cereal rye vetch mix as a cover crop.
Above-Winter cereal rye vetch mix as a cover crop.
Photo of Undercutter that skims just under the surface to cut weed roots while minimally disturbing the soil.
Above-Undercutter skims just under the surface to cut weed roots while minimally disturbing the soil.

 

Photo of spader which is gentler on the soil than rototillers.
Above-spader which is gentler on the soil than rototillers and usually both tills and prepares the seed bed for planting in one pass.
Photo of vetch as a winter cover crop in a former corn planting.
Above-vetch interplanted in a former corn planting as a winter cover crop to protect the soil from erosion and provide nitrogen for a spring or summer crop.
Photo of Allis G tractor and weed basket, weeding row vegetable crop.
Above-Allis G tractor with weed basket, weeding row vegetable crop.
Photo of two Roller/Crimpers, front mounted on tractor to crimp cover crops stems to terminate them while leaving them in place to provide a mulch.
Above-Roller/Crimpers-Front mounted on tractor to crimp cover crops stems to terminate them while leaving them in place to provide a mulch. Two different widths shown.

 

Photo of buckwheat as a short term summer cover crop.
Above-buckwheat as a short term summer cover crop.
Photo of mowing down sudangrass, a summer cover crop.
Above-Sudangrass summer covercrop being flailed.

 

Photo of custom strip tiller unit. Front discs cut cover crop, back unit (see insert photo) is a one blade wide Maschio rototiller that cuts a narrow path for planting crops in while leaving the rest of the soil undisturbed.
Above-Custom strip tiller unit. Front discs cut cover crop, back unit (see insert photo) is a one blade wide Maschio rototiller that cuts a narrow path for planting crops in while leaving the rest of the soil undisturbed.

Supercow: Liquid Manure Applicator


Supercow: A Liquid Manure Applicator for Small Plot Research

A.I. Bary, D.M. Sullivan, S.C. Fransen, and C.G. Cogger
2001. Agronomy J. 93:1344-1345.
(♣ PDF of full article-Online)

Small-plot research in manure nutrient management requires accurate manure applicators that are easy to operate and maneuver. Our objective was to design a small-plot liquid manure applicator that could apply variable rates of dairy manure containing up to 60 g kg-1 solids to perennial grass plots while avoiding traffic and compaction on the plots. The applicator consists of a 1000-L fiberglass agitation tank mounted on four load cells, a delivery pump and motor, and a side-mounted boom with four nozzles for manure application, all built onto a wagon and towed by a tractor. The side-mounted boom allows manure application without traffic on the plots. Manure application typically was within 7% of the target rate and had a coefficient of variation ranging from 2 to 17%, measured over a series of rates from 53 to 211 MG ha-1 (wet weight). The precision, accuracy, and ease of operation of the liquid manure applicator met our research requirements. Efficiency of operation could be improved using a larger agitation tank.

Supercow Liquid Manure Applicator spraying forage research plots with manure.
Above, Supercow Liquid Manure Applicator spraying forage research plots with manure.
Supercow Liquid Manure Applicator spraying research forage plots.
Above, closeup of Supercow Liquid Manure Applicator spraying research forage plots.
Freshly applied manure by Supercow Liquid Manure Applicator.
Above, freshly applied manure by Supercow Liquid Manure Applicator.

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Overview of our Program

Soils & Organic Farming Systems

Beginning in 2002, we expanded our focus to organic farming systems, including organic amendments, cover crops, and quality of soils. We are working with an interdisciplinary team studying a range of issues important to small scale, direct-market, and organic agriculture, including nutrient management, food safety, soil quality, weed management, economics, marketing, and on-farm research.

Land Application of Organic Wastes

Many organic wastes contain nutrients and organic matter that can benefit plant growth and soil productivity. Recycling these materials onto land captures nutrients that would otherwise be lost, and helps sustain our resource base. They are also a source of organic matter for soils, building and maintaining soil quality. Organic wastes may contain pathogens and small amounts of toxic materials, which can become pollutants if the materials are not managed properly. Over-application of some organic wastes can result in excessive levels of nutrients in the soil, which can harm crop production or water quality. We study nutrient availability from organic materials, to enable us to determine appropriate rates and timing of applications for crop production. We also evaluate short and long term effects of organic amendments on soil quality in agricultural and urban soils.

Our Goal

The goal of our program is to build soil productivity, support local agriculture, protect water quality, and facilitate recycling of organic wastes, by applying soil science principles to agricultural, development, and waste management issues.