Management of an On-Farm Composting System

Management of an On-Farm Composting System

Summary

Objectives

1. Determine the fate of nutrients in an on-farm composting management system.

2. Develop a management plan to optimize the value of the composted end-product.

3. Demonstrate the management system to local producers.

4. Distribute information through the Cooperative Extension Service.

5. Analyze the economic and labor requirements of the management system.

Abstract

Experiments were conducted at Utah State University in Logan, Utah, from the fall of 1993 to the winter of 1994 to evaluate the feasibility of composting in a cold, arid climate. The windrow method of composting was used on an outside composting pad. Composting appears feasible in a cold, arid climate. However, turning may not be feasible if water cannot be applied to the compost windrows to maintain proper windrow moisture content (between 40 and 60%). There was a significant difference in most of the elements tested between the raw materials and the ending compost. Soluble salts, phosphorous (P), and potassium (K) levels were high in soils under the intense management regimes. A concrete or asphalt pad to prevent leaching and improve access to the composting site may be beneficial for producers to consider. Results will be useful in facilitating on-farm composting as a dairy waste management practice in northern Utah and more generally, the Intermountain West.

Characteristics of compost at the beginning and ending of the treatments [(1) no turning/no water, (2) no turning/water, (3) turning/no water, and (4) turning/water] were analyzed for NO3-N, P, K, and soluble salts using an ANOVA for a randomized complete block design.

Concentrations of soluble salt increased during composting in all treatments during the spring and summer of 1994 (p = 0.05). Phosphorous concentrations decreased significantly in all treatments (p = 0.05) during the spring and summer of 1994. In the fall of 1993, potassium levels generally decreased, especially in the no turning windrows. There were significant (p = 0.05) decreases in all treatments during the fall of 1993 and for treatments 3 and 4 for spring of 1994 (p = 0.05), and treatment 1 for summer of 1994 (p = 0.05). No significant statistical differences were observed in any of the treatments for nitrate for fall of 1993 and spring of 1994. Nitrate levels increased in treatments 1 and 2 during the summer of 1994 (p = 0.05).

Composting in a cold, arid climate such as northern Utah appears feasible with moisture as a limiting factor. The cold, arid climate of the Intermountain West provides a wide range of environmental conditions, which producers must consider when managing compost. In the spring, animal wastes are high in moisture content (>80%), and considerable amounts of drier materials must be added to lower the moisture level for proper composting. Also, wetter materials must be turned more frequently than normal to facilitate drying. During the summer months when water is limited, windrows should be turned when evaporative losses are low (at night, or after a rain event). However, water must be added during the summer and windrows must be turned frequently to reach the high temperatures required to destroy weed seeds. Methods to minimize moisture loss may need to be developed during the summer months. Covering windrows with a compost windrow fabric may be one such method to help conserve moisture during the summer months. In the fall of the year when there is usually more precipitation, evaporative losses are less of a concern. Evaporative losses are also less of a concern during the winter. We did not determine the extra time needed to compost materials if additional water was not added. The relationship between composting and moisture management warrants additional study.

Two key elements that do not receive much attention when managing soils are phosphorous and potassium. Potassium requirements of plants are high during early stages of growth, and it is important to provide adequate (but not excessive) amounts. Compost contains relatively large amounts of potassium and should be applied on the basis of soil tests. Heavy applications of compost may exceed plant requirements of phosphorous and potassium may lead to other problems in the soil or future crops. Perhaps smaller split applications may be warranted to avoid excesses of phosphorous and potassium, which may dictate management more than nitrogen.

Soluble salt concentrations in the compost were as high as 34 mmhos/cm for some of the individual treatments in the study and the salt content of compost should also be considered when applying compost to the soil. It is not always possible or practical to eliminate all salts from the soil, but managing the soil and the amount of compost applied to the soil may help to minimize salt damage in soils and to plants. Maintaining a high water content in the soil, near field capacity, dilutes salts and lessens their toxic and osmotic effects (Donahue, Miller, & Shickluna, 1983). Thus, irrigating soil lightly but frequently to elevate moisture content during the salt-sensitive germination and seedling stage should help, plants tolerate salinity associated with compost. If large amounts of compost are applied, some salt will accumulate in the soil surface or furrow ridge tops as water moves upward and evaporates.

The management system and associated technologies was demonstrated to local producers, agency personnel and Extension Field Staff through the use of Utah Agricultural Experiment Station field days in July of 1995 and 1996. An article was written for a Utah State University Extension Service insert for the Utah Farm Bureau News. Technology was also transferred through personal contacts as a result of articles in the Utah Farmer-Stockman (July-August 1996) and the Colorado Rancher & Farmer (September 1996). Collaborative regional training sessions are being planned and funded through PDP. A four part Extension Fact Sheet series was developed using information derived from this project.

Potential Benefits

This project provides scientific information and demonstration of an alternative animal waste treatment method. The practice provides farmers with a management tool to improve water quality and enable the producers to treat wastes and possible develop a positive cash flow from their waste management system. The practice seems particularly suited to confined animal operations which have limited access to land for direct disposal of waste products. Composting presents another viable tool for livestock producers in the Intermountain West. It requires additional management by the producer, yet provides a product which may be sold.

This summary was prepared by the project coordinator for the 1998 reporting cycle.

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