While the incorporation of manure has been noted as a fundamental component of sustainable agricultural systems, nutrient management practices for these materials have languished. Traditional laboratory analyses of organic amendments are slow, time consuming and expensive, leading to relatively limited adoption. These methods also mainly quantify macronutrient contents, representing an antiquated notion of nutrient management based simply on achieving cumulative nutrient removal. Analyzing both the elemental content and chemical structure of a specific manure is vital to synchronizing the mineralization of nutrients (supply) with the needs of crop uptake (demand) in sustainable agricultural systems.
Small farms often manage solid manure, which tends to be quite variable in both nutrient quantity and timing availability. A simple, rapid and low-cost method for onsite manure composition analysis would vastly improve nutrient management on these operations. Visible and near-infrared reflectance (VIS- NIR) measurements of manure have been successfully calibrated to both traditional laboratory extractions (moisture, total carbon and nitrogen) and measurements of organic chemical composition (cellulose and lignin)1. While VIS-NIR has been validated extensively on a vast array of organic materials in research settings with great success, technological advances are only now making cost effective portable devices a reality.
This project will examine different methods for onsite testing of manure composition using a full spectroradiometer and low-cost reflectometer. The developed calibrations will be validated, then used in simulations within the Systems Approach to Land Use Sustainability (SALUS) Model to evaluate the long-term dynamics of manure decomposition and its effects on crop yield and soil health. SALUS is a crop and soil biogeochemical model designed to simulate continuous crop, soil, water and nutrient conditions under different management strategies for multiple years. Long term simulations will be used to calculate expected economic and environmental impacts, and to assess the potential of onsite VIS-NIR for precision manure management.
- Althaus, B., Papke, G., and A. Sundrum. Use of near infrared reflectance spectroscopy to assess nitrogen and carbon fractions in dairy cow feces. Anim. Feed & Tech. 185, 53-59.
Project objectives from proposal:
Project participants will gain knowledge on the critical role of nutrient content and biological nature of manures. Refining the rate and timing of manure application based on this understanding will be a key takeaway. Participants will also gain a basic overview of spectral science, and why absorbance of energy by materials might aid in prediction of their makeup. The possibility of realizing improved manure management through rapid, low cost and onsite VIS-NIR analysis yielding both nutrient content and biological composition of manures will be demonstrated. Modeling and visualization will further assist in conveying these concepts in real world scenarios. The current viability and economics of adopting portable spectroscopic technology will be summarized concisely for consideration by those making business decisions.
Actions based on these learning outcomes will principally include modification of manure management plans (MMPs). Limited resource farmers and those consulting them will modify practices based on potential economic and environmental improvements achieved by accounting for both the nutrient content and chemical composition of manures. A smaller subset of progressive producers and consultants will also adopt the use of spectral devices and improve management of manure variability and temporal nutrient cycling through expanded spectral analysis of manures and soils.