Can low-cost NIR reflectometers predict Potential Mineralizable Nitrogen in organic farms?

Commodities

Practices

Can hand-held reflectometers predict Potential Mineralizable Nitrogen in organic farms?

Majority of growers report seeking further support in managing nutrients in their farms. Nutrient supply is challenging in organic systems because synthetic fertilizers are prohibited. Knowledge of the biotic and abiotic processes in an organic farm is key in understanding the nutrient demand in organic systems. As such, farmers usually send soil samples to soil testing centers to understand soil properties that help make informed decisions about managing Nitrogen in their farms. These traditional lab analyses are time consuming, expensive, and require the use of harsh chemicals. NIR reflectometers are cheap, rapid, relatively easy to use, and allow non-destructive and repeated soil sampling of near-infrared reflectance which is tested to predict several soil properties of interest to farmers. 

Organic farms sometimes must rely on organic sources of N such as from cover crop residues, as manure demand is very high. Potential mineralizable N is an excellent metric that allows farmers to estimate the amount of N supplied by inputs (manure, residue, etc).While NIR reflectometers are widely used to estimate total soil C and N, their use to estimate PMN is limited.

Here, we will examine the use of two reflectometers to estimate soil PMN from 14 organic farms planted with three cover crop treatments (cereal rye, crimson clover, and a 4 way-mix of cereal rye, crimson clover, rapeseed, and oats) for two years. The objectives are to:

1. Evaluate the efficacy of hand-held spectrometers to estimate PMN.
2. Develop predictive models using hand-held spectrometers that provide measures of PMN.
3. Compare PMN estimates from NIR hand-held spectrometers with bench top MIR spectroscopy to develop guides tailored to farmers.

We hypothesize that the variation in PMN across farms and cover crop treamtens can be explained by the spectral infomration from the reflectometers, additional soil properties can improve PMN predictions, and MIR spectroscopy estimates are better associated with PMN lab measurements than NIR spectroscopy. 

We will plan to demonstrate the use of hand-held reflectometers in a farmers' field day, publish a grower oriented article and a scientific article, along with an instructional video as project deliverables. We will evaluate the outreach impact of our study based on famers responses of their perception pre and post study, and with metrics such as citations, farmer adoption post project completion. Our project will introduce farmers to spectral data and its use in predicting soil properties of interest. 

As a learning outcome, growers will get a one-on-one demonstration on using hand-held reflectometers. Growers will gain practical knowledge of spectral data and its use in predicting soil properties based on a grower-oriented article in the Organic Broadcaster Magazine, and an instruction YouTube video. Growers will advance their knowledge on alternative options to lab soil testing to better manage nutrients in their farms. Researchers and extension educators will learn about the predictive capacity of NIR reflectometers. As an action outcome, growers can use reflectometers to make informed decisions about nutrient management. Researchers will leverage new studies based on our findings from this project.