Linking soil quality, plant health, and animal nutrition on dairy farms through energy and nitrogen balance

Linking soil quality, plant health, and animal nutrition on dairy farms through energy and nitrogen balance

Summary

Farmers experienced in sustainable agriculture manage soil organic matter for nutrient balance through associated biological processes. Many of these farmers have observed that “healthy soil grows healthy plants, which in turn grow healthy animals.” Yet there is little research directly addressing the link between soil, plant, and animal health. We hypothesize that soils managed with biologically based fertility grow plants which have biochemical characteristics causing them to be less susceptible to insect attack while at the same time more efficiently metabolized by cows. Specifically, our theoretical model predicts that health and efficiency of the soil, plant, and ruminant animal increase when carbon (C) and nitrogen (N) are in balance, because metabolism and production are closely linked. This hypothesis will be addressed with three objectives:

1) Identify key linkages between the soil and plants in terms of nutrient and energy balance,
2) Measure the quantity and form of substrate available to microbes in the soil and rumen, in the context of nutrient and energy balance,
3) Collect the whole-farm data on nutrient inputs and outputs, to describe the link between nutrient balance, efficiency, and health on dairy farms.

We plan to characterize soil and plant nutrient dynamics across a range of farming practices. Of the farms selected, some use only organic N inputs while others apply moderate to high levels of inorganic N. By monitoring the carbon and nutrient status of the soil and plants a the beginning and end of the growing season, we will determine nutrient loss versus plant uptake from the soil. Management practices achieving optimal nutrient status will be identified, and regression will be used to identify how patterns in nutrient profiles vary with fertility management.

We will also quantify the amount, ratio, and rate of availability of C and N in the soil, raw forage, and mixed feed as these parameters are important predictors of efficiency and productivity of microbes in the soil and rumen. Soil microbial respiration and N immobilization will quantify soil microbial activity. Milk fat and urea N will provide indicators of rumen microbial functioning.

Through a number of interview sessions, we will determine the costs of feed, fertilizer, herbicides, and pesticides for each farm. Fertility and feed inputs will be compared to crop and animal outputs, including crop and milk quality. Regression will be used to describe correlations between nutrient inputs and variables indicative fo health and efficiency. Results will be discussed with farmers in interviews and at field days, and distributed in extension publication and scientific journals.

The success of the project will be evaluated by farmer feedback on the usefulness of the information generated. Farmers will discuss nutrient trends in their soil, plants, and animal milk with researchers. During interview sessions, farmers and researchers will explore farmers’ goals and how they are manifested in farm outputs, nutrient retention, and crop and animal health. Together, we will interpret the seasonal nutrient levels in differently managed systems, determine impacts on productivity and health, and generate questions for future research.

Collaborators: