Effect of Waste Milk Application on Reclaimed CRP Grassland Health and Ecosystem Services

Progress report for GS23-292

Project Type: Graduate Student
Funds awarded in 2023: $14,874.00
Projected End Date: 08/31/2025
Grant Recipient: TTU NRM
Region: Southern
State: Texas
Graduate Student:
Major Professor:
Dr. Caitlyn Cooper-Norris
Texas Tech University
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Project Information


Dairy production in Texas is one of the fastest growing agricultural sectors, with billions of gallons being produced and sold each year. However, with the production of useable milk comes an increase of milk not fit for human consumption, or “waste” milk. Previous studies have shown that a mixture of waste milk and water can act as a fertilizer, causing rapid growth and more available protein in plants. In addition to this, the milk solution can mitigate soil acidity, acting as both a fertilizer and a lime. In the Texas High Plains, many counties are leading dairy producers, but also comprise a large proportion of the state’s acreage enrolled in the Conservation Reserve Program. This study intends to assess the effects of land application of milk on vegetative cover, yield, and species composition of native pastures; soil health; and ecosystem services. Vegetative measurements will include collection of vegetative cover and composition data along transects and clippings to monitor biomass production and forage nutritive value. Soil health will be measured in form of pH, bulk density, carbon sequestration, and microbial activity via CO2 evolution. Four waste milk application rates (0, 10, 20, and 40 lbs of N per acre) will be applied in controlled greenhouse settings and in field settings on CRP properties. 

Project Objectives:

The objectives for this research are to evaluate how various application rates of milk (0, 10, 20, and 40 lbs of N/acre) will influence: 

  • species composition and yield of native pastures
  • forage quality through alterations to protein and digestibility
  • soil health parameters (e.g., pH, microbial activity, respiration, and carbon sequestration)


Materials and methods:

Greenhouse trials:

Greenhouse trials will involve waste milk application to individual blue grama plants grown in 1-gal grow bags. Milk will be applied in appropriate volumes to provide N rates equivalent 0, 10, 20, and 40 lbs of N/ac. 18 pots will be allocated to each of the four treatments. Prior to milk application in May 2024, a subset of 6 pots per treatment will be destructively harvested to assess above and below ground biomass production. Following milk application, additional subsets of pots will be harvested in the same manner in June, August, and October 2024. Measurements will include assessments of above and below ground biomass and reproductive shoot production. Basic soil analyses will assess changes in soil nutrients over time after milk application. Soil C fluxes will be evaluated using an in vitro procedure and will provide information about the effects of milk application on microbial activity. 

Blue grama plants to be used in greenhouse trials are currently being grown in a laboratory at Texas Tech University. In early April 2024, the blue grama plugs will be transplanted into 1-gal grow bags in the greenhouse and the trial will commence. 

Field trials: 

Three properties in Hartley County, Texas with existing CRP land will be used for this portion of the project. Pastures must have a minimum of 50 acres to qualify for this study and have been enrolled in the CRP program for at least three years. Within the pastures, ARC GIS will be used to randomly select four plots of approximately 11,000 ft2 with a minimum of 1000 ft between each plot. Plots will be mapped out using GPS and staked with rebar upon arrival at each pasture.

Waste milk will be collected or donated from a local dairy and will be applied in appropriate volumes to provide 0, 10, 20, and 40 lbs of N/ac. Each N rate will be applied to a random quarter-acre plot of established CRP grassland.

Three trips will be used during June, August, and October to evaluate the effect each solution has on vegetation and soil during the growing season. Prior to the first trip, three randomized points will be selected within each plot to use for transect evaluation. At each point, two 50 meter transect lines will be stretched in two random cardinal directions. Along each transect line, every five meters a 0.25 by 0.50 m sampling frame will be placed on the right side. Cover percentage of species and vegetation classification will be evaluated and recorded for each frame, and vegetation will be clipped and placed into bags for drying and weighing later. Nutritive value will be determined on biomass samples by sending to an external laboratory for a basic nutritional profile, including crude protein, neutral detergent fiber, acid detergent fiber, ether extract, and total digestible nutrients.

Soil sampling will occur in a grid pattern evenly spaced within each plot, with 25 six inch cores being collected in total for each plot. Soil cores will be composited in a five gallon bucket, then placed into bags for drying. Composited samples will be ground using mortar and pestle, then a sieve will be used to sift out any organic material greater than 2 mm in size. A small amount of each sample will be combined with DI water and tested for pH for each plot. Microbial activity will be tested by fumigating 12 grams of each sample for 24 hours, then testing using potassium chloride method with a spectrophotometer. Remaining soil samples will be sent to an external laboratory for a general soil test. All procedures and sampling will be completed for each of the four plots on each property.

Research results and discussion:

We have no results yet from our greenhouse and field trials. 

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

We have not yet conducted any education or outreach activities. 

Project Outcomes

Project outcomes:

We have no outcomes to report at this time. 


We have no recommendations to report at this time. 

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.