By Deanne Meyer, Ph.D., Livestock Waste Management Specialist, UC Davis, Department of Animal Science, UC ANR
Choppers are going full throttle. That means it’s time to record harvested forage weights and sample forages from each field where manure was applied. These records and sample results determine how many pounds of nutrients, specifically nitrogen, were removed from each field. Obtaining a representative sample is essential to determine your field nutrient balances.
Use a consultant? Have a conversation with the individual doing the sampling. Understand how your samples are taken. Then, determine if you want the process to change, since good sampling is essential to nutrient management and critical to achieving accurate nutrient balances. Multiple grab samples taken throughout the day will contribute to a more representative composite sample. Each grab sample should be stored in a cool place, out of sunlight. A composite sample is made by mixing all the grab samples and quartering the mass until the desired sample size is achieved.
Weigh all trucks. That’s the first big step for your precise data. Next, collect a representative sample from each field. That means grabbing multiple handfuls of chopped forage from many trucks.Once corn, sorghum, or sudan is removed, then it’s time for solid manure to be applied to fields. As with forages, the quantity (weight) of manure applied to each field is required. Sampling is also required.
Multiple sources of solid manure may exist on your facility. Check your Sampling and Analysis Plan to refresh your memory on the sources of manure to sample (lactating cow corral solids, heifer corral solids, separator solids, etc.). As with forages, multiple grab samples are needed (10 or 20) to collect material for the composite sample.
As you know, dried manures vary tremendously from the outside 18 inches to deeper than 18 inches. That’s why so many grab samples are needed to represent what is applied. Pay particular attention to obtaining most of the samples (70 to 80%) from the inside of piles.
Keeping good records of harvested forage and manure application weights makes it easier and more precise to track your nutrient management information. All sample data are used along with weight data to determine total nitrogen applied to and removed from each field.
May the cooler days ahead come with rain!