Managing Dairy Manure in the Central Valley of California

Report authors: University of California Division of Agriculture and Natural Resources Committee of Experts on Dairy Manure Management

There are approximately 1.7 million lactating dairy cows in California. Sale of milk from these cows is estimated at $4.6 billion of the state’s $30 billion agricultural market. Nearly 73% of the cows are located in the San Joaquin Valley, which consists of San Joaquin, Stanislaus, Merced, Madera, Fresno, Kings, Tulare and Kern counties. The Central Valley Regional Water Quality Control Board submitted a list of questions to Vice President Gomes requesting specific information related to dairy manure. The answers to these questions are the basis for this lengthy report.

The report covers the following topics in depth, relative to manure management:

• nitrogen (N) excretion
• distribution of manure around dairies
• atmospheric N from liquid manure
• developing N application rate guidelines
• phosphorus (P) and potassium (K) in manure
• salts in manure and salinity issues in land application

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