Dairy cows

The Idaho legislature is considering a bill that would extend to use of two types of phosphorus tests on fields where manure is applied.

The Idaho Senate Agricultural Affairs Committee voted March 2 to send a dairy nutrient-testing bill to the full Senate with a do-pass recommendation.

The House Feb. 22 passed House Bill 51 by a  61-9 margin.

HB 51 would allow dairy producers to continue monitoring the land application of manure by either the phosphorous-threshold standard or the phosphorous-indexing standard. The Idaho state Department of Agriculture since 2017 has allowed both.

Without the legislation, the phosphorous-threshold standard would “sunset” July 1, 2023, and no longer be available.

The state ranks third in the U.S. in milk production.

Idaho Dairymen’s Association CEO Rick Naerebout said HB 51 would allow producers to continue to choose which monitoring system works best for their situation.

The threshold standard only looks at soil tests. It requires that the dairy maintain a soil test value of 40 parts per million or less for phosphorus.

Naerebout said the indexing standard allows a soil test of higher than 40 ppm in the nutrient-management planning system but considers other field characteristics such as slope, surface-water connection and leaching and runoff potential to determine the likelihood of phosphorous loss. Lower risk of phosphorous loss allows higher levels of manure application on fields.

He said producers with higher-testing fields are likelier to use the indexing system — developed by the Idaho dairy industry and USDA Agricultural Research Service in Kimberly, and introduced in 2017.

Producers whose fields test lower are more likely to use the threshold system, which has been used for 20 years.

Phosphorous monitoring is part of state-required dairy nutrient-management plans.

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