USA - University ag experts warn salt in manure can harm crops
Published:October 4, 2004
Source :KansasCity.com
Applying manure to crops through center pivot systems can be a cost-cutter when it comes to fertilizing crops. But University of Nebraska ag experts say farmers need to know how much is too much.
The reason, experts say, is that salt in manure can damage plants.
NU scientists recently conducted experiments near Concord to find out when and how much swine manure can be safely applied to corn and soybeans.
The effects of salt accumulations in soil are well studied. But NU's research focused on salt's effects on growing crops, soil scientist Charles Shapiro said.
"Farmers want to know when and how much manure they can put on their crops before the salt in manure would be toxic to the plants," Shapiro said.
Researchers applied manure through a custom spray system that simulated pivots but allowed different application schemes on small test plots.
They checked manure's salt content using electrical conductivity meters. Higher readings mean more salt.
Liquid manure from a pit was applied to corn and soybeans in early or late July at three concentrations. Some plots received undiluted manure with an electrical conductivity of 20, some got a 50-50 water-manure mix with a measure of 12, and others received a mix of 75 percent water and 25 percent manure with a measure of six.
While those concentrations were higher than farmers typically apply, scientists wanted to test the limits for growing crops.
The research found that applications of undiluted swine manure killed three-fourths of soybeans and some corn.
Applications of the half water-half manure mixture stunted soybeans, yellowed leaves and reduced leaf area. In corn, effects were less severe.
The lower concentrations of manure to water yielded the best results.
Researchers concluded that manure with electrical conductivity of 6 or less should be safe for corn and soybeans at all growth stages. Values of 12 should be safe for soybeans and corn by late July, they said.
