Can I Irrigate Animal Manures on Growing Crops?

Can I Irrigate Animal Manures on Growing Crops?

The high rainfalls experienced in recent weeks have left many feedlot holding ponds full and operators looking for irrigation options for applying animal manure during the growing season. This article focuses on important considerations for application of open lot holding pond effluent and diluted manures during the growing season without damaging the crop. Three take home messages from this article include:

Under the wrong circumstances, animal manure/effluent applied to growing crops can damage plant tissue and impact yields. However, good alternatives do exist during the growing season.
Under some unique circumstances, the salts in manure/effluent can impact soil salinity. But these circumstances are not common and can be avoided.
A few important questions should be asked before applying animal manure/effluent to a growing crop.
Irrigated animal/manures/effluent can be an excellent replacement for commercial fertilizer with crop yield maintained or increased. For example, a research team from Colorado State and Iowa State Universities demonstrated that “sprinkler-applied swine effluent at the recommended agronomic rate resulted in maximum yields and minimal N accumulation below the crop root zone.” The study further shared that “applications of swine effluent at different times during the growing season appears to be effective … as no plant leaf burn was observed, even at high application rates.” Salt Damage to Crop Tissue 
Soil, manure and water salinity are measured by electrical conductivity (EC). The most commonly used EC units are deciSiemens per meter (dS/m). Crop damage from sprinkler irrigation of manures with higher EC has been observed because of the direct contact of salts with plant tissue. Some factors to consider include:

Knowledge of manure’s salt concentration (or electrical conductivity) is essential. Measuring manure/effluent EC with a low cost electrical conductivity meter (or laboratory test) is essential prior to application. Retired UNL faculty member, Charles Shapiro, observed that liquid manures with an EC greater than 6 dS/m should not be applied during early vegetative growth for soybeans (Shapiro, 2005). EC below 12 dS/m were tolerated when applied at flowering. The Colorado State research sited above use swine lagoon effluent ranging from 4 to 5 dS/m on corn without concerns.
Shapiro observed that corn was more tolerant than soybean with damage in corn only observed for an EC of 20 dS/m. Another researcher suggested that plant tissue susceptibility to injury varied (least to greatest) with sugar beets

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      A few important questions should be asked before applying animal manure/effluent to a growing crop.

      Image Credit
      Photo courtesy of Larry Howard

    Source: Dairy Herd