Factors Affecting the Testing of Manure Transported Off the Farm.

The use of manure as a substitute for, or complement to, commercial fertilizer could potentially reduce costs due to increases in energy prices.  However, manure is a heterogeneous product which requires frequent testing.  Adoption of manure testing would decrease the level of uncertainty associated with using manure as an input and allow for more precision in terms of the level of nutrients needed by crops. More efficient use of manure could also reduce non-point source pollution caused by excess nutrient applications. 

A survey of 3000 Iowa and Missouri farmers with animal feeding operations was conducted in the spring of 2006. The effective response rate was 37.4 percent.  Respondents who answered yes to the question of whether they provided manure to other farm operations or individuals in the past two years comprised the subset for this study. The respondents were asked whether either they or the farmer receiving the manure tested it for nutrient content before applying it and this was used as the dependent variable.  Only 53 percent indicated the manure had been tested for nutrient value.

The empirical model for whether agricultural producers tested the manure for nutrient content will be in the theoretical context of utility maximization. The expected utility from testing manure will be denoted by E [U_MT], while the expected utility from not testing manure will be denoted by E[U_N].

y =    1 if E[U_MT] >   E[U_N]

         0 if E[U_MT] <   E[U_N]

The dependent variable TEST took on binary values, whether the manure was tested or not. The following variables, based on the literature, were hypothesized to affect manure testing: age, education, off-farm income, having a comprehensive nutrient management plan, having a contract for the manure transfer, state, aggregate animal units, acres, type of manure, manure storage capacity, fertilizer use, smell bothers me, distance manure transferred, payment for manure, profitability of manure testing, improves water quality, time consuming, complicated practice, and soil testing.

The results of the logistic regression predicted 88.9 % of the cases correctly, and the pseudo r-square measures of model fit were 0.537 for Cox & Snell and 0.717 for Nagelkerke. Furthermore, the Hosmer and Lemeshow Test shows that there is no difference between the observed and predicted values of y, indicating that this model is appropriate for this data set. Finally, diagnostic tests such as the tolerance values and VIF found that the model did not display multicolliniarity.

A number of factors were found to be significant in the adoption of manure testing.  Those with off-farm income levels of $0-$9,999 and $25,000-$49,000 were less likely to test manure than the base category of no off-farm income.  Those with education of less than high school level were more likely to test manure than the base category of high school degree which is contrary to expectations.  Having a contract turned out to have a positive influence on whether the manure was tested for nutrient value. To mitigate any uncertainty, the buyer and seller have an incentive to test the manure if there is a contract negotiated before the actual transfer of manure.  Furthermore, the variable ‘payment for manure’ was found to have a positive and significant influence on manure testing. In this analysis the variable “distance” was expected to have a positive influence on manure testing, since the buyer/recipient who transports the manure a greater distance would want to be assured of the quality of the product.  Distance was significant and positive.  Manure from farmers who only had liquid manure was more likely to be tested than from those who had solid manure and this may be due to the increased variability in dry matter of liquid manure.

Manure and soil testing are complementary practices that, when combined, result in more efficient nutrient applications and can also decrease pollution.  As expected, soil testing was positively associated with the adoption of manure testing.  Individuals who test soil are more likely to test manure since they already realize the benefits of more precise nutrient management.  The perceived effect of manure testing on water quality was not significant, indicating that manure testing is primarily related to the value of the nutrients for crop production, rather than to reducing non-point source pollution.  Educational programs focused on the positive effects of manure testing regarding reduced uncertainty and increased profitability are likely to be more effective than those focused on the water quality impacts.