Manure is a very valuable source of a full spectrum of nutrients like nitrogen (N), phosphorus (P), potassium (K) and sulphur (S) as well as a range of micronutrients. Manure, especially in solid forms, also contains organic matter which can improve the structure, aeration and water holding capacity of soil. It most certainly has drawbacks for use in conventional cropping systems, however.
Manures from different sources have different nutrient content and ratios. Assessing the rate of application is not easy as the manure’s constituent nutrients can vary within the manure itself, making it hard even to collect a representative sample for testing. Applying manure can be challenging because it’s not a simple thing to control or change the rate of application as a farmer would with synthetic fertilizers.
EXTRACTING TOP VALUE
So how to extract the most value from manure for the highest yield potential?
Livestock producers, particularly in the pork industry, are looking at using new technologies to separate manure into different component streams and make it more valuable to producers whilst limiting its environmental impact, especially in light of stricter P management regulations.
“We want to make it cost effective to efficiently handle the manure without compromising the environment,” says Matt Reimer of Hylife. “By separating it and concentrating our different nutrients into different streams it makes it easier to manage areas that are too high in certain nutrients and now we can address that by making sure we are not applying a nutrient rich product in that area and applying it somewhere where that nutrient is deficient.”
Grain farmers are looking at manure as a cheaper alternative to the increasingly expensive synthetic fertilizers, and one which would give them more “bang” for their buck, particularly in terms of nutrients like P and N.
“Rising costs for synthetic fertilizer are a factor stimulating interest in manure,” says Don Flaten, a soil fertility expert with the department of soil science at the University of Manitoba. “On the other hand, given the other high costs associated with grain and oilseed production, crop producers are also becoming very particular about making sure that the availability of nutrients from the manure matches their crop requirements.”
At a recent soil and manure management field clinic held at the Canada-Manitoba Crop Diversification Centre (CMCDC) at Portage la Prairie around 50 participants including farmers, hog industry representatives and researchers had a chance to discuss topics around manure nutrient management and application.
They examined test plots of wheat that had received applications of different manure types, in both liquid and solid forms. The plots were soil tested to determine what nutrients, and in what concentrations, were present.
Two types of separated manure were applied. One was separated by a screw press from a dairy operation and the other from LWR (liquid water recycler) equipment at a pig operation. The advanced technology of the LWR system separated the pig manure into three different streams — two liquid and one solid. The manures were then applied at recommended book value and compared against a control plot of untreated solid manure.
With the dairy manure solids there was absolutely no N response. There was less available N in these plots than in the control plot. “There is so much carbon with the manure solids that is taking all the N out of the soil to break it down,” says Curtis Cavers, an agronomist with CMCDC. “With the liquid dairy manure we were applying based on N rates and we still had enough P for the crop to grow that year, so we matched the 5:1 N to P ratio that we would be seeking for a typical grain crop.”
The separated liquid byproduct from the pig manure achieved the required goal for N but contained no P. “The LWR separator system did a good job of separating the P from the liquid component, which is what pig farmers are going to be looking for,” says Cavers. “The pig manure solids did the exact opposite of what the dairy solids did. We could achieve the N rates with the solid component from the pig (manure) because there is almost no carbon in that material compared to the dairy.”
Along with N, the separated pig manure solids also provided around a ten year supply of P, so while the separation system did a good job of removing P from the liquid component, the solids, as a result, had a much higher concentration of P, making it much harder to handle and apply with any standard manure application equipment.
Just as technology is helping to better determine and control the content of livestock manure, it is also helping to apply it more accurately and responsively. The field clinic also compared a new, vertical beater solid manure spreader to a traditional, horizontal beater manure spreader.
A big plus to the vertical design is that it throws the manure sideways, increasing the spreading area and lowering the rate of application per acre. Also, the beaters inside are more closely positioned and the manure is forced through a very tight space which chops it into finer particles and allows lower and more uniform application rates to be achieved more easily.
The two applicators were used across the field and applied the manure under different conditions, at different speeds and using different hydraulic settings to allow participants to compare the spread patterns and densities and allow an interactive discussion about some potential challenges and solutions. “The exercise led to a good discussion about proper techniques to calibrate application equipment and then deliver a target rate,” says Cavers.
Participants did an elaborate exercise to try and collect the data needed to estimate the application rate using simple equipment like a measuring wheel and tape measure. They measured the length and width of a spread area to determine the area of application, then measured the height, width and length of the manure spreader to determine its volume. The final piece of the “pie” was to determine the density of the manure, which they did by dumping it into a five gallon pail and weighing it, then dividing the weight of the pail by its volume. They then used this data and a formula contained in tri-provincial guidelines for estimating manure application rates to come up with a rate (find them at www.gov.mb.ca/agriculture/ crops/cropproduction/gaa01d39. html). “The number they came up with from the exercise wasn’t really the point,” says Cavers. “It was about showing them what pieces of information they need to generate that answer and what are the confounding factors that can influence the end goal, which is to apply the manure at the desired rate based on crop nutrient requirements.”
Few farmers are likely to repeat this exercise in every field, so a simpler solution, says Cavers, would be to simply determine the capacity of the spreader and then count loads, and knowing how large a field is in acres, they can simply divide the number of loads by the number of acres to estimate tons of manure per acre.
MANURE IN CONVENTIONAL CROPPING SYSTEMS
Scientists are working on new research projects and facilities to bring the needs of the livestock industry and the needs of crop farmers together and hasten the process of finding answers to the challenges of managing livestock waste in an ecologically sound way that also provides added value for farmers.
A research project just getting underway at the University of Manitoba, in collaboration with the Prairie Agricultural Machinery Institute (PAMI) and Puratone Corporation, is looking at ways to use separated pig manure products to sustainably utilize and conserve the P content to maximize crop performance.
“This group is evaluating not only the separation technology in the system, but various members of the team are also evaluating the chemical composition of the solids and its suitability for application on agricultural land, as well as the benefits of composted solids for improving crop production,” says Flaten. “We also have research teams associated with the National Centre for Livestock and the Environment (NCLE) that are exploring more advanced technologies for manure processing such as enhanced anaerobic digestion and struvite fertilizer recovery from liquid manure”
A new Agricultural By-Products Processing and Demonstration Facility is also soon to be built at the University of Manitoba, which will complement the existing equipment and facilities used by the NCLE and its partners. The facility will enable on-farm processing and utilization of liquid and solid agricultural by-products from livestock production, such as manure and mortalities, as well as from fibre and biofuel processing -adding value to materials that are otherwise viewed as “waste.”