Field Scale Management of Separated Dairy Manure Fractions

Why Look at Separated Manure for Crops?

Research at Pacific Agriculture Research Centre (PARC) by Agriculture and Agri-Food Canada (AAFC) in Agassiz, B.C. has shown that targeted application of separated liquid and thicker sludge fractions from dairy manure slurry on grass and corn, respectively, can improve crop nutrient efficiencies, reduce the requirement for commercial fertilizer, and reduce nutrient losses to the environment. These benefits are in comparison to the traditional practice of surface broadcast application of agitated raw slurry manure. More specifically, the liquid fraction, applied via surface banding to grass fields, helps to improve infiltration, reduces ammonia emissions, and improves grass yield and nitrogen recovery. The thicker sludge fraction, which contains more phosphorus, is precision deep injected, then planted with corn near or over the injection furrows. This replaces the need for commercial phosphorus fertilizer normally applied as a starter during corn planting. The sludge fraction is obtained from sedimented slurry.

precision manure injector and tractorThe overall objective of our two year project is to assess these improved manure application practices at the farm scale through various sub-objectives. First, sedimentation efficiency is being evaluated on farms with contrasting manure management by sampling liquid storages at various depths prior to agitation. The goal is to assess natural stratification of nutrients under different bedding and water management, and to assess the practicality of sequentially pumping the thin supernatant (late Mar- early Apr) and thicker sludge (late Apr- early May). Second, improved equipment is being developed to precision deep inject slurry sludge (6 – 11% dry matter) prior to corn planting. Third, on-farm field scale trials using improved manure application equipment are assessing the agronomic and economic benefits of managing separated dairy manure fractions, compared to the traditional practice of surface broadcasted agitated raw manure.

precision maure injector in useWhat did we do?

We have completed one year of this two year project. Progress has been made on all three sub-objectives, but most notably on the first. Under the first sub-objective we have sampled manure at various depths for 18 liquid manure storages, and collected management information on bedding management and water inputs into these storages.

We also utilized a custom manure operator to mount a farm scale 4 row deep manure injector onto a dragline system. This was used to precision deep inject thicker dairy sludge and compare with traditional surface broadcast application and incorporation, prior to corn planting on a farm field near Agassiz, B.C. On this same farm a different custom manure operator applied thinner dairy slurry on a grass field using first a shallow disc injector and then a trailing hose. These two treatments were compared with the farmer’s surface broadcast application.

These manure applications on grass occurred two times, once in March and once in May. While it would have been preferable to use agitated raw manure for the farmer’s surface broadcast application on both grass and corn, this is not feasible when managing a farm’s manure supply from a single storage system. Rather the same manure sources, ie. thin slurry on grass and thicker sludge on corn, were used for all application treatments, including the farmer’s broadcast application.

the plots where the precision manure injector study was performedWhat have we learned?

Average nutrient content of liquid manure in storages varied greatly between farms, ranging from 0.58 to 2.80 kg/m3 for total nitrogen and 0.17 to 1.51 kg/m3 for total phosphorus (expressed as P2O5). These nutrient values were closely correlated with dry matter content, which ranged from 0.58 to 10.02%. Variation in dry matter content is determined primarily by the amount of water inputs into the manure storage, the amount of organic bedding imported onto the farm, and whether the raw manure undergoes a mechanical solid/liquid separation process prior to the liquid manure entering the storage.

Seven out of 18 storages had little or no sedimentation of solids or nutrients. Four storages showed slight stratification and the remaining seven storages had considerable settling of solids and nutrient concentration increasing with depth. For storages with considerable stratification average dry matter content ranged from 1.5% for the shallowest depths to 7.7% for the deepest depths. For these same depth positions average total nitrogen increased from 0.090% to 0.193%, and average total phosphorus from 0.015% to 0.041%. Preliminary assessment of manure sample analysis compared to manure management practices suggests that sedimentation of solids and nutrient stratification is minimal or reduced when coarse solids are mechanically separated from liquid manure prior to entering storage, and/or there is considerable disturbance of manure when transferring it from the barn into the manure storage. For example, manure pumping involves more disturbance than scraping.

Preliminary results from land applied manure suggest small but likely insignificant increases in dry matter yield for trailing hose and shallow injection on grass compared to surface broadcast manure. On corn land there was no difference in yield between deep injected and surface broadcast/incorporated dairy sludge. Part of the reason for little or no difference is due to using the same manure source and application rate for all treatments. Also, the corn land result may be due to the majority of nutrients for both treatments being supplied by another source, surface broadcast poultry manure.

Future Plans

In the winter of 2015 most liquid manure storages will be resampled. An additional 5 liquid manure storages have been chosen for sampling in 2015, to include some manure management systems not accounted for in 2014. Our 4 row deep manure injector is being modified to a 6 row unit. This will enable easier alignment of the manure furrow with subsequent 6 row corn planter. We plan to add two more farm sites to land apply separated manure fractions on grass and corn, for the 2015 growing season.


Dennis Haak, Senior Soil Resource Specialist, Agriculture and Agri-Food Canada

Shabtai Bittman, Research Scientist, Agriculture and Agri-Food Canada; Derek Hunt, Biologist, Agriculture and Agri-Food Canada

Additional information             

1. Precision Placement of Separated Dairy Sludge Improves Early Phosphorus Nutrition and Growth in Corn (Zea mays L.),

2. Removing Solids Improves Response of Grass to Surface-Banded Dairy Manure Slurry: A Multiyear Study,

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