Manure Injection – New technology = More Options
The goal: To increase the opportunities for injecting manure into a variety of growing crops with nutrient placement as similar to commercial fertilizer placement as possible.
Traditional manure injection combined manure application with primary or secondary tillage gives the benefit of full disturbance of the soil profile allowing ideal mixing of manure nutrients (even at higher volumes), while minimizing losses from volatilization or preferential flow, and odour issues are usually non-existent. With injection into standing crops, the equipement design needs to be modified. Several toolbar designs were demonstrated at a demonstration day in August 2012 to give producers ideas and compare current options.
Distribution units (equalizer manifolds), tire width, tire sizes, specific tanker specifications are also important considerations but were not considered in this article.
Injection Tools that have been modified for in-crop application
Dennis Nuhn stated at the demonstration that “there is no one best injection unit because needs are different and soil conditions, soil textures vary from farm to farm”. The type popular with haulers (i.e., double disk style injection units) because it gets the job done faster, may not be the the best option for nutrient efficiency, odour control and may not perform as well in no-till or standing crop situations.
Nuhn tanker with Dietrich injection units at ~30 inch spacings – straight coulter followed with knife injection sweep tooth to incorporate manure into an ~ 8 inch band interrupts macropores to eliminate risk of preferential flow. Depending on volume of manure applied the rate in the band is higher than uniform surface application. Application band often has some manure visible therefore some risk of volatilization. In heavier soil types the manure nutrients may not move to the corn roots.
Jamesway unit has injection coulters on a 28 ft. toolbar; each with 4 inch angle from top to surface, injecting manure to about a 4 inch depth at 13 inch spacings along a 28 ft toolbar. The ”smear and sheer action” disturbes macropores channels and relys on rapid infiltration to minimize volatilzation, since the trench remains uncovered. Often used in wheat or forages this design increases uniformity of application compared to 30 inch spacings and reduces risk of losses. The disadvantage of this design is that the manure is applied with smear and sheer effect. Risk of compacted soils with less nutrient movement through the soil profile increases if manure is applied to poorly drained or wet soils.
Pit King tanker – injection design This unit is a heavy duty design that has been modified for Biosolids application. It is designed for applying higher application rates and fully incorporated the manure therefore eliminating odours. The toolbar has a straight tooth design (~6 to 8 inch depth) on a 15 ft toolbar in ~3 ft width spacings with closing discs (Dietrich brand) to incorporate/cover manure in trench and reduce odours. No regulator makes low rate application difficult. This unit creates more disturbance which would make it less ideal for no till or for applications into standing crops. At high volumes, tile drains would need to be monitored for preferential flow.
Veenhuis Injection unit Coulters in 7.5 inch spacings create 1-2 inch deep trench and place manure into the trench. Close spacings result in lower volume per row therefore infiltration is rapid. Disturbance is minimal which makes this unit ideal for forages, pastures or wheat in spring or summer. The advantages: manure distrubution is most similar to commercial fertilizer and nutrients are applied into growing crops when nutrient needs are highest and nitrogen losses are lowest. The drawback: on sloping soils manure can move down slope until infiltration occurs. This toolbar does not work well in tilled soils because there isn’t enough clearance for loose residue (residue creates a shovel-effect resulting in clogging) and stones can become lodged between the coulters.
Shallow Application toolbar This toolbar design has coulters in ~10 inch spacings create 2-4 inch deep trench and places manure into the trench. Narrow spacings result in lower volume per row therefore infiltration is more rapid. Application into growing crops (wheat, planted or standing corn, soybeans, no-till, slurry seeding cover crops after wheat harvest) maximizes nutrients and minimizes leaching and (greenhouse gas) nitrous oxide losses. In standing corn the coulters can be set on the toolbar to apply manure close to the corn row for maximum nutrient contribution and minimum potential losses. Different coulter types can alter the amount or type of tillage action.