What new organic fertilizer is ready to compete with manure

Pellets made from low-quality sheep's wool can be a new organic fertilizer suitable for a carbon farm. American scientists compared the effect of granulated sheep wool with a standard commercial fertilizer for the organic sector on the productivity and growth of tomato and spinach plants.

This is reported by the research team of the Department of Plant and Soil Science and the Center for Sustainable Agriculture of the University of Vermont in an article published in the journal Agronomy 2022 on the MDPI portal.

“Nitrogen fertilizers are essential in both conventional and organic crop production. However, in organic systems, the limited availability of approved supplements contributes to high production costs and can result in reduced crop yields and farm profitability. – Written by Terence Bradshaw and Kimberley Hagen. - Therefore, organic growers include leguminous cover crops in crop rotations either during the growing season (inter-row or row rotation) or during non-productive seasons (fallow cover crops).

Legumes supply nitrogen to subsequent crops through symbiotic bacteria that fix atmospheric nitrogen in forms available to plants.

On average, legume-based cover crop systems can contribute 40–150 kg of N to subsequent crops when the biomass is stored and incorporated into the soil.

Despite this, vegetable crops often need more nitrogen for optimal yields. In addition, maximizing soil nitrogen fertility through cover crops also requires that a significant amount of land be unused throughout the season – the area under crop production is reduced.

As for organic vegetable growers in the northeastern United States , they rely on some form of fertilizer to keep the farm profitable.

The presence of another important nutrient, phosphorus, is not uniform in soils. For example, phosphorus is scarce in the US Midwest, but abundant in some other areas.

In the state of Vermont, located in the northeastern United States, phosphorus is present in such high quantities that it is considered a potential pollutant on many farms. Dairy farming has been the state's main agricultural activity for over a century, and farmers have imported significant amounts of grain, primarily from the Midwestern states, to feed their cows.

From 1925 to 2012, Vermont farms annually accumulated more than 1,000 tons of excess phosphorus from livestock.

Manure from dairy cows is commonly applied to fields as a source of fertilizer because it is high in nitrogen, which supports regional production of corn and other field crops, including vegetables.

However, manure applications have historically been based on the nitrogen requirement of plants, although manure also provides a significant amount of phosphorus to the land where it is applied, and phosphorus accumulates over time and enters water bodies, causing the growth of toxic algae.

Organic vegetable growers must carefully consider the application of fertilizers to their crops, striving to balance productivity, costs, nitrogen and phosphorus regulatory limits, and taking into account the needs of their sites and soil types.

Meanwhile, sheep farmers in the Northeast US (New England) region are suffering from falling wool prices. Sheep shearing is a necessary procedure, regardless of whether it is wool, MEAT or dairy sheep.

Since much of the sheep's wool produced in the northeast is coarse and not suitable for value-added products that require softness, such as yarn or clothing, it is cheap.

Since 1994, the market price of raw wool has been falling and is now below the cost of shearing and transport. When they fail to sell, many store the wool in a barn or take it to the forest to a landfill.

There is a new use for low-quality wool specifically for organic farming, where growers have traditionally relied on animal manure: processing wool waste from factories or farms into fertilizer.

Benefits include soil conditioner functions to improve water-holding capacity, bulk density and other soil quality characteristics, and slow release of nutrients without the risk of environmental pollution with phosphorus or nitrate.

Polish scientists have recorded an increase in the yield of tomatoes, sweet peppers and eggplants grown on sheep wool boards, up to 33%.

Techniques for converting wool waste into useful fertilizer through hydrolysis have been developed to improve nutrient bioavailability, product processing, and remove contaminants found in recycled wool waste.

The lower N release rate helps avoid the risk of nitrate leaching and runoff before plants can use the nutrients. In addition, fifty percent of the weight of wool is carbon, and thus low-till pellets can also provide farmers with the opportunity to sequester carbon through fertilizer selection by incorporating wool pellets into the soil.

The key question here is whether the use of minimally processed wool pellets can increase the productivity of vegetable plants.

The study was conducted during the 2021 growing season at two sites in Vermont, located in the northeastern United States, at two sites. The first was located on a certified organic commercial vegetable farm in Orange County, where the soil was well-drained coastal silty loam and the planting history consisted of mixed vegetables, including an annual cover crop of winter rye.

The second site was located at the University of Vermont Horticulture Research and Education Center in Chittenden County on the Catamount Educational Farm's certified organic vegetable gardens.

The soil type in this area is lacustrine loamy sand with excessive drainage. The crop history is a two-year cycle of mixed vegetables, alternating with oats/clover (summer) or rye/vetch (winter) as cover crops, with the field covered for the entire previous year. This field was prepared with a low tillage system including disc harrowing of crop residues followed by a seed bed with a Perfecta field cultivator.

Each plot grew one bed of spinach (Kolibri variety) and tomato (Skyway variety). Both cultures were sown in a greenhouse for subsequent transplantation to the research site.

The primary variable in this study was the type and/or amount of fertilizer used to provide additional nutrition to each crop over and above that provided by the soil.

The wool pellets were obtained from Wild Valley Farms (Croyden, Utah, usa). The commercial fertilizer used in standard grower treatments was Pro-Booster 10-0-0 (North Country Organics, Bradford, VA, USA).

Pro-Booster is a blended granular fertilizer mix certified for use in organic production systems. Fertilizer is made from FLOUR with vegetable protein (such as alfalfa, cocoa, cottonseed, algae, peanut and soy flour) and animal protein flour (blood, crab shell meal, whey powder, feather and fish meal) plus pasteurized poultry litter and soda nitrate.

These sources, especially soda nitrate, which is the source of nitrates mined in Chile, as well as blood and bird droppings, are relatively fast-release forms of nitrogen, which distinguishes this product from the slower-release nitrogen found in woolen products.

In the pellet trials, one experiment was standardized for commercial nitrogen application with a "grow standard" and the second, proposed by the pellet manufacturer, suggested a higher level of nitrogen supplementation, about 2.5 times the standard. Plants in the control plots were not fed.

Overall, little difference was observed between treatments.

Both tomato and spinach yields tended to increase with increased fertilization without any difference between commercial and wool granular fertilizers applied at the same nitrogen rate.

The uptake of mineral nutrients by spinach plant tissues differed for K, Mg, P, S, B, and Ca, but there was no general trend that could be attributed to a particular treatment.

The quality of tomato fruits was the same for all types of treatment, the “starving” plants on the control showed a lower yield as expected in comparison.

The main nutrient that was clearly affected by the dose-response is nitrogen, which is found in large quantities in leaves fed with wool fertilizers. This suggests higher mineralization and/or uptake of nitrogen from wool sources compared to standard commercial organic fertilizers.

Overall, wool pellets are very similar to commercial organic fertilizers for both crops and could be a promising alternative for greater integration of plant and animal systems on diversified farms.”