Amending pasture soil to decrease weed presence while improving forage species composition and quality
Many farmers in the Northeast have pastures or hayfields that, over time, tend to show a decline in desirable forage species and quality as weed species increase. Common practice for pasture renovation includes mechanical cultivation, reseeding, and sometimes the use of herbicides, resulting in greater soil erosion and compaction, higher costs, and compromised natural resources. Recognizing that weeds thrive in particular conditions of low soil fertility, three one-acre test plots were amended with custom formulated blends to address mineral deficiencies, and compared to three adjacent one-acre control plots. As soil nutrition in the field increased, an increase was observed in palatable forage species, such as fescue, orchard grass, quackgrass, timothy, red clover, and vetch. A decrease was observed in broadleaf weed species including aster, buttercup, chickweed, cinquefoil, goldenrod, hawkweed, daisy, strawberry, and yarrow. Forage species were also sampled and analyzed for nutritional content to compare forage quality in test and control plots, though minimal differences were observed in plant tissue analysis, with the exception of higher boron levels in the experimental plots.
This study is taking place on Zephyr Hill Farm, which consists of 130 acres of fields and woodlands in Waldo County, Maine. The farm includes three acres of organically managed vegetables with integrated flowering, fruiting, and medicinal perennial species, approximately twenty acres of pasture, and over one hundred acres of woodlands. Singing Nettle Farm operates on this land, working with a team of Haflinger draft ponies to grow produce for a CSA (community supported agriculture) program, local restaurants, the Maine Organic Farmers and Gardeners Association (MOFGA) Common Ground Fair, and a farmers market.
This study was conducted during the 2011 and 2012 growing seasons in mid-coast maine on a six-acre section of pasture arranged in a randomized complete block design, consisting of three replications of one acre test plots and three replications of one acre control plots. Initial soil tests were obtained from each plot in spring 2011 to determine starting fertility levels and were repeated in spring 2012 to monitor progress and to make necessary nutritional adjustments.
Species composition was measured in each plot using the beaded string method (Northeast Cover Crop Handbook, Sarrantonio 1994), in which a string marked in three-foot increments is stretched across the plot in transects and the researcher records which species is growing beneath each mark. Weed and forage species composition were measured two times throughout the growing season: in June during first-cut (of hay), and again in September during second-cut. To measure forage quality, plant tissue samples from each plot were collected twice throughout the growing season, once in June and again in September.
Plant tissue samples for nutritional analysis were obtained by cutting every tenth plant (whether a weed or forage species) along the beaded string and bulking the cuttings as a representation of the entire plot. After plant sampling, all plots were mowed to simulate grazing and to prevent weed species from going to seed.
The soil tests revealed deficiencies in calcium, magnesium, phosphorus, potassium, nitrogen, sulfur, boron, zinc, copper, and manganese. Approximately 2,900 lbs of amendments per acre were spread on the three experimental plots with a drop spreader pulled behind a tractor in July 2011. The remaining three control plots did not receive any amendments. The amendment recipe included hi-cal lime, gypsum, soft rock phosphate, magnesium sulfate, sulfate of potash, manganese sulfate, dolomitic lime, sul-po-mag, humates, zinc sulfate, sodium nitrate, myco-seed treat, and copper sulfate. In 2012, an additional application of limestone, marl, sulfate of potash-magnesia, humus, soft rock phosphate, gypsum, brown phosphate rock, calcium borate, copper sulfate, zinc sulfate, and humates was applied at a rate of 1,000 lbs per acre. All ingredients in the blends were selected to meet USDA organic certification requirements.
Two complete growing seasons of data have now been collected for soil fertility, species composition, and plant nutrition. In September 2012, Singing Nettle Farm hosted an on-farm presentation of this project, drawing farmers from across the state and faculty from Unity, College.
Impacts and Contributions/Outcomes
Soil tests in 2012 indicated an increase in Ca, Mg, S, pH, conductivity, and P levels, with a slight increase in N and K in amended plots when compared to the control group. Species composition analysis in both June and September of 2012 indicated an increase in fescue, orchard grass, quackgrass, timothy, vetch, and red clover in the amended plots, as well as a decrease in aster, buttercup, chickweed, cinquefoil, goldenrod, hawkweed, junegrass, daisy, strawberry, and yarrow when compared to the control plots (Table 1). All species that demonstrated a decrease in the pasture thrive in conditions of low calcium, and many of those species also favor low phosphorus environments. Comparatively, species that showed an increase thrive in soils with higher Ca, Mg, S, P, and pH.
Nutritional analysis included nitrogen, phosphorus, potassium, calcium, magnesium, aluminum, boron, copper, iron, manganese, sulfur, and zinc levels, but showed no major differences between amended and unamended plots, with the exception of elevated boron levels in the amended plots.
Increased fertility in the amended plots demonstrated a correlation to an increase in some palatable forage species and a decrease in some non-palatable species. Weed species that thrive in soils with low Ca and low P showed a decrease in overall field composition after the addition of an amendment blend containing Ca and P. Palatable forage species that thrive in soil conditions high in Ca, Mg, S, and P demonstrated an increase in overall field composition after the addition of Ca, Mg, S, and P. While some change was observed in the forage species composition of the pastures studied, weed species are still present and soil fertility levels are still low to moderate.
In September 2012, Singing Nettle Farm hosted an on-farm presentation to allow other farmers to come and see the demonstration plots. Bill Errickson and Mark Fulford spoke about the project and the importance of proper soil nutrition on herd health. An off-site presentation in Unity, Maine and hosted by the Maine Farmland Trust is scheduled for January 2013 and will complete the outreach component of this project. Farmers’ feedback from the September presentation reinforced the need for low-cost, fast-acting solutions to the challenges of declining pasture fertility, which may be achieved with the use of liquid amendments in conjunction with a dry blended application. Future research is essential to discover the further effects on forage species composition of increasing soil fertility levels to maximum capacity.