Pasture forage quality and yield response to irrigation, N fertilizer, and organic amendments

Final Report for LNE03-185

Project Type: Research and Education
Funds awarded in 2003: $69,852.00
Projected End Date: 12/31/2005
Matching Federal Funds: $157,329.00
Matching Non-Federal Funds: $13,871.00
Region: Northeast
State: Vermont
Project Leader:
William Murphy
University of Vermont
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Project Information


On the Forgues Family Organic Dairy Farm, near Alburg Springs, Vermont during 2003-2005 we studied pasture forage yield and quality under Voisin management-intensive grazing with treatments of irrigation or nonirrigation, and eight levels of soil fertility treatments (0, PKlime, NPKlime, fish, fish/seaweed, crab shell, and two levels of dairy manure compost). Compost, nitrogen, and irrigation increased forage yield, with compost providing the most beneficial effects on yield and forage quality. This research was used as a focal point to attract graziers to two pasture walks per season, to learn about the research and basic and advanced aspects of management-intensive grazing. Graziers learned techniques that help them either to begin using or improve their use and profitability of management-intensive grazing.


When all is said and done, what matters to farmers is “Does it pay?” To farmers trying to farm sustainably in ways that do not harm the environment the question becomes more complicated; besides money, the complex answer must involve long-term environmental and social issues.

This project relates directly to underlying crucial issues that we must face as a society: Where does our food come from and what are the consequences? Food must be produced locally as much as possible and in harmony with the environment and available resources. Otherwise, the food supply is precarious and probably not sustainable in the long term.

Unfortunately, most food for New England is imported, either from other regions of the United States or from other countries. Vermont is the largest dairy producing state in New England, but most of this production is done in year-round confinement based on high purchased inputs and tillage cropping of corn and alfalfa on erodible soil, and the raw milk is shipped out of state for processing. Even without considering the environmental costs of tillage cropping erodible soil, year-round confinement dairying is not sustainable, because cost of required inputs tends to increase, while value of the product (raw milk) tends to decrease.

Vermont has climate and soils well suited to livestock production on pasture. These same conditions, however, are poor for growing corn and alfalfa. It is too cold for corn and soils are too poorly drained for alfalfa. Corn silage yields generally are too low to pay economic production costs, without considering environmental costs of soil erosion and water contamination. Because of root diseases, alfalfa usually does not persist more than 3 years.

In areas such as Vermont that tend to have dry spells during the growing season, pasture irrigation should be considered as a way of consistently maintaining optimum production of high-quality forage. Indeed, the Northeast Pasture Consortium (representing all universities and USDA Agricultural Research Service facilities in the Northeast) listed pasture irrigation as a top research priority at its 2003 annual meeting.

To obtain the most benefit from adequate soil moisture, soil nutrients must not be limiting plant growth. On conventional farms it is relatively simple to apply fertilizers according to soil test indications. For organic farmers, however, little or no pasture data exist, other than testimonials, for the organic soil amendment products being marketed. We did this 3-year study to measure the effects of organic fertilizers and amendments with irrigation under Voisin management-intensive grazing.

Performance Target:

The outreach objective/performance target was to have 30 experienced graziers adopt at least two of these new practices: a) pre- and post-grazing pasture dry matter estimating, b) feed planning, or c) phenological timing of N fertilization; and have 10 inexperienced graziers begin using management-intensive grazing.

The research objective was to determine N fertilizer and organic soil amendment effects on forage yield and quality of irrigated and nonirrigated pasture under Voisin management-intensive grazing.


Click linked name(s) to expand/collapse or show everyone's info
  • Juan Alvez
  • Henry Forgues
  • Travis Forgues


Materials and methods:

This 3-year study began in 2003, on the Forgues Family Organic Dairy Farm, in Northern Vermont near Alburg Springs. The pasture had been cropped with corn and alfalfa for 17 years. Then it was
seeded down to a pasture mixture of grasses and legumes, and grazed for 9 years by dairy cows under Voisin management-intensive grazing.

The pasture sward was composed mainly of Kentucky bluegrass (Poa pratensis), orchardgrass (Dactylis glomerata), quackgrass, (Elymus repens, L.Gould), white clover (Trifolium repens), red clover (Trifolium pratensis), dandelion (Taraxacum officinale, Weber) and chickory (Cichorium intybus, LINN.)

The experimental site has an Amenia silt loam soil, with 3 to 8 % slope and moderately good natural drainage. The experiment was in the middle of a 1-ha area, away from fences, to avoid selective grazing of the experimental area and fence-line grazing effects. The irrigated treatments were in a 1.2-acre area that was also irrigated, to avoid selective grazing of the experimental area.

These treatments were applied in irrigated and nonirrigated blocks:

1. A total of 57 lb/acre of N was applied each year according to Voisin’s suggestions and N split-application results obtained in Prince Edward Island. We applied N as Chilean nitrate at 22 lb/acre in early spring when wild apple trees around the pasture had just begun to bud (phenological plant growth signal), 10 lb/acre in mid-June and early August, and 14 lb/acre in early September.

2. Neptune’s Harvest organic soil amendment products were applied as follows: hydrolyzed fish and fish/seaweed blend were applied at the rate of 3.5 qt/acre after each grazing. Crab shell was applied at 200 lb/acre once each spring before grazing began.

3. Mature 1-year-old dairy manure compost, produced on the Forgues farm by piling without turning, was applied after the first grazing in the Spring 2003 at 5 or 10 tons/acre, rates commonly used on this and other dairy farms in the area.

4. P, K, and lime were applied according to soil test recommendations in the PKlime and NPKlime plots. Organic amendments were applied only in the plots receiving them. Each fall, before applying fertilizers, lime, or amendments, soils were sampled in each B factor plot and analyzed by the University of Vermont Agricultural and Environmental Testing Laboratory.

Plots were irrigated when soil moisture was greater than 60 centibars, measured with an SDEC tensiometer. Irrigation was done at night under calm wind conditions, to avoid evaporation and watering patterns caused by wind. Amounts of water applied were measured using a standard rain gauge placed in the center of the plots. Daily precipitation at the site was measured using a standard rain gauge placed in the center of the plots.

We irrigated precisely by applying small amounts according to tensiometer measurements. Water was applied through irrigation sprinkler heads mounted on 18-inch risers on lateral lines of 1-inch diameter PVC tubing. Lateral lines were connected to 2-inch diameter main lines. A 5-hp gasoline-powered pump was used to provide 3.4 atm pressure from 36-ft radius heads, applying 3 gal/minute/head. Water was pumped from a nearby pond, applying 0.5 inches of water per application. This application rate was based on precision irrigation practices in New Zealand.

Pre- and postgrazing pasture mass (total forage present, measured from soil surface) was estimated using an electronic capacitance meter in 2003, and a pasture plate in other years. All plots and surrounding areas were grazed when the average forage mass within each factor A main plot reached 2400 lb DM/acre (6 inches tall). They were grazed down to 1000 lb/acre (1 inch tall) within 12 hours by approximately 100 lactating cows; the animals were then removed until the next grazing. Previous research showed that this grazing management resulted in highest forage yield.

Before grazing, two 4- x 36-inch forage samples were collected along a diagonal line at points chosen by systematic randomization within each B factor treatment plot, by clipping at soil surface with an electric clipper. One sample was separated into grass, legume, and forb components, dried at 50 °C, and weighed to determine forage yield and botanical composition. The other sample was analyzed by the University of Vermont Agricultural and Environmental Testing Laboratory for forage quality factors of dry matter (DM), crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), total digestible nutrients (TDN), and net energy lactation (NEL). After each grazing, the entire experimental area was clipped to 2.5-cm from soil surface so that subsequent measurements of forage were from regrowth, not rejected material from previous grazings.

The experimental design was a two-factor strip plot, replicated three times. A strip design recognizes the difficulty of randomization when dealing with factors such as irrigation and allows for the considerations of strips of blocks to be treated as replicates in the analysis.

Factor A main plots consisted of two levels of irrigation (irrigated or nonirrigated). Factor B (randomized within each A strip) received eight levels of fertility treatments (control; phosphorus (P), potassium (K), and lime; NPK lime; hydrolyzed fish; hydrolyzed fish and seaweed; ground crab shell; and two levels of dairy manure compost (5 or 10 tons/acre). Factor A strips were grouped to facilitate irrigation and achieve uniform water spray patterns from sprinkler heads in the irrigated treatment; the group was 40 x 60 ft.

Each factor B plot was 5 x 20 ft, to achieve the long, narrow sample area essential for accurate forage measurement. There were 24 nonirrigated and 24 irrigated plots replicated in three blocks of eight plots, respectively.

Research results and discussion:

During the first 2 years, only two people requested help with grazing management, and these were people who weren't presently farming, but wanted help in planning. In the second year, private grazing-management consultants objected to the project’s offer of free consulting. Since it interfered with their businesses, we stopped offering consulting, and relied only on the two pasture walks each year to provide information to people who were interested enough to attend.

Our original performance target turned out to be too optimistic. Only 25 farmers with grazing-management experience, nine inexperienced farmers, and seven agency people participated in the project by attending pasture walks. One of the main difficulties in getting farmers to change to a more profitable and sustainable farming practice such as grazing, seems to result partially from peer pressure against change. For example, some farmers who have switched to grazing, at first only grazed at night, so their neighbors and others wouldn't ridicule them.
Total 2003 forage dry matter yield (tons/acre) for nonirrigated and irrigated treatments, respectively, was: control 2.2, 2.7; PKlime 2.0, 2.5; NPKlime 2.8, 2.8; fish 2.1, 2.5; fish/seaweed 2.0, 2.5; crabshell 2.2, 2.5; 5 tons compost 2.9, 3.4; and 10 tons compost 3.2, 3.3. Average yield over all treatments was 2.4 tons/acre without irrigation and 2.8 with irrigation. Legume (red and white clover) content averaged 15% without irrigation and 17% with irrigation.

Winter kill due to ice sheets during the winter of 2004 decreased yield (average total = 1.9 without irrigation; 2.2 with irrigation) and clover content (decreased to about 5%) in all treatments. Forage yield increased in 2005 to an average of 2.5 tons/acre; most treatments (except compost) returned to or exceeded their 2003 levels. Since compost treatments did not return to their 2003 yield levels by 2005, it may indicate that compost's growth-promoting influence was no longer in effect. Legumes reestablished without reseeding in 2005 to levels equal to or above (average 22% nonirrigated, 24% irrigated) what existed before the winter kill.

This showed that pasture swards, with appropriate grazing management, can recover from winterkill without reseeding. Of course, it might not be possible for a farmer to forego normal forage yield for a year on damaged pasture while waiting for it to recover. This was the case on the Forgues Farm. All of their pastureland was so severly damaged that they had to reseed, using forage sorghum (spring barley or oats also could have been used) as a companion crop. This provided the needed forage for winter feeding, while seeding down perennial grasses and legumes for subsequent years' grazing. They used it as an opportunity to introduce new plant varieties.

Forage quality was fairly constant over all treatments during the course of the project, despite differences in legume content. This showed that with appropriate grazing management pastures produce high-quality forage. Crude protein averaged 19% in 2003, 17.5% in 2004, and 19% in 2005. Total digestible nutrients averaged 70.5% in 2003, 60% in 2004 (decline due to legume winter kill), and 68.5% in 2005. Net energy lactation (Mcal/lb) averaged 0.66 in 2003, 0.57 in 2004), and 0.63 in 2005.

Irrigation in a dry year (2003) increased pasture DM yield about 0.5 ton/acre, and legume content about 2%.

Although N fertilizer (as Chilean nitrate) increased forage yield as much as irrigation, it decreased forage quality, because N favors grass growth more than legumes. Legume content in the N treatment averaged 15% in 2005, the same as the average across all treatments in 2003. The decrease in legume content (1-8% decrease)of swards treated with N, besides economic considerations, makes the use of any N fertilizer less desirable than compost for improving pasture forage yield.

Fish, fish/seaweed, and crab shell had no positive effect on forage yield or quality.

Compost produced on the farm was the only soil amendment that increased forage yield in 2003. This is a happy result, since manure must be used on farms in ways that do not damage soils or pollute the environment.

Environment includes the air that people breath. The air around farms that store and apply liquid manure becomes extremely polluted and obnoxious to people living nearby. Also, soils are severly compacted by heavy equipment applying liquid manure.In addition, roads are damaged by the equipment. More than likely, this practice will not be able to continue indefinitely. Composting manure reduces or eliminates all of these problems, while conserving more of the nitrogen excreted by the livestock.

Compost had an equal or greater positive effect on forage yield as irrigation water did, compared to the control in 2003. Even without irrigation in a dry year (2003), compost increased forage yield 0.7 to 1.0 tons/acre, and increased legume content 4 to 11%, thereby improving forage quality.

By the third year of the experiment, grazing management increased legume content across treatments (except N) to an average of 23%. This was similar to the level reached in the high-compost treatment in 2003.

Participation Summary


Educational approach:

So far, research results have been published as a conference poster, a Master's thesis, in Vermont Grass Farmers newspaper (Solar Dollar), and as handouts at pasture walks:

Alvez, J. and B. Murphy. 2004. Irrigation, Nitrogen and Soil Amendment Affects on Pasture Forage Yield and Quality. Northeastern Sustainable Agriculture Research and Education Conference poster. South Burlington, VT.

Alvez, J. 2005. Irrigation, Nitrogen and Soil Amendment Affects on Pasture Forage Yield and Quality. MS thesis, University of Vermont. September.

Complete results will be published in a scientific journal and in other newspapers for farmers besides the Solar Dollar.

No milestones

Additional Project Outcomes

Project outcomes:

Impacts of Results/Outcomes

The farmers who attended the pasture walks learned a great deal and are extremely enthusiastic about feeding livestock on well-managed pasture. Their enthusiasm, prosperity, and happiness in farming based on permanent, well-managed pasture cannot help but influence their farmer neighbors. In the long run, as input costs increase and price received for product remains static or decreases, their neighbors inevitably will change to pasture-based farming or go out of business.

Economic Analysis

Hay (a substitute for pasture forage) currently sells for $200/ton, delivered, in Vermont. Pasture forage has a higher quality than hay, so it is worth more and also costs less to feed than hay. Since this pasture forage was certified organic, it was worth more than common forage.
The control (no treatment) produced an average of 2 tons forage/acre. This had a gross value of $400/acre.

The 0.5 ton/acre of increased forage from irrigation had a value of $100/acre. Irrigation was only needed 1 out of 3 years, so it is unlikely that it would be profitable to irrigate at this site. Depending on costs, irrigation might be profitable at other locations.

Feeding hay requires more grain supplementation than pasture to achieve equivalent levels of production. Grain is produced in tillage cropping, which results in more soil erosion and more pollution of surface and ground water with nutrients and pesticides than pasture does. So irrigation might help reduce environmental pollution due to tillage cropping.

Costs of irrigating vary greatly, depending on source of water, equipment and labor cost, and fuel or electricity cost to run pumps. Each farm is unique, requiring individual analysis to determine if irrigation potentially would be profitable. Irrigation is not needed if rainfall is adequate, so long-term rainfall patterns need to be considered in deciding to install irrigation equipment.

Although N fertilizer increased forage yield as much as irrigation, it decreased legume content. Chilean nitrate currently costs about $765/ton and is expected to become more expensive as transportation costs increase. The amount of fertilizer used in this study cost about $120/acre. This expense makes use of Chilean nitrate on pasture unprofitable.

Fish, fish/seaweed, and crab shell had no positive effect on forage yield or quality.

Compost produced on the farm (no turning) was the only soil amendment that consistently increased forage yield and legume content. Compost had an equal or greater positive effect on forage yield as irrigation water did. Even without irrigation in a dry year (2003), compost increased forage yield 0.7 to 1.0 tons/acre. In terms of hay price, this increased yield would be worth $140 to $200/acre! Therefore, compost answers the farmer’s question, “Does it pay?”, with an unqualified: “Yes!”

Farmer Adoption

Twenty-five farmers with experience in management-intensive grazing attended one or more of the pasture walks at the Forgues Farm. Nine farmers new to grazing management attended the walks. Seven people from federal, state, and university agencies attended the walks.

During the pasture walks they learned about intensifying grazing management, irrigating, and applying nitrogen and organic amendments to increase forage yield and quality. They also learned about using forage sorghum as a companion crop to produce much-needed forage and simultaneously reseed perennial grassses and legumes. This was done on the Forgues Farm during the 2004 growing season, due to the winter killing of pastures in the previous winter.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

No areas of grazing management need additional study at this time. We know how to manage pasture well for profitable livestock production with minimal or no environmental harm. Information on how to do it exists for those who care to look. What's needed is to apply what we already know. Later, when farmers are using what is now known, further research might be needed to refine grazing management.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.