Increasing the Sustainability of Dairy Farms by Improving Persistence of White Clover in Pastures
White clover in northeastern dairy pastures is known to improve forage quality and yield and decrease or eliminate the need for nitrogren (N) fertilization. Unfortunately, white clover survival can be a problem. This project conducted field trials to determine the seasonal growth pattern and times of stress for white clover in grazed pastures as well as the effect of moderate and heavy grazing pressure on white clover performance.
* The overall objective was to increase the sustainability of dairying and pasture-based agricultural systems in the Northeast through better management of white clover, a key pasture species.
* Detail the seasonal growth pattern of white clover in order to understand when it is most vulnerable and how it survives the stresses of pasture.
* Evaluate alternative varieties (cultivars) in terms of productivity and persistence.
* Test different grazing managements for effects on the first two objectives.
* Distribute information about the pasture ecosystem and superior white clover varieties to farmers who could make better use of pastures.
White clover in the Northeast is most vulnerable and most stressed in the summer, especially after drought.
Current recommendations for orchard grass-white clover pastures are about optimal.
Farmers making pasture seedings should be experimenting with improved white clover cultivars, especially those with virus and drought resistance. With pasture renovation costs calculated to be about $40 an acre, finding and growing better white clovers is economically sound.
Overgrazing of orchard grass may encourage weed encroachment into pastures.
Methods and Results
Field trials were conducted on Tom Miller’s dairy farm at Dryden, New York from 1993 to 1995 to determine the seasonal growth pattern and times of stress for white clover in grazed pastures as well as the effect of moderate and heavy grazing pressure on white clover performance. About 45 dairy cows were rotationally stocked on 50 acres of orchard grass-white clover pastures that were seeded in 1988. The soils are Phelps and Howard gravelly loams on rolling topography with moderate-to-good drainage. The climate is typical of central New York state.
From 1994 to 1997, white clover cultivars and experimental lines were evaluated under grazing on the Miller farm and at the NRCS Plant Materials Center at Big Flats, New York. From 1996 to 1998, Cooperative Extension information describing the pasture ecosystem was prepared as a basis for improving farmer and student understanding of pasture management. Finally, in 1997 and 1998, enterprise budgets of pasture renovation with improved white clovers were prepared to summarize the economic implications of the field work.
The ecological summary of this work identified five principles that can be demonstrated in a typical pasture in the Northeast: 1) everything that is organic is food (energy flows), 2) nothing is wasted (matter circulates), 3) there is a premium on protecting the soil, 4) there is always a substitute (biodiversity), and 5) there are always animals under natural conditions. These principles can be applied to good pasture management as well as general education about the ecological basis of sustainable agriculture.
The seasonal growth pattern of white clover in rotationally grazed pasture showed levels of leaf density and bud activity to be relatively low in the spring but increasing through the season. Mortality of complete white clover plants was very low throughout the season, although stolon decay and break-up into separate plants was observed. White clover plants were not smaller or less complex in branching pattern in the spring than later in the season. However, at the end of a hot and dry period in the summer of 1995, white clover plants occupied a smaller area and were less complex than plants in the spring. This contrasts with studies in milder climates where plants were smaller and less complex in the spring.
Reduced size and complexity is interpreted as a response to stress. Thus, summer drought appears to be the most important stress for white clover in our climate. We recommend that farmers decrease grazing frequency and closeness for a short period after a summer drought in order to maintain the productivity and persistence of white clover.
In contrast to white clover, the leaf-density and tiller-density of orchard grass and bluegrass decreased toward the end of the growing season. After the drought period of 1995, the leaf density of dandelion and other weeds was higher than they had been in the spring.
The most widely sown white clover cultivar in the Northeast is ‘California Ladino’ (or simply ‘Ladino’). Winter survival often has been associated with place of origin and increased stolon production. Thus we compared ‘Ladino’ to cultivars that were supposedly more stoloniferous or came from a colder climate. Twelve cultivars and breeding lines (including ‘Ladino’) were also established with orchard grass in ungrazed research plots at the NRCS Plant Materials Center at Big Flats, New York in 1995. The results do not clearly identify a cultivar better than ‘Ladino’. However, they do show there is a good possibility of improving this species by giving it more productivity in dry summers and increasing its resistance to virus diseases. Those changes would improve pasture yields and forage quality and reduce the risk of low pasture production.
Survival and recovery of white clover following summer drought was identified as an important problem. Increasing grass tiller density by more frequent spring grazing has helped reduce summer stress in white clover under conditions in New Zealand. Apparently, the increased shading and lower soil temperatures help during summer drought. The work in New Zealand was done with perennial ryegrass as the companion grass species.
Grass tiller density is known to show an inverse relationship with tiller mass. Thus, more frequent or closer grazing should increase tiller density. In 1993 we tested this hypothesis with orchard grass by grazing the test plots every seven days, which was about three days ahead of the farmer. In 1994 and 1995, we grazed at a starting pasture mass of 2100 kg/ha compared to the farmer’s starting mass of about 2400 kg/ha. The different grazing systems were applied only through June.
Our results showed that we did not increase orchard grass tiller density. In fact, the most aggressive system in 1993 appeared to weaken the orchard grass and allow weed invasion of the test areas. White clover leaf numbers were increased by more aggressive grazing, and following the 1995 summer drought, white clover recovered more quickly on the plots that had been grazed more frequently in the spring. Orchard grass is apparently weakened by grazing before it has about 2400 kg/ha of available forage. This weakening can benefit white clover if it is stressed by drought, but one must manage to optimize the pasture, and not just one species. We concluded that the present recommendations for grazing white clover and orchard grass pastures should not be changed.
Many of the practices of sustainable agriculture can be understood and refined in terms of ecological principles. In fact, some have argued that the way to make agriculture more sustainable is to make agroecosystems more like natural ecosystems. The grazed pasture is a relatively natural agroecosystem. We prepared a publication, “Concepts of Sustainability and the Pasture Ecosystem,” which identified five ecological principles that can be demonstrated in a typical pasture in the Northeast.
The definitions of sustainable agriculture, the pasture food web, the biomass pyramid, the carbon cycle, and species composition are presented for new as well as experienced visitors to the pasture ecosystem. The publication has been used with a laboratory field trip for the introductory course in sustainable agriculture at Cornell University.
The economic questions raised by the field work in this project boil down to the costs and benefits of improving the white clover component of orchard grass pastures in the Northeast. Our results indicate that reseeding improved cultivars may be more successful than attempting to refine the grazing management system. Thus we prepared enterprise budgets for pasture improvement including reseeding. We did not collect data on the likely responses, but have chosen to look at cases where such practices would increase yields by 1 or 2 tons per acre with 1.5% higher crude protein and 5% less neutral detergent fiber than the unimproved pastures. Those numbers are consistent with results from other studies done by NRCS or that have been reported in the literature. The Cornell FORVAL model was used to calculate the value of the pasture produced, given its forage quality and the market prices of alfalfa and timothy hays that would be used to replace the pasture should it not be available.
Two scenarios were considered: low feed prices ($100 a ton for alfalfa hay) and high feed prices ($200 a ton for the same hay). At low feed costs, increasing the yield and quality of a northeast pasture by planting an improved white clover cultivar would increase the value of the pasture produced from $120 to $130 an acre. With the expense of renovation being about $40 an acre, pasture reseeding would be a profitable practice.
Reported June, 1998. 1999 Northeast Region SARE/ACE Report.