Dr. Lee Manske – July 2011

In this months training we talk with Dr. Lee Manske, Range Scientist at North Dakota State University. Dr. Manske has been studying grazing practices and results for over 30 years. In this interview you will hear the 1 grazing strategy that has improved pastures and grasses out of the 36 Dr. Manske has studied. Dr. Manske says that most of us are missing 2/3 of our profits with our current grazing practices. Be ready to have your paradigm challenged with this talk with Dr. Lee Manske!

Address: Dickinson Research Extension Center
1041 State Avenue, Dickinson, North Dakota, 58601
Phone: (701) 483-2348 ext. 118
Email: Llewellyn.Manske@ndsu.edu
Employment: North Dakota State University 1975-present
Appointment: Research 100%
Research Rank: Range Scientist
Academic Rank: Associate Professor

Education: Ph.D. North Dakota State University, GPA 4.0, 1980.
Botany-Range Management, Department of Botany
Livestock Nutrition, Department of Animal Science

Publication: Refereed and Peer Reviewed Articles 65
Scientific Proceedings 62
Research Publications 205
Scientific Reports 564
Books 15
Popular Press 512

Scientific Oral Presentation: 50 to 60 per year, 65 in 2010.

Research Emphasis: Ecology of perennial grass defoliation
Manipulation of defoliation resistance mechanisms
Management of efficient forage nutrient capture
Biologically effective forage management strategies

Web Site: GrazingHandbook.com

What will Dr. Manske discuss?

I have been employed by North Dakota State University for 37 years, 1975 to present. I am naturally curious, and I enjoy solving complex problems. My education and training is ongoing and covers a wide spectrum of subjects. During my research career, I have worked primarily to solve two main problems: increase the quantity of new wealth captured from the land resources by livestock agriculture; and improve the health and production of grassland ecosystems. My topic for the Grassfed Exchange is how to manage livestock grazing to fully activate the defoliation resistance mechanisms in grass plants. I will describe how these processes work and what I have discovered.

My early grazing systems research conducted during the late 1970's evaluated the effects of 36 grazing systems on rangeland ecosystems and on prairie grouse habitat. From this research, I discovered that two grazing periods per pasture on three and four pasture rotation systems increased grass herbage biomass production. At that time, I did not know why or how defoliation by grazing stimulated grass production, but I knew that I needed to determine the operative processes. At first, I incorrectly tried to correlate the increased grass production directly with improvement in the carbohydrate content. Then, McNaughton found compensatory growth in grazed grasses, Coleman and crew described the relationship between rhizosphere organisms and perennial grasses, and Briske and crew improved the understanding of vegetative reproduction from axillary buds. Collectively, these processes became the Defoliation Resistance Mechanisms in perennial grasses. With the discovery of these important mechanisms, I was able to work on finding the how and the when that these beneficial mechanisms could be activated.

The rhizosphere organisms are limited by access to simple carbon chains because the microflora trophic levels lack chlorophyll and have low carbon content. Grass plants are known to exudate sugars, amino acids, glycosides, and other compounds through the roots into the soil. Partial defoliation at vegetative growth stages causes greater quantities of grass plant exudates to be released into the narrow zone of soil surrounding living roots. I have discovered that when grass tillers were partially defoliated between the three and a half new leaf stage and the flower stage, the rhizosphere volume increases greatly. The primary producer trophic level in the rhizosphere is comprised of fungi and bacteria. These organisms contain high proportions of nitrogen and they consume relatively large quantities of soil organic matter. The microfauna trophic levels graze on the primary producer organisms. The microfauna organisms excrete the excess nitrogen that they can not use as ammonium, which is nitrified into nitrate, a form of mineral nitrogen, by the rhizosphere fungi. The fungi then moves the mineral nitrogen into the roots of the partially defoliated grass tillers. Thus, with an increase in available carbon from grass plant exudates, the rhizosphere organism biomass and activity levels increase and a greater quantity of organic nitrogen is converted into mineral nitrogen that becomes available for use by the grass tillers.

The compensatory physiological processes within grass tillers are activated following partial defoliation at phenological growth stages between the three and a half new leaf stage and the flower stage. The growth rates of replacement leaves and shoots are increased. These increased compensatory growth processes require increased quantities of carbon and nitrogen. The source of the carbon is not from stored carbohydrates, but from increased photosynthetic capacity of remaining mature leaves and rejuvenated portions of older leaves not completely senescent. I have determined the quantity of leaf area required to provide adequate quantities of carbon to be 66% to 75% of the predefoliation leaf area. Which means the livestock can remove 25% to 33% of the grass tillers leaf area without detriment during the first grazing period. However, if 50% of the leaf area is removed by livestock during the first grazing period, the amount of remaining leaf surface is insufficient to provide the required quantities of carbon and the increased compensatory growth processes do not occur.

The source of nitrogen for increased compensatory growth of replacement leaves and shoots is not from stored nitrogen but is the mineral nitrogen in the rhizosphere that the microorganisms had converted from organic nitrogen. I have determined that a threshold quantity of 100 pounds per acre of soil mineral nitrogen needs to be available to the defoliated grass tiller in order for the increased compensatory growth processes to take place.

When 25% of the grass tiller leaf area is removed during the first grazing period, 140% of the leaf weight removed is replaced by the compensatory growth processes. When 50% of the grass tillers leaf area is removed during the first grazing period, only 70% of the leaf weight removed grows back.

There is one axillary bud for each leaf produced on a grass tiller. Most grass species produce six to eight leaves per tiller during the growing season. Development of the axillary buds into secondary tillers is inhibited by the hormone auxin, which is produced in the apical meristem and young developing leaves of grass tillers. Partial defoliation of lead tiller leaf material at growth stages between the three and a half new leaf stage and the flower stage activates vegetative reproduction of secondary tillers from axillary buds by temporarily reducing the quantity of auxin in the lead tiller; this permits the growth hormone cytokinin to stimulate growth of cells in multiple axillary buds. The growth of secondary tillers from axillary buds is dependent on the increased quantities of carbon and nitrogen from the same sources as the compensatory growth processes.

When 25% of the grass tillers leaf area is removed during the first grazing period, the quantity of secondary tillers increases 38% during that same growing season and increases 64% to 173% during the second growing season. When 50% of the grass tiller leaf area is removed during the first grazing period, the quantity of secondary tillers decreases 53% that same growing season and decreases 63% to 144% during the second growing season. Leaving 66% to 75% of the leaf area following grass tiller defoliation during the first grazing period and providing 100 pounds per acre of soil mineral nitrogen by the rhizosphere organisms are essential for the defoliation resistance mechanisms to be fully activated.

I have developed a 3 day workshop that instructs cow-calf producers on how to develop and properly operate a biologically effective management strategy with twice-over rotation grazing on summer pastures in conjunction with a complete 12 month complementary pasture and harvested forage sequence specific for his or her ranch. These science based management strategies meet the nutrient requirements of livestock during each production period, meet the biological requirements of grass plants and rhizosphere microorganisms, increase the quantity of forage nutrients produced, improve the efficiency of forage nutrient capture, and improve the efficiency of conversion of forage nutrients into saleable animal weight commodities. These biologically effective 12-month management strategies generate greater new wealth from the land natural resources without depleting future production. Information related to the workshop material is available at http://www.GrazingHandbook.com.

I am starting a new project that tests and evaluates forage management strategies that provide sufficient nutritional quality for calves to grow from weaning to finish with the produced meat reaching the highest quality grade and yield grade of the animals genetic potential at around 18 to 24 months of age with the costs per pound of weight gain at less than that of grain-fed beef.

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