Scientists had known from very early in the 1900's that Northern Plains grasslands managed by standard traditional practices were deficient in available mineral nitrogen.
The uninformed homesteaders that had not been provided the needed technology to properly manage Northern Plains grasslands implemented eastern practices that caused millions of grassland acres to deteriorate.
After World War II, low cost ammonium nitrate fertilizer became available. Application of nitrogen fertilizer to native grasslands was extensively studied at the ARS Stations at Mandan, ND and Sidney, MT and at the NDSU Dickinson Research Extension Center, ND.
The first couple of years of research with the application of various rates of ammonium nitrate to deteriorated native grasslands showed an increase of the long shooted grass species and some decrease of the short shooted grass species, which seemed to be exactly what these grasslands needed.
It did not take too long to show that the decrease in the short warm season grasses resulted in an increase in bare spaces which caused an increase in soil temperature and an increase in water evaporation. In addition, the nitrogen fertilizer caused a serious biological complication with the soil microbes causing a great reduction in their biomass and a loss of the ecosystem biogeochemical processes resulting in a great reduction in ecosystem functionality and a loss of native grass species.
Ten years of nitrogen fertilizer application caused a complete change from a native grassland to replacement grassland with a combination of smooth bromegrass, Kentucky bluegrass, and crested wheatgrass.
Northern Plains grasslands do not need additional nitrogen fertilizer applied to the soils. Intact grasslands contain a wide range of 3 to 8 tons/ac, with most land at 5 to 6 tons/ac of organic nitrogen that accumulated a few pounds per year over a period of 5,000 years (Brady 1974). Organic nitrogen is not available for plant growth. Organic nitrogen must be transformed by soil microbes to mineral nitrogen. Which means that Northern Plains grasslands were not short of nitrogen but were short of soil microbe biomass to transform the organic nitrogen.
Unfortunately, the soil microorganism information was unknown until the 1980's. Coleman et al. 1983, Ingham et al. 1985, and Clarholm 1985, described the rhizosphere organisms and the basic science of how they interacted and the biogeochemical processes they performed. With much regret, these basic scientists did not study the applied science aspects of how to increase their biomass and ways to increase their transforming processes to increase the soil available mineral nitrogen quantity.
Wight and Black (1972, 1979) had determined the threshold quantity of available mineral nitrogen needed to be at a minimum of 100 lbs/ac (112 kg/ha) in order for the precipitation (water) use efficiency mechanisms in grasses to function at biological potential. Manske (2010a, b) determined activation of the compensatory physiological processes and the asexual processes of vegetative tiller production in grass lead tillers also required available mineral nitrogen to be at 100 lbs/ac (112 kg/ha) or greater.
Manske (1996, 1999, 2018a) described the applied science aspects and the biologically effective grazing management practices needed to elevate the soil rhizosphere microorganism biomass enough for the microbes to transform a greater quantity of available mineral nitrogen. The rhizosphere biomass has to be a little greater than 214 kg/m3 in order to transform the threshold quantity of 112 kg/ha (100 lbs/ac) of available mineral nitrogen.
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