Nutrient Availability From Grassland

Grasslands

Discuss about the Nutrient availability from Grassland.

The ecosystem that is dominated by the grass-like plants such as sedges and rushes and vegetation are called the grasslands. The grasslands are distributed throughout all the regions of the world except Antarctica. It is estimated that about 25 to 40 percent of the Earth’s lands are covered with the grassland areas. The grasslands are broadly divided into temperate and tropical. The temperate grassland is found in the zones of the cold winters and warm-to- hot summers. They are the soils of huge fertility. However, the plants found in the temperate regions are often nutrient limited. The reason behind this is most of the nitrogen available in the soils cannot be utilized by the plants (Leff et al, 2015). When the plowing disrupts the the soil then the nutrients can be made available to the soil. Grasslands are the ideal candidates for crop production owing to high soil fertility and gentle topography. Tropical grasslands, on the other hand, have warm and dry climatic conditions and are often pronounced with the wet and dry seasons. The soils of the tropical grassland are less fertile than the temperate soils. This is due to the reason of the high amount of rainfall that the regions receive. Most of the shrubs and trees are found with high density in the tropical areas (La Pierre, Joern & Smith, 2015).

The carbon biomass and the ecosystem in Vertisol are regulated by herbivory and the nutrient composition. Vertisol is the soil which has the high content of clay known as the montmorillonite. The soil forms deep cracks over the years. The natural vegetations of the vertisols are grassland, savanna. The heavy texture of the soil makes the soil unstable for the growth of plants and crops.

It has been shown that the herbivory influences the source of carbon from the vertisols of the savanna grasslands. The nitrogen and the phosphorus are the major nutrient source from the vertisols of tropical grasslands. In Africa, the key determinant of the plant productions and the maintenance of the nutrients level of the vertisols is the rainfall. Grazing can reduce the carbon content of the grasses but enhances the organic matter and the nutrient content. Grazing can improve the quality of the grass by increasing the foliar N and the P. The herbivory accelerates the nutrient cycling and stimulates new shoots regrowth. The natural nutrient cycle is facilitated with the fecal matter deposition can increase the overall nutrient content of vertisols. Thus it is observed that high percentage of the nutrients consumed by the animals while grazing is cycling process. The N of feces does not get volatilized easily in the deposition.(Patel, 2014). P cannot be volatilized easily because of the bad quality drainage system in Vertisols. Thus are less available to the plants. The phosphorus can be made available with the reduction of the absorption into the clays. Increased P uptake will help in more in a regeneration of the tissues of the plants. Thus the foliar N:P content determines the nutrient availability of vertisol for the biomass. The lower N:P ratios of the grassland suggest that the productivity of the open grasslands in tropical areas are in short of nitrogen. While under trees are found in the limitation of phosphorus (Hobbie, 2015). The vegetation growth is not only influenced by the availability of nutrients but alongside mainly requires the water. Mainly the nutrients CO2 and water increase the overall productivity of the soils. The tropical grasslands are more subjected to water stress due to open grasslands for which even if the high amount of nutrients available they cannot be used by the plants (Vourlitis et al, 2015).

Grasslands of the Vertisols

It is already known that the nitrogen source which highly present in the soil can only be made available by plowing (Bardgett, Mommer & De Vries, 2014). There are substantial sources of carbon that can be sequestered in the temperate grassland and can only be found deep below the ground of roots and soil. Good source of carbon is obtained from these grasslands. The deep plant roots of plants in vertisols offer rhizodeposition resulting from the exudation, mucilage formation and the sloughing from the animals. Moreover, these are the reservoir for rhizosphere. Thus the soil nutrition in the vertisols is determined by the plant tissue chemistry, the C: N ratio and the C4 grasses and the not native rhizomatous C3 grasses. The C4 plants show highly slow nitrogen mineralization and the native C3 plants have increased in the rate of the N mineralization (Siebenkäs & Roscher, 2016). Thus the vegetation present there itself maintains the carbon pool of the grasslands because of photosynthesis by plants. The nutrients are also made available due to the soil microorganisms present. The temperature there is the main reason behind the soil organic nutrient availability. The vegetation is very rich and the soils are highly fertile due to the package of the roots with rhizomes. The soil is available for rich source of phosphorus, potassium, nitrogen, sulfur, calcium and iron (Mulligan et al, 2014) .

Vertisol grasslands are mainly not suitable for the nutrient uptake. It can be increased artificially to use it for the agricultural purpose. Sequestration of carbon can increase the overall nutrients of the soils. The biological processes that can increase the nutrient availability of the soil are by the accumulation of above and below ground litter, plant rhizodeposits and by products from the decomposers (Hulugalle et al, 2017).

The grasslands of vertisols are the good source of agriculture, alternative agriculture. There are various biological, chemical and physical processes that maintain the management of the center of nutrients in the soil. The essential nutrients can be available with the nutrient cycling. There are the huge amount of minerals required to maintain the growth and development of the vegetation. There could be nutrient rich sediments from the erosion makes the increase in nutrients in the grasslands areas. The weathering of the soil minerals also increases the availability of the micronutrients. The decomposers present there also plays a role in the recycling of the biomass and the decomposition that helps to enhance the organic matter contents which in turn increases the organic nutrients in the soils. The nutrients are also available in different conditions.  They could be soluble, readily available or weakly bound forms. The following diagram shows the different ways the nutrients are available in the grasslands.

 

Figure 1- The different ways by which nutrients in soil available to plants

(Source- Mulligan et al, 2014)

The grasslands are also not free from the depletions of the availability of the nutrient pools from the soil. These include the forest fire, overgrazing, loss of nutrients in the water which is due to excessive rain, erosion, leaching. There could be the primary loss in the nutrients due to gaseous losses to the atmosphere (Lehmann & Joseph, 2015).

References

Bardgett, R. D., Mommer, L., & De Vries, F. T. (2014). Going underground: root traits as drivers of ecosystem processes. Trends in Ecology & Evolution, 29(12), 692-699.

Hobbie, S. E. (2015). Plant species effects on nutrient cycling: revisiting litter feedbacks. Trends in ecology & evolution, 30(6), 357-363.

Hulugalle, N. R., Strong, C., McPherson, K., & Nachimuthu, G. (2017). Carbon, nitrogen and phosphorus stoichiometric ratios under cotton cropping systems in Australian Vertisols: a meta-analysis of seven experiments. Nutrient Cycling in Agroecosystems, 107(3), 357-367.

La Pierre, K. J., Joern, A., & Smith, M. D. (2015). Invertebrate, not small vertebrate, herbivory interacts with nutrient availability to impact tallgrass prairie community composition and forb biomass. Oikos, 124(7), 842-850.

Leff, J. W., Jones, S. E., Prober, S. M., Barberán, A., Borer, E. T., Firn, J. L., … & McCulley, R. L. (2015). Consistent responses of soil microbial communities to elevated nutrient inputs in grasslands across the globe. Proceedings of the National Academy of Sciences, 112(35), 10967-10972.

Lehmann, J., & Joseph, S. (Eds.). (2015). Biochar for environmental management: science, technology and implementation. Routledge.

Mulligan, A. A., Luben, R. N., Bhaniani, A., Parry-Smith, D. J., O’Connor, L., Khawaja, A. P., … & Khaw, K. T. (2014). A new tool for converting food frequency questionnaire data into nutrient and food group values: FETA research methods and availability. BMJ open, 4(3), e004503.

Patel, S. (2014). Integration of nutrient inputs on rice yield, nutrients uptake and availability in a vertisol (Doctoral dissertation, JNKVV).

Siebenkäs, A., & Roscher, C. (2016). Functional composition rather than species richness determines root characteristics of experimental grasslands grown at different light and nutrient availability. Plant and soil, 404(1-2), 399-412.

Vourlitis, G. L., de Almeida Lobo, F., Pinto, O. B., Zappia, A., Dalmagro, H. J., de Arruda, P. H. Z., & de Souza Nogueira, J. (2015). Variations in aboveground vegetation structure along a nutrient availability gradient in the Brazilian pantanal. Plant and Soil, 389(1-2), 307-321.