BY ALAZAR SHIFERAW
It quite clear that the agriculture sector in Ethiopia is supporting the livelihood of over 80 percent of the Ethiopian population estimated nearly over hundred million. Hence, to feed the growing population of the country, the need to increase production and productivity is highly pivotal; increasing per unit area productivity should be highly underlined. Thus, facilitating plant nutrients supply will enhance crops growth and development.
Increasing productivity has to be facilitated through adequate and
balanced supply of crop nutrients. Because declining soil fertility is a
serious problem to crop production and food security.
Applied and Environmental Science Journal said that emerging research outcomes from various parts of Ethiopia demonstrated alarmingly low Soil Organic Matter (SOM) and deficiencies of essential nutrients such as nitrogen (N), phosphorus (P), potassium (K), sulfur (S), boron (B), and copper (Cu) as the main causes of crop yield decline and no sustainable agricultural production.
The problems are accredited to continuous cropping of the same land year after year, inadequate replenishment of the lost nutrients, complete residue removal from the field, and soil erosion. To curb the soil nutrient depletion, fertilizers, like, organic, inorganic, or their integration are used as the source of essential plant nutrients.
Bijay Singh and John Ryan from Research Gate said that soil types vary widely throughout the world, depending on location (geology, climate, vegetation) with corresponding variation in the combination of physical, chemical and biological properties that support agricultural crops.
Soil fertility, or the soil’s reserve of crop nutrients, is broadly equated with soil quality and soil health. A fertile soil is a productive soil if growing conditions are favorable, e.g. adequate soil moisture and aeration, neither too hot nor too cold for crop growth, it said.
As soils vary in fertility, few can sustain high crop yields indefinitely without application of nutrients. For economic yields required in today’s agriculture, nutrients have to be added to the soil as mineral fertilizers and/or organic manures. Prior to the modern era of commercial agriculture, modest yields were achievable by adding organic manures, adopting crop rotations with legumes, or resting the land.
The amounts of major nutrients added in fertilizers must be based on what is already in the soil and what is removed in the crops. Fertilizer use efficiency implies the extent to which added nutrients are taken up by the target crop. In the case of N, efficiency is rarely above 50 percent, leading to losses from the field and potential negative impacts on the environment; current research is aimed at improving efficiency. Fertilizer use efficiency can be improved by adopting fertilizer best management practices.
However, mineral fertilizers are indispensable to ensuring food security for the world’s population of over 7 billion people. That dependence will be even greater in the future as the population increases and with increased affluence in some countries, it said.
Fertilizer use is also likely to increase with expansion of farming to less fertile areas as a result of competing demand for land use, as well as negative consequences of climate change. The sustainable use of fertilizers for mankind will have to be based on sound scientific principles and practices, the research indicated.
Historically, where soils were fertile and capable of producing adequate crop yields, and where there was enough water, either as rainfall or irrigation, civilizations flourished. In the past century, world food production increased dramatically due to enhanced crop yields as a result of widespread adoption of technologies such as mechanization, new high-yielding and disease-resistant crop varieties, irrigation, and especially the use of mineral fertilizers.
Thus, the current focus in soil and crop management is on maintenance of soil quality or soil health. Low or unbalanced fertilization leads to depletion of soil nutrients and degradation due to lower SOM contents from lower root biomass associated with reduced crop yields, and indirectly reduced soil structure which promotes soil erosion.
Equally, regular adequate fertilizer use is associated with small but consistent increases in SOM as a result of increased root biomass, despite the popular misconception that N use leads to decreased SOM. While fertilizer use has been associated with reduction in some soil organisms, these effects are relatively short-lived and only at the site of the fertilizer band.
Significant increases in microbial biomass have been shown by long-term application of fertilizers in non-acid soils. Transformation of ammonium-based N fertilizers in soils can adversely affect soil health by increasing acidity. The extent, to which this natural microbial-mediated process can impact the soil, and thus crop growth, is dependent on the form and amount of N applied and the soil’s, it said.
At Texas A & M University, Orgata, a study conducted on Soils and Fertilizers by V. A. Haby, Marvin among others stated that there are 20 essential chemical elements known to be required for normal vegetable growth. These elements can be supplied by either organic or commercial inorganic fertilizers. Carbon, hydrogen, and oxygen from air and water, and nitrogen from organic and inorganic sources are four plant nutrients which make up 95 percent of plant solids.
Although he atmosphere consist of 78 percent nitrogen as N2, this form is unavailable for plant use. However, certain bacteria that live symbiotically in nodules on the roots of legumes are able to take nitrogen from the air and fix it in a form available to plants.
The other 16 essential elements, iron, calcium, phosphorus, potassium, copper, sulfur, magnesium, manganese, zinc, boron, chlorine, molybdenum, cobalt, sodium, silicon and vanadium, are supplied to plants by the soil. With the exception of nitrogen and phosphorus, most alkaline, clay type soils usually contain enough of these elements for vegetable production. In acid sandy soils, nitrogen, phosphorus, potassium, calcium, magnesium and, at times, sulfur and boron may need to be added for successful crop production. Cobalt, sodium, silicon, and vanadium have been proven essential for only a few plants.
Oregon State University said that most of the time, the average person treats the soil “like dirt”. A wise farmer/rancher will care for the soil because he knows that man is dependent on the top 6 inches of soil. In the plant-animal-soil continuum, soil is often neglected because it does not indicate stress in an obvious way. Animals and plants show physical symptoms but the soil must be looked at more carefully to monitor good health.
Soil that is rich in nutrients is fertile. The expectation of growing plants as food for livestock must include the reality that plants will take nutrients out of the soil. Replacing nutrients is the basic goal of fertilization. Improper fertilization in the past has caused controversy, but the basic premise of fertilization is to replenish the soil.
Soils feed the plants which in turn feed the animals that feed us. Including soil in this important chain will help guarantee its success. Soil provides the support or foundation for plants and most of the nutrients. Soil is accumulated decomposing plant and animal matter with aging parent material. As the soil components break down, elements are released and become available to plants as nutrients.
However, naturally this process takes a long time and the soil will only be a result of the parent material, climate, those living organisms once living there, topography, and time. So what is made available to a plant at a certain time may not be exactly what a growing plant needs. Fertilization is supplementing the existing soil with additional, needed nutrients. Fertilizing wisely increases yield, quality (nitrogen content and digestibility), and profits.
Fertilization is an important issue because it is needed in order to produce enough food for the increasing population from the decreasing cultivated land, but too much or inappropriate use can be detrimental to the environment, it said.
The Ethiopian Herald April 24/2021
