Fertilizers have given new hope to the world for producing large quantities of food to fight the challenges of food security. Besides, they support the environment by less land use against high production. There can be some harm for both humans and the environment when the growers overuse fertilizers, whether nitrogenous or phosphatic irrespective of their chemical and organic nature. The excess always washes away from the system through leaching, evaporation, or surface runoff that pollutes the natural environment.
Fertilizer needs for growing different crop plants vary according to the soil type, climatic conditions, and irrigation techniques. It is necessary to fertilize plants according to their requirements during critical growth stages, whatever the soil type and climatic conditions prevail. Heavier soils need less fertilization than sandy soils, whereas the latter require more frequent irrigation than heavier soils.
Nitrogen deficiencies can be described as the reduction of the number of tillers or leaflets in plants which, gives rise to smaller canopies compared with those receiving their optimum supplies. Whereas the overuse of Nitrogen results in awkward dark green foliage with clawed-shaped leaves having unusual shine. In such conditions, the tips of the leaf often turn downwards like a fingernail, and the curve appears cup-shaped.
A typical pale green foliage with such symptoms is a good case of overuse of nitrogen in crop and fruit plants. Often such leaves turn yellow and drop from the plant. Phosphorous deficiency turns the top foliage dark green, and the lower foliage becomes purple. While, Potassium deficiency shows several symptoms, including shortening of stems, delayed flowering, yellowing of the mature leaves, and reduction in fruit and grain sizes simultaneously.
Similarly, some symptoms are related to minor fertilizer deficiencies. Calcium deficiency often causes bud rot or bud blasting besides cracking the spikes. Magnesium is responsible for causing interveinal chlorosis in the older leaves, and Iron deficiency causes chlorosis in the new leaves. Boron deficiency produces malformed leaves, stunted inflorescences, and cracks in the leaf margins.
All fourteen nutrients essential for crop growth are supplied through different means or derived from the soil resources. Out of these, 6 fall in the macronutrients and the other 8 in the micronutrients category. The application of the macronutrients on the crops is generally in heavier quantities, but the micronutrients are in smaller amounts. However, their role in crop growth and development is decisive, and their deficiency could lead to heavy production losses.
Since the functions of both macro and micronutrients are well determined in the process of crop growth, it becomes critical to calculate what numbers would essentially help optimum crop growth. Moreover, the absorption of micronutrients from the soil profiles, and the additives also depends on the soil pH and environmental conditions. Some deficiencies may be visual, and the growers can identify them after inspecting their crops. The best practice to address such deficiencies is to build a reservoir that could hold and release these nutrients when plants need them. It is also practically possible to supplement micronutrients through foliar spray applications during critical crop growth stages when they need a specific nutrient to complete their particular phases. Generally, soil sampling leads to accessing the exact amount of nutrients available for crop growth. These tests may be conducted before planting a field crop or an orchard. For the yearly nutrient depletion “Leaf Tissue Analysis” determines the number of nutrients to be added to the “Annual Fertilization Program”.
Nitrogen is the most copious element on the surface of the earth and atmosphere, which is needed by plants for growth, and development. On the one end, Nitrogen deficiency is a widespread issue throughout the world. On the other end, it is copious and unsolicited and poses big trouble for humans and the environment. The reason for overuse is simple. The Nitrogen present in the earth’s crust and the atmosphere is not readily available for the intake of plants. Its organic forms exist in the shape of organic matter, plant debris, and bacteria which don’t become instantly available to plants due to the slowrelease N-mineralization process. This process converts mineral N into plants’ available inorganic ammonium and nitrate forms.
Again, the nitrate form is not stable due to water solubility and is often lost from the soil profiles either by leaching or evaporation.
Factors Affecting Nutrients Availability
Multiple factors sometimes hinder nutrient uptake and restrict their availability to the plants. Soil physical and chemical makeup as the soil texture and structure, organic matter content, water permeability, electric conductivity (EC), and pH, largely contribute to accessing the nutrients for plant absorption. Soil water content is among other factors that affect nutrient transportation as the plants only absorb nutrients that dissolve in soil solution. Excess water content also increases carbon dioxide concentration in soil by depleting the soil oxygen essential for nutrient movement. Last but not the least, soil pH is the most critical factor that monitors the overall absorption of nutrients. Besides rich nutrients present and applied to a cropping program, pH determines what to make available for plant growth. Different plant species and crops grow in a range of soil pH, but the acceptable level for most crops remains between 6.5 to 7.5. Sometimes, the nutrient excess leads to chemical toxicity which often stunts crop growth, and a considerable decrease in yield potential and crop health is reported from many growers across the world. The majority of cases claim the excess of nitrogen for declining their production.
Overuse of Nitrogen and Associated Toxicity
A study by (Laila Elhanafi et al) clearly shows that overuse of nitrogen fertilizer could negatively impact total phenolic and flavonoid contents which possess considerable antioxidant properties in sesame seeds. However, biomass and crop yield increased but missing the antioxidant contents in sesame oil which has widely grown across the globe. (1)
China ranks at the top, where the overuse of nitrogen fertilizers in the agriculture crop production system is an issue. The studies conducted by (Shulan Zhang et al) in Guanzhong Plain in Shaanxi Province, northwest China, revealed that the farmers demonstrating over-application of nitrogen in maize/wheat double cropping system were harvesting lesser production than the growers using 30% less nitrogen than the recommended doses for that particular area. Results also revealed the economic benefits of using the least quantity of nitrogen for enhanced crop production. (2)
Some soil microorganisms convert nitrogen into a nitrous oxide which is considered a greenhouse gas. Nitrous oxide that traps in the atmosphere gets heated, resulting in an increase in the atmospheric temperature and triggering global warming.
Nitrous oxide is 300 times warmer than carbon dioxide, a greenhouse gas. Excess nitrogen and phosphorous also cause Eutrophication in waterways that boost algae, fungi, and microorganisms that deplete oxygen from such places. In response, these tiny creatures release harmful gases into the ecosystem, disrupting the aquatic environment.
Since we need nitrogen for our soils that we derive from chemical fertilizers, we need to create harmony between the agricultural production system and environment and adopt ways that prevent nitrogen leakages from the production system besides enhancing crop production.
Nitrogen Cycle in Agricultural Production SystemHave a look at the picture to understand the Nitrogen pathways in an agricultural system which shows how its escape and leakages from the system impact our environment.
Since fertilizers and, especially, nitrogen offer massive production benefits to the agriculture community, their harm to the natural environment is also concerning, as it pollutes water storage, creates an imbalance in the ecosystem, and disrupt biodiversity.
The Source of Unprecedented Nitrogen
The research conducted by Paul West and his associates presents the global estimates of nitrogen application and found that out of the total 115 million tons of applied nitrogen, 75 million tons go wasted. It shows that only one-third of the applied nitrogen becomes part of an agricultural production system, and the rest goes into waste as surface runoff into the atmosphere, water repositories, and the environment. (4)
Some countries undersupply nitrogen in their production system and try to harvest more, which also depletes soil nitrogen and other nutrients that may lose fertility with time.
These countries are called “Negative Nitrogen Miners”. In contrast, some countries supply nitrogen excessively, and their application rates exceed 100 kg per hectare. They’re among the biggest nitrogen-polluting countries, whereas China stands at the top. Moreover, South Korea, Egypt, Taiwan, New Zealand, Singapore, and Kuwait produce 100 kg of nitrogen pollution per hectare. Similarly, the countries in the European Union where overuse of nitrogen is a common practice include Luxembourg, Netherlands, Norway, Slovenia, Ireland, and Cyprus, where each overuses 193.5, 168.0, 126.0, 120.0, 115.0, 103.0 kilograms of nitrogen per hectare, respectively. (5)
Similarly, China is the biggest nitrogen pollutant country which produces almost one-third of the global pollution contributed by the excess use of nitrogen in the agricultural production system as chemical fertilizer. India contributes somewhat one-fifth of the global total, and the US share is 11%.
Comparison of European Countries with the Rest of the World
How to Mobilize Overused Nitrogen for Agriculture Productivity?
- Apply nitrogen as per crop requirement keeping in mind the status of the farm soil. Sandy soils are more prone to leaching, while heavier soil is to surface runoff.
- While preparing an annual fertilizer application program, keep in mind the nitrogen derived from the manure and available from the previous crop residues.
- Apply maximum nitrogen quantities when the crop is ready for intake position, such as middle & late vegetative growth stages.
- Split the entire dose of nitrogen fertilizers into smaller multiple doses and apply through fertigation.
- Your crop rotations must base on one “exhaustive” crop followed by a “restorative” one.
- Mix manure and organic matter soon after spreading it on the soil to avoid soil compaction and reduce surface runoff with timely tillage practices.
Besides all agronomic, cultural, and organic practices, if soil nitrogen mobilization remains a hindrance, adopt a foliar spraying strategy when the crop is actively growing. Such products must contain Calcium, Magnesium besides all micronutrients so that the maximum absorption of nitrogen is made possible through plant roots. It must trigger photosynthesis to make nitrogen use effective. Calcium combined with magnesium, can speed up the absorption of nitrogen by roots and translocate them to the site of interest. One of such well-intentioned products in the marketplace, ” Foliomax”. Foliomax® is chiefly made up of Calcium Carbonate, Silica, Magnesium, and trace elements. Where Calcium Carbonate (CaCO3) varies between 86 – 96%, Silicon Dioxide (SiO2) between 0.10 to 1.7%, Magnesium Oxide (MgO) in the range of 1.25 to 4.5%, Iron between 0.10 to 0.70%, and Manganese (Mn) between the range of 20 to 70 mg per Kilogram with the Carbonic solubility of 65 that helps in stabilizing the soil pH levels. The combination of micronutrients is well suited for foliar applications that show promising results when the crops are under stress and mobilization of the nutrients from the soil is restricted due to the environmental conditions or overuse of nitrogen. Foliomax® is free from contamination and all sorts of pollutants, such as Chlorides and Nitrates, which often spoil the quality of a finished product besides, being harmful to regenerative agriculture. Foliomax® uses Tihomir Lelas’s “Advanced Dynamic Micronization Technology” which produces more reactive mineral particles after colliding them with each other without any chemical reaction being involved. Foliomax® dissolves in water easily, and both Ca and Mg diffuse easily through leaf pores to become part of plants’ nutrition. Application results are quick and improved metabolism is seen within 3-days of applications. Foliomax® is recommended for application in arable farming, pomiculture, Olericulture, viniculture, commercial timberlands, floriculture, and lawns.
- West, P. C., Gerber, J. S., Engstrom, P. M., Mueller, N. D., Brauman, K. A., Carlson, K. M., … & Siebert, S. (2014). Leverage points for improving global food security and the environment. Science, 345(6194), 325-328.