Using Foliar Fertilization to Overcome Crop Setbacks
There are many growing conditions that are beyond a grower's control that can damage crops or inhibit plant growth. Some of the conditions include: excessive rainfall, high winds, hail, insects, herbicide damage, nematodes and compacted soils. Each of these factors can influence the nutritional status of crops. Below are some of the ways that such conditions can influence the nutritional status of a crop. Foliar fertilization offers a way to help a crop overcome or reduce these setbacks and help the crop achieve better yields.
Physical Damage
Loss of Nutrients in Plant Tissues. Some common causes of physical damage to crops are insects, nematodes, hail, wind, and cultivation. Insects eat foliage, stems, roots, and reproductive structures. Nematodes attack the roots. Hail strips leaves off plants and/or punches holes in them. Wind can strip leaves off plants, break stems or stalks, or lay the crop on the ground. When such plant material is lost, photosynthesis, carbohydrate production, and other essential growth processes are reduced. The nutrients that are contained in such tissues are removed as well. These nutrients must be replenished to regrow lost tissues and resume normal growth.
Reduced Nutrient Uptake and Translocation in Crops. Physical damage to roots and plant tissues also reduces nutrient uptake and their movement within the plant. Nematodes or improper cultivation can damage roots, impacting nutrient uptake. Even when heavy winds blow down crops (like corn and wheat) some of the roots systems or vascular tissue inside the stems may also be damaged, thus reducing nutrient uptake and movement inside the plant.
Reduced Nutrient Availability
Active Uptake. There are two types of nutrient uptake by roots. The first one is active uptake, which requires metabolic energy to bring the nutrients through cell walls into the plant. Flooding and extended rainfall can cause the soil to become saturated, reducing the oxygen levels in the root zone, which in turn reduces available oxygen used by roots to convert carbohydrates into energy. This loss of energy lowers the roots ability to take up nutrients.
Passive Uptake. The second method of nutrient uptake is passive uptake. Nutrients are dissolved in the water, and as the plant takes up this water the nutrients are taken up with the water. During periods of high humidity and rainfall, transpiration (the evaporation of water from stomata - natural openings in the leaves) is reduced. When transpiration occurs normally water is pulled up from the roots to replace the water that evaporates from the stomata. But during high humidity transpiration is reduced and so is the quantity of water and dissolved nutrients brought into the plant.
Leaching. Flooding and excessive rainfall can also cause leaching of nutrients from the soil, reducing their concentrations in the soil and availability to a growing crop. Nitrate, sulfate, and molybdate are three nutrient forms that are particularly susceptible to leaching. Leaching is a more severe problem in porous or sandy soils.
Dry Soils. Drought also reduces nutrient uptake. Moisture moves nutrients from the soil particles to plant roots. When soil is excessively dry these nutrients are less likely to come into contact with the roots for either active or passive uptake.
Cold Soils. Another factor is soil temperature. If soil temperatures are much lower (typically in the spring), not only will germination be slowed, but also nutrient uptake by roots will be reduced.
Pesticide and Chemical Damage
Glyphosate and Micronutrient Deficiencies. The mode of action of several widely used agricultural chemicals (such as glyphosate) is to bind to and tie up selected essential plant nutrients. Glyphosate remains one of the most widely used herbicides. It binds most strongly to divalent cations (i.e. those nutrients with a 2+ charge). These include: calcium, magnesium, manganese, iron, copper, nickel, and zinc. When glyphosate is applied to a glyphosate tolerant crop, the herbicide binds to these nutrients inside the crop. Because calcium is part of the plant’s cell walls and magnesium is part of the chlorophyll molecule, glyphosate does not readily bind to these two nutrients. However, glyphosate does readily bind to manganese, iron, copper, nickel, and zinc causing deficiency symptoms known as ”yellow flash.” While yellow flash is most obvious with soybeans it occurs in all crops treated with glyphosate, it is just not as visible. In corn treated with glyphosate the micronutrient deficient yellow leaves are inside the whorl and not readily visible. To prevent this yellow flash, these micronutrients must be applied to glyphosate treated crops to replenish the nutrients tied up by glyphosate. AgriGuardian MicroMix Complete™ was originally developed for this very purpose.
Other Pesticides and Chemical Applications. In addition to glyphosate, other chemicals can cause problems related to plant nutrition. Care must be taken to be aware of the interactions among chemicals, environmental conditions, and stage of plant development. In some cases the combination of the product chemistries may have unexpected results (such as leaf burning, defoliation, flower abortion, and stunted growth), especially under environmental conditions such as high temperatures and humidity at the time of application. For an example, see AgriGuardian™ Grower Journal #7: Micronutrients Help Reduce Herbicide Damage to Crops.
AgriGuardian™ offers a complete line of foliar applied nutrients to address the nutritional needs of all crops, as well as biostimulant products to promote the uptake and utilization of plant nutrients. In addition to AgriGuardian MicroMix Complete™ and AgriGuardian Nutra-Boost®, AgriGuardian™ has foliar applied chelated calcium and all other essential nutrients. When growing conditions limit the nutritional balance of crops, these products can be used to meet the needs of all crops and help to enhance growth, yields, and profitability.
For more information on AgriGuardian MicroMix Complete™, AgriGuardian Nutra-Boost® or other AgriGuardian™ foliar products, please contact your local AgriGuardian™ distributor or visit AgriGuardian.com.
