What are fertilizers?
A fertilizer is any material containing nutrients in known amount which can be applied to the soil and leaves. The main purpose of the fertilizer use is to get higher yields. Soil analysis helps in determining the nutrients needed by apple fruit trees.
Fertilizing apple trees
Apple trees require fertilizers to live and grow. The nutrients are very important because if one or more of the nutrients are deficient in the soil, the tree will not perform well and will be more susceptible to diseases and will have shorter life span than a well fertilized tree. The apple trees require total thirteen nutrients some in larger quantity and some in lesser quantities. These apple nutrients can be classified in two major categories:
- MACRO NUTRIENTS
MACRO NUTRIENTS are required by apple trees in larger quantities. The macro nutrients required are Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg) and Sulfur (S).
MICRONUTRIENTS are required by apple trees in smaller quantities. Their deficiency can be covered by foliar applications. The micronutrients include Boron (B), Zinc (Zn), Manganese (Mn), Copper (Cu), Iron (Fe), Chlorine (Cl) and Molybdenum (Mo).
Labeling of Fertilizers
Labeling of fertilizers helps in determining the amount of nutrients present in the fertilizers. Normally labeling is done to show the amount of nitrogen, phosphorus and potassium (N:P:K). The value of nitrogen represent amount of element Nitrogen, P represent amount of Phosphorus pent oxide (P2O5 ) and K represents amount of Potassium Oxide (K2O). For example a fertilizer labeled N:P:K 12:32:16 represents 12% Nitrogen, 32% P2O5 and 16% K2O.
Labeled fertilizer represent nutrients amount of N, P2O5 and K2O. So to know exact element amount of N, P and K following conversion is needed.
- Nitrogen represents actual amount so there is no need of conversion.
- P2O5 contains 56.4% oxygen and 43.6% phosphorus. For example if 1000 grams of 12:32:16 is applied, plant get 32% P2O5 which is equal to 320 grams. But it is a mixture of oxygen and phosphorus and it contains 43.6% phosphorus which represents 139.52 grams of elemental phosphorus. (43.6% of 320 grams)
- K2O contains 17% oxygen and 83 % potassium. For example if 1000 grams of 12:32:16 is applied, plant get 16% K2O which is equal to 160 grams. But it is also a mixture of oxygen and potassium and it contains 83% potassium which represents 132.80 grams of elemental potassium. (83% of 160 grams)
When and how much to Fertilize?
Apple trees experience growth during spring followed by slower growth in summers. So the nutrients should be available to the tree when this growth is going to start. The best time to apply fertilizer is from early spring to late spring. Trees can come under stress after harvest, so post harvest application of fertilizers is also needed. It is essential that soil should have moisture while applying fertilizers. Fertilizers should be avoided in warm and dry summers. The amount of fertilizers to be applied should be determined by soil analysis and leaf tissue analysis. Last year growth also suggests the amount of fertilizers to be applied, if last year growth in bearing trees was less than 10 inches then there is surely deficiency of nitrogen. Adjust the amount of fertilizers according to the crop load; heavy crop will definitely require more amount of fertilizers. An average standard apple tree require (700:350:700)gms of N:P:K annually.
How to apply Fertilizers?
The first and easiest way to fertilize is to spread the fertilizer on the ground. Fertilizers should not be applied near to the trunk as it can injure the roots. After applying fertilizers they should be thoroughly mixed with soil. If soil is dry, water the ground as soon as possible.
Secondly, fertilizers can be applied by foliar application especially in case of micronutrients. Water soluble and foliar fertilizers can be applied by spraying them on the trees. It helps in quick uptake of the nutrients.
Thirdly, the fertilizers can be applied through fertigation. It is a method of fertilizer application in which fertilizer is mixed with irrigation water by the drip system. This is highly efficient method because the availability of nutrients is very high.