Fertilization in Walnut Cultivation

In recent years, a large-scale walnut garden has been established in every region of our country. Walnut trees which are have a longer life than other fruit trees, the following points should be considered before establishing a walnut garden.
Late spring frost and early autumn frost condition should be considered.
During the Fructification period,  the temparature over +40 C0 and excessive sunshine may cause blight (browning) in the green shell of the fruit and crust color of the fruit can be darkened.


It should also be taken into account that extreme colds (-20 C0) are present in the rest period after pouring the leaves.

These issues should be determined in consultation with a specialist before determinig the type of the walnut.
The soil requirements of walnut trees
Due to its long-lasting and very large tree structure,  the pile roots of a walnut tree can go down to a depth of 2.5-3 m. It likes alluvial and deep-built soils with its lightweight, loamy soil, sandy loam and loam structure. Ground water should not be high. Water holding capacity of soil should be good because it is a plant that loves water and rain. It should be rich in organic matter, less calcareous and the Ph value of the soil should be slightly acid and neutral (6.0 - 7.5). In the walnut orchards found in very calcareous and high Ph value (more than 8) soils, the young leaves of the trees usually have iron and zinc deficiency.
 Fertilization at walnut garden
Before the plantation of walnut samples, walnut gardens based on the size of the land and type of the soil, the soil samples taken from different depths and also at a depth of 1,5 m should be analyzed.  The reason of this is to determine the soil properties of the substrates that make us to determine which fertilizer will be used when it comes to full yield age and also plant fertilization. Plant fertilization is the fertilization of the entire area or planting pits before planting.
According to the results of soil analysis, if the soil Ph value is above 8, it is important to lower the soil Ph value to 7.5 or slightly lower (7.0) by applying elemental powdered sulfur to the whole area before opening the seedlings pits. This is important for the usefulness of nutrients in soil.
The powdered sulfur that will applied to the soil, if mixed with well-burned animal manure (except for animal feed and chicken manure and goat manure), the effect is seen in a better and shorter time. The appropriate sulfur soil should be mixed to the depth of 20- 30 cm at the same day if possible. If this is not done, a table spoon should be applied to the planting pits of the seedlings.
After the aplication of Sulfur, the hydrogen (H) + ion that occurs due to the enzymatic reaction of sulfur bacteria in the soil, decreases the soil Ph value (the hydrogen ion is not absorved from the soil by the plant). Sulfate (SO4) occurring in the soil is the form of sulfur from the soil as a plant food. Some amount of the sulfate is absorved by the plant, while some of it has a electric charge and is washed away deep into the soil.
The amount of elemental sulfur to be applied to the soil depends on the structure of the soil (light to medium to heavy) and the depth of the soil that the Ph level will be reduced. For deep-rooted walnut trees, reducing the PH value of the soil by one unit (for example, decreasing the pH of 8.5 to 7.5), for permeable soil (loamy timber-sandy loam) soils, 70-80 kg per hectare, for medium permeable soils, it is necessary to apply 90- 100 kg per hectare.
Sulfur application can be repeated 8 to 10 years after planting, depending on the quality of irrigation water.
Soils are generally poor in potassium, magnesium and phosphorus. Walnut trees grow well in permeable alluvial soils. According to the results of the soil analysis, fertilizers containing phosphorus and potassium do not penetrate too deeply with precipitation and irrigation water and they are not sufficient in soil. In order to meet this need and balance the nutrients in the soil until the seedlings begun to give fruits (3-7 years depending on the varieties), plant fertilization is done in the amounts specified in Table 9 before plantation. Since the soil of our country is generally deficient in zinc, zinc fertilizer should be used in plant fertilization. If this is not possible, the fertilizer shoud be pour down in the pits. The amount of fertilizer to be given to a decare in the plant fertilization is given in Table 9.
 
Plant fertilization may not be performed in the whole area of the walnut garden planted at wide intervals. In this case; in the bottom of the planting pits that opened as 60x60 cm depth and width; 125 - 150 gr of Triple Super Phosphate or DAP (Diammonium Phosphate), the same amount of Potassium Sulfate, 50-60 gr of Magnesium Sulfate and a teaspoon of ( 2 .3 gr) zinc sulfate should be poured down and after that the plantation must be done.
Green Fertilization
Walnut plant land is generally poor in organic matter. Increasing the organic matters in the soil by using animal manure is both expensive and also fresh animal manure may cause the soil weeds and some soil diseases and pests are transmitted. Instead, If intermediate agriculture (short-term vegetables, etc.) will not be done between the walnut trees; the green fertilizer plant such as vetch-sainfoin may be planted (from the beginning of autumn to spring). The fertilizer plants that are in the middle of the flowering period shoud be mixed by soil by plowing. This process is called as green fertilization.
Since the root systems of green fertilizer plants bring the nutrients in the depths of the soil to the stem and leaves, When the soil is mixed, the upper layers of the soil are also enriched by the nutrients. The soil is also will be enriched with nitrogen because, the green manure plants benefit from the nitrogen of the air. In addition, as a result of the degradation of the green fertilizers by soil microorganisms, the soil is enriched with organic matter and humus (humic and fuvic acid). By planting green fertilizer plants, there will be no wild weed extraction, it means that there may be no need for wild weed control. Because of the green fertilizing,  there will be no need of appliying animal manure to the soil each year.
Sapling Fertilization
According to walnut varieties, walnut seedlings are 3 or 7 years of age when they began to yield. During this period, to make the seedlings to have a strong root structure and the above ground to ensure healthy development of fertilization is required. Both the sapling age and the full yield-age walnuts are generally fertilized in two separate periods. The first fertilization is done 2-3 weeks before the begining of the spring that saplings begin to give shoots. This fertilization is called base and sub-soil fertilization. Fertilizers given in the form of broadband (60-70 cm), if drip irrigation system is in use fertilizer should be given between the irrigation pipes.  Then fertilizers shoud be mixed into the depth that will not cut the roots if . 
If we use irrigation pits instead of drip irrigation the fertilizers should be given side of the irrigation pits (away from the main body). In the soil fertilization, according to the result of soil analysis, all of phosphorus and potassium but half of nitrogen that needed is given. The remaining part of the nitrogen is applied at 1 or 2 times before the watering (after flowering period and during the fruit growing period) and than the saplings sould be irrigated. In drip irrigation, 60-70% of phosphorus fertilizer, 50% of potassium fertilizers and 30% of nitrogen fertilizer are applied during the soil fertilizing period.
The remaining part of the fertilizer is applied to each irrigation system in accordance with the irrigation program with fertilizers suitable for the drip irrigation system. Table 2 shows the amount of fertilizer to be given according to the age of the seedlings in the pit irrigation process. As the walnut trees are sensitive to salinity, the fertizer including chlorine (CL) should not be used. Instead, potassium sulfate fertilizers should be used.
If there is soil analysis, the fertilizer should be used according to soil analysis.
 
The fertilization program in walnut seedlings with drip irrigation system is given in Table 11.
If soil analysis is available, use fertilizer according to soil analysis.
Base Fertilization: 10 kg of potassium sulfate fertilizer per decare is divided by the number of trees in the decare and given to the part of the drip pipes and mixed into the soil. The amount of fertilizer given for one year is increased by 15% every year until the seedlings full yield.
 
 Note: The monthly amount of fertilizer is divided by the number of irrigation to be carried out in that month. Fertilizer quantity is increased by 15% every year until the seedlings full yield.
If the rain starts do not use the fertilizer given for the month because the irrigation will not take place. 
Fertilization of walnut trees in full yield
Base and upper fertilization times and shapes are made as given in the saplings fertilizing section. Fertilizer should be used according to irrigation method. Mix the base fertilizers to the depth that will not harm the roots and away from the body of the tree according to the light, medium and heavy structure of the soil. Match upper fertilization before precipitation. Use fertilizer according to soil analysis and the amount of crops that might be harvested per tree. Do not use potassium fertilizer or composite one that includes chlorine since walnut trees do not like salinity. For the increase of fat, protein and aroma in the kernel of the walnut, choose potassium sulphate base fertilizers.
Table-12 Fertilization walnut trees in full yield:
Nitrogen; is the main nutrient for the growth of seedlings and trees.
Phosphorus; strengthens the root growth of the tree. Increases the number of flowers and fruits. It increases the quality of the walnut and ensures that the harvest is done within the expected time. In low-pH soils where lime application will be applied, phosphorus fertilizer should not be used with lime. Phosphorous fertilizer application should be made at least one month after lime application.
Potassium; provides large and fuller kernel formation. It prevents hollow walnut formation. It is directly effective on quality.