WALNUT
Walnut
The walnut is a big and deciduous tree with a cord in the truck center and with compound leaves formed with odd leaflets. Nuts (walnut fruits) are edible and with a woody shell. Additionally, the walnut wood has a beautiful grain, being very important in the wood industry.

Crop´s requirements
Soil and Water


Physical and chemical charateristics of the soil must assure the best conditions for providing water and nutrients to the trees during the life spand of the orchard. Some of the most important features to be considered are the soil texture and the its chemical composition.

Walnut trees are demanding in relation to soil depth and airation. Root are best developed in medium texture soils without limitations (presence of water table or impermeable layer) up to 1.5 m depth.

Chemical characteristics of soils, such as pH (soil´s acidity or alkalinity index), organic matter content and nutritive elements, as well as the presence of salts and active lime, determine the threes´ behavior. In relation to pH, walnut trees prefer soils with slightly acid to moderate alkaline pH (6.0 to 7.5). The organic matter is fundamental for maintaining a good soil structure and for stimulating roots´ growth. A good organic matter content is considered to be between 2 to 3% in the first 20 cm of the soil.

Walnut trees, without exception, are sensible to low quality irrigation water. Water that contains more than 1.000 ppm of total disolved salts, or more than 300 ppm of chlorides, or more than 0.5 ppm of born, can cause toxicity to the leaves and certain defoliation grade, especially during the summer period when irrigation is abundant.

The lack of water due to a inappropriate irrigation management can affect the growth of the trees, reduce the production and affect the nut quality. Once flowers has been pollinated, there is a rapid growth period of the nuts as a result of an active cellular division. This period takes between 4 to 6 weeks. The lack of water in this phase tends to shorten this perior, negative affecting the nuts´ final size.
For assuring a optimum growth and productivity, trees must maintain an adequate supply of essential nutrients and prevent the accumulation of toxic elements. For obtaining this balance, it is necessary to periodically monitoring the nutrient levels.

In the walnut trees, the foliar analysis is important and it is complemented with a soil analysis for identifiying mineral deficiencies and toxicities. The mineral composition of a leaf reflects several factors, including its age, climatic conditions, availability of mineral elements in the soil, roots´ distribution and actitivity and irrigation mangement. The tree integrates all factors, and the leaf composition reflects this integration.

Desirable concentrations of diferente nutrients has been established for walnut tree species through research and observations.

Nutrients´ concentrations in leaves vary with time, leaf age, position in the foliage and the presence or absence of fruit. Due to this variability, it is essential that sampling techniques must be standardized for valid comparisons.

An adequate Potassium supply on Pecan tree allows to obtain a greater yield since optimizes the photosynthates´ transport toward the fruits. Besides, Potassium participates maintaining the osmotic potential of the plant (cellular turgidity). An implication of this fact is the stomata aperture and closing, which allows the plant to perform water and gas atmospheric exchange. This allows the plant to maintain an adequate moisture status under stress conditions such as salinity, or water availability reduction.

Potassium has an effect on the fruit quality, since it participates on the sugars´ transport from the leaves to the fruits and on the production and accumulation of oils. Crops with a high Potassium content generally show a better water use efficiency, this means, that these consume a relative less water than the crops with lower Potassium content for producing the same biomass. Then, it is possible to conclude that, in the Pecan tree potassium is essential for crop´s growth, development and profitability.
Increased fruit retention and yield with Ultrasol® + Speedfol™

Pecan nuts (Carya illinoensis) are predominantly grown in the USA (280.000 ha) and Mexico (82.000 ha). Other producing countries are South Africa, Australia, Brazil, Israel, Argentina, Egypt and Peru.

Total yield in fruit and nut trees is defined by the number of fruits per tree and the individual fruit weight. Because plant nutrition plays a key role in flower and fruit retention, nutritional imbalances or a high N:K ratio should be avoided as they result in more vegetative growth instead of generative growth, which will reduce potential yield. Augusto Meneses, agronomic engineer and advisor at SQM Mexico, explains why flowers and fruits drop, and clarifies the importance of each plant nutrient in relation to this natural drop phenomenon in pecan nuts.

In pecan, there are 3 natural flower and fruit drops (Fig. 1). The first drop is related to flowers, which are weakened by their low reserves of carbohydrates and nutrients. In addition, all non-pollinated flowers will drop as well. During flowering, boron helps to activate and to accelerate the pollen germination process and consequently pollen tube development. Plants, which received sufficient boron tend to be more successful in setting fruits, which finally results in more harvested fruits. Therefore, a foliar application with Speedfol™ B SP during the pre-flowering stage (2 kg/ha) is recommended.

Figure 1. There are 3 natural flower and fruit drops in pecan trees.
Figure 1. There are 3 natural flower and fruit drops in pecan trees.

B and K for Increased Fruit Retention and Yield in Pecan Trees.

The second drop is related to failures in the fertilisation of the ovule, caused by plant nutritional imbalances and by adverse climatic conditions during the flowering and pollination process. Again, boron appears to play a key role during flowering, as it speeds up the process of setting fruits, when flowers are receptive to pollen. The third drop corresponds to the abortion of the embryo of fruits, weakened by the lack of competitive strength for sugars with other fruits and shoots.

At this stage, the key nutrient is potassium which can be applied with Ultrasol® NKS + Ultrasol® SOP 52 (respectively 100 + 50 kg/ha, 60 days before harvest) or Speedfol™ K SL (1-2 times 4 l/ha, 60 days before harvest). K maintains the proper functioning of the photosynthetic apparatus, which is the carbohydrate factory for nuts. Furthermore, K is the principal carrier inside the plant, and participates in the transport of sugars from the leaf to the fruit.

Pecan trees have a high demand for K, which allows for a fast fruit growth and increased individual fruit weight, thus higher fruit yield. Low availability of K may generate fruit drop (Fig. 2). For reasons discussed before and because of the fact that fruits are no strong competitors for K in the tree, it is recommended to use potassium in the fruit production phase, in particular from the nut filling phase onwards.

Figure 2. Effect of potassium on the percentage of fruit retention per branch in pecan nut. (Bruce W. Wood, USDA – ARS).
 Figure 2. Effect of potassium on the percentage of fruit retention per branch in pecan nut. (Bruce W. Wood, USDA – ARS).
Speedfol™ Pecano SP Cures “Mouse Ear” and Improves the Quality and Quantity of Pecan Nuts.

One of the most important nutritional factors in the production of pecan nuts (Carya illinoensis) in Mexico is the efficient management of zinc, nickel and nitrogen, which the tree needs but which are short in calcareous soils. The pecan tree needs nickel for the efficient conversion of urea to ammonium by the urease enzyme. As a result, when there is insufficient nickel in the plant, the urea is not converted as efficiently, and toxicity may develop.

The most common symptom of a bad urea conversion in the plant is the malformation called “mouse ear” which is characterized by rounded, blunt leaflet tips. Affected leaves and leaflets are often smaller in size than healthy foliage. The rounded leaflet tips result from the build-up of urea to the point of toxicity in the leaf tissue. Other symptoms of “mouse ear” include dwarfing of shoots, poorly developed root systems, rosetting of shoots, delayed bud break, loss of apical dominance, necrosis of leaflet tips, and reduced energy storage by the tree.

Normal pecan tree leaves are elliptic in shape. They are glossy and dark green with paler veins.
Normal pecan tree leaves are elliptic in shape. They are glossy and dark green with paler veins.

Nickel is an important element which, when sufficiently present, permits to maintain good levels and conversion of the nitrogen in the plant. It also avoids “mouse ear” or “little leaf disease” as shown in the pictures above.
Nickel is an important element which, when sufficiently present, permits to maintain good levels and conversion of the nitrogen in the plant. It also avoids “mouse ear” or “little leaf disease” as shown in the pictures above.

In the course of 2010, a trial was set up at the Huerta Fatima, a mature pecan trees orchard of the Western Schley variety, located in Delicias, in the Chihuahua State in Mexico. The goal was to determine the effect of a foliar fertilization with Speedfol™ Pecano SP on the foliar concentration of nickel and nitrogen, and on the quality of the pecan nuts. 1 hectare of crop was designated for each treatment of which more details can be observed in Table 1. In order to evaluate the effect of Speedfol™ Pecano SP, six samples were taken of each plot and nutritional analysis of the leaves was carried out during May, June, July, August, September and October 2010. The evaluation of the nut quality and the number of fruits took place at the moment of harvest.

The application with Speedfol™ Pecano SP had a direct positive effect on the foliar nickel concentration (Figure 1), as well as on the total nitrogen concentration (Figure 2) which is important for the growth, development, yield and quality of the pecan nut.

Figure 1. The effect of Speedfol™ Pecano SP on the foliar nickel concentration, compared to the control (expressed in ppm).
Figure 1. The effect of Speedfol™ Pecano SP on the foliar nickel concentration, compared to the control (expressed in ppm).

Figure 2. The effect of Speedfoltrade; Pecano SP on the total nitrogen concentration, compared to the control (expressed in %).
Figure 2. The effect of Speedfoltrade; Pecano SP on the total nitrogen concentration, compared to the control (expressed in %).

Phenological stage

Month

Treatment

Dose (kg/ha)

2° week after bud break

April

Control

0

Speedfol™ Pecano SP

3

3° week after bud break

April

Control

0

Speedfol™ Pecano SP

3

4° week after bud break

May

Control

0

Speedfol™ Pecano SP

3

Table 1. Overview of the treatments.

The application with Speedfol™ Pecano SP resulted in a significant increase (+ 4%) of the percentage of edible nuts, which is the main quality parameter (Figure 3) and also resulted in a significant increase (+ 8%) of the number of fruits per kg (Figure 4). It goes without saying that both results represent an additional economic advantage for Speedfol™ Pecano SP (Table 2).

Treatment

Price kg % filled (US $)

T/ha

Income / ha (US $)

Speedfol™ Pecano SP

6

1,8

10.800

Control

5,6

1,8

10.080

• The applications with Speedfol™ Pecano SP improve the foliar nickel levels in pecan nut which helps to prevent the nutritional disorder known as “mouse ear”.
• The application of nickel through Speedfol™ Pecano SP had a positive effect on the nutritional status of foliar nitrogen which indicates that there is a synergy between nickel and nitrogen and that the application improves the nitrogen use efficiency in pecan.
• The application of nickel through Speedfol™ Pecano SP had a positive impact on nut quality (fruit fill) as well as on the total number of fruits per kg.

Figure 3. The effect of Speedfol™ Pecano SP on the percentage of edible nuts.
Figure 3. The effect of Speedfol™ Pecano SP on the percentage of edible nuts.

Figure 4. The effect of Speedfol™ Pecano SP on the number of fruits per kg.
Figure 4. The effect of Speedfol™ Pecano SP on the number of fruits per kg.
 

 
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All the information is given to the best of SQM's knowledge and is believed to be accurate. Your conditions of use and application of the suggested products and recommendations are beyond our control. There is no warranty regarding the accuracy of any given data or statements. SQM specifically disclaims any responsibility or liability relating to the use of the suggested products and recommendations and shall under no circumstances whatsoever, be liable for any special, incidental or consequential damages which may arise from such use.