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.

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.

Effect of potassium on the percentage of fruit retention per branch in pecan nut
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.

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).

The effect of Speedfol™ 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 %).

Table 1. Overview of the treatments.

Phenological stage

Month

Treatments

Dose (kg/ha)

2nd week after bud break

April

control

0

Speedfol™ Pecano SP

3

3nd week after bud break

April

control

0

Speedfol™ Pecano SP

3

4nd week after bud break

April

control

0

Speedfol™ Pecano SP

3


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).

Table 2. The extra profit for the farmer when applying Speedfol™ Pecano SP.

Treatments

Price kg% filled (US $)

T/ha

Income/ha (US $)

Speedfol™ Pecano SP

6

1,8

10.800

control

5,6

1,8

10.800


Conclusiones

• 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.

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.

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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