Physiological disorders and nutritional deficiencies can give rise to quality problems that limit the productivity and shelf life of fruit, thus resulting in financial losses, said Rafael Ruiz Schneider, specialist in plant nutrition, with a Ph.D. from the Polytechnic University of Valencia and graduate in agricultural engineering by the Catholic University of Chile.
The specialist visited Peru, invited by BayerCropcience, to give conferences on plant nutrition applied to grapevines in Piura and Ica, and took the opportunity to visit the table grape plantations of these regions.
He pointed out that the most frequent quality issues Peruvian table grapes face are rachis dehydration and defects caused by physiological disorders related to imbalances in the plant's mineral nutrition, such as Spring Fever or Waterberry.
Spring Fever
Rafael Ruiz said that this disease appears only in the first leaves at the beginning of the season, limiting the foliar development and causing buds to become unproductive. The factors associated with the disease are potassium deficiency, excess of ammonium and early disbuddings.
Soft berry
Regarding this disease, he said that the firmness of the fruit harvested has a strong impact on the quality that the fruit will have when arriving to distant destinations, giving rise to problems such as shattering, decay, browning or necrotic stalk.
Some of the factors associated to the disease include a high load of fruit with low reserves in grapevines (accumulation in certain organs, especially roots of strategic metabolites to supply nutritional deficiencies during certain critical periods. These reserves are: arginines, carbohydrates and phosphorus).
Other factors include excessive vigour and darkening (accumulation of nitrate and ammonia, likely to be toxic), root hypoxia and slow root growth in compacted soils; the root scarcity results in water and nutrients being absorbed at a lower rate, which also generates negative hormonal signals (cytokinins are not produced).
Problems also arise from nitrogen, ammonia or putrescine excess, as well as by a lack of calcium, magnesium, potassium or boron (recent studies have shown its structural role along with calcium in the cell wall).
Waterberry
The plant nutrition specialist also addressed the disease known as Waterberry, pointing out that the symptoms caused by this disorder are: moisture, softening and colour and Brix problems, as well as peduncle and rachis necrosis. "The associated factors are early magnesium deficiency and potassium and calcium deficiency," he explained.
Advice:
In this regard, Ruiz Schneider said that the best nutritional strategy to reduce problems caused by physiological disorders is the use of plants with patterns, as they are more efficient at absorbing nitrogen. On fertile soils, it is recommended to apply only what the fruit absorbs (30-50 T/ha). The use of nitric sources and postharvest urea is also recommended.
It is also possible to combine this with foliar and soil sprays. Foliar sprays with calcium formulated products must be done during: pre-flowering, flowering, settling and 4 mm, 8 mm and 12 mm berry.
Magnesium (Mg) sprays should combine soil (17.4 kg Mg/ha) and foliar applications. Foliar sprays formulated from Mg are recommended on 20 cm sprouts, during settling and with 12 mm berries.
Foliar sprays with boron formulated products should be applied during pre-flowering, flowering, settling and 8 mm and 12 mm berry.
Source: Agraria.pe
