The value of organic matter in kiwifruit cultivation

From this perspective, organic matter becomes a key agronomic factor: it improves soil structure, supports microbial biomass, increases cation exchange capacity and makes nutrient availability more stable over time. Organic fertilizers and organo-mineral fertilizers, when selected on the basis of their composition and the quality of the organic matrix they contain, as well as applied at the right time, increase overall soil fertility without causing imbalances between vegetative growth and crop production.

The relative stability of the total cultivated area contrasts with significant fluctuations in yields: potential production is often higher than the quantity actually harvested due to the high frequency of unfavourable seasons caused by climatic factors (frost, high temperatures, water shortages) and biotic factors (kiwifruit vine decline and other adverse conditions).

Production is concentrated in a few specialised growing areas. Lazio, particularly the Agro Pontino area, accounts for approximately one third of the volumes produced, followed by Piedmont, Emilia-Romagna, Veneto and Calabria.

In Italy, green-fleshed varieties of Actinidia deliciosa are still the most widespread, although cultivation of yellow- and red-fleshed selections of Actinidia chinensis is increasing. This change is not merely commercial: vigour, harvest period, chilling requirements, nutritional requirements and dry matter accumulation capacity vary among genotypes. Consequently, fertilization strategies must also be tailored to individual varieties rather than standardised.

Prevention requires drainage, raised beds where necessary, sensor-controlled irrigation, limiting machinery traffic on wet soil and the use of healthy nursery material. Adequate soil organic matter levels can make the root system more resilient by promoting soil aggregation, balanced water infiltration and biodiversity.

Beneficial microorganisms should also be included in kiwifruit vine decline management strategies: mycorrhizae, Trichoderma, Bacillus and selected rhizosphere microbial consortia can stimulate root development, promote nutrient uptake and compete with pathogenic fungi.

During pre-budbreak (vegetative growth resumption), particular attention should be paid to Nitrogen application, supplying only a fraction of the annual requirement. At this stage, Nitrogen is mainly required to stimulate canopy development. Adequate Phosphorus availability is also important in spring to stimulate root activity. Iron availability should also be monitored during the period of most intense vegetative development, especially in soils with a higher pH, to prevent iron chlorosis.

During flowering and fruit set, Boron availability is important for reproductive processes. However, care should be taken because excessive levels of this element can cause phytotoxicity in sensitive cultivars.

During fruit growth, Potassium plays a key role, supporting sugar translocation and fruit size. However, excessive rates can disrupt the balance with Calcium and Magnesium, which are important respectively for improving fruit firmness and storage potential, and for supporting photosynthesis.

In the weeks preceding harvest, it is advisable to limit Nitrogen applications if vigour is already high, in order not to negatively affect dry matter accumulation, fruit firmness and storage potential. Post-harvest, as long as the leaves remain photosynthetically active, moderate nutrition can promote the accumulation of reserves. However, this application must be evaluated according to the length of the growing season, the condition of the leaf canopy and the risk of leaching. Post-harvest applications must not stimulate late vegetative growth that would be susceptible to cold damage. Organic fertilizers inoculated with beneficial microorganisms can also be applied at this stage. These can help restore balance in tired soils and/or soils depleted by the recently completed growing season.

When appropriately selected according to their content of macro-, meso- and micronutrients, organic and organo-mineral fertilizers can meet crop nutritional requirements while ensuring an optimal match between nutrient availability and peak plant uptake, while at the same time reducing inefficiencies and the amount of nutrients lost through leaching, volatilisation and immobilisation.

But there is more: the organic matrices contained in these fertilizers, provided they are of high quality, meaning highly humified and derived from controlled sources, have a positive impact on the physical and microbiological properties of soils. This is particularly important for kiwifruit given some of its specific characteristics: the need for a constant water supply, sensitivity to waterlogging and the rapid spread of kiwifruit vine decline, which is closely linked to soil imbalance and degradation.

Lastly, organic and organo-mineral fertilization is of primary importance in organic kiwifruit cultivation, as the number of permitted mineral fertilizers is extremely limited and restricted to those of natural origin.

When present in adequate quantities in the soil and in its different forms (from the most labile to the most stable), in balance with one another, organic matter mitigates fluctuations in water availability, supports plant nutrition, limits the effects of compaction, contributes to resilience against heat and drought, and helps counter complex plant health problems such as kiwifruit vine decline, also by stimulating the proliferation of beneficial microorganisms and the biodiversity of the soil microbiota.

Biocomplex 6.8.12 is produced from a blend of organic fertilizers with a high Nitrogen and Phosphorus content, with the addition of Potassium sulphate, providing a complete organo-mineral fertilizer containing all the nutrients required by plants and an ideal ratio between the different nutrients. Biocomplex 6.8.12 provides a rapid yet prolonged fertilizing action, with the gradual release of all the organic Nitrogen it contains, enabling a single application at the beginning of the crop cycle. It also promotes intense microbial activity in the soil. The presence of free amino acids provides a biostimulant effect in synergy with humic acids, enabling a rapid resumption of root activity even under adverse conditions, such as heat stress. Biocomplex 6.8.12 is permitted for use in organic farming.

Agri Bio Aktiv is a soil activator based on humified organic matter and bacterial and fungal inoculants. In addition to providing organic matter and nutrients, it promotes and directs the proliferation of microorganisms in the soil that are beneficial to plant development. When used post-harvest on kiwifruit, it promotes the accumulation of reserves in the plant during autumn, helping it to better withstand the resumption of vegetative growth the following spring. It also revitalises tired soils or soils depleted by intensive crop production and, thanks to the presence of Trichoderma and rhizosphere bacteria, helps counter pathogenic fungi such as Fusarium, Pythium and Phytophthora through antagonistic activity.