A good fertilisation scheme is important to reduce the plant’s susceptibility to pests and diseases.
The effects are largely due to cationic nutrients – most notably potassium and calcium – improving tree and nut integrity and strength.
Potassium maintains good growth and strong nut fill, while calcium has a direct effect on strengthening cell walls and maintaining cell membrane integrity, helping prevent cell breakdown and disease ingress.
Calcium can also help trees resist fungal or bacterial infection by suppressing the extra-cellular enzymes these pathogens secrete.
In trials comparing, N, P and K rates, high rates of fertilizer use reduced susceptibility to Botryosphaeria dothidea (panicle and shoot blight) in pistachios. The most effective nutrient at maintaining low levels of this disease, even at low rates of use, was potassium.
Better K-supply and higher leaf tissue levels also curtailed the incidence of verticillium wilt in pistachios, maintaining higher yields.
Calcium – supplied as calcium nitrate - improves nut quality as well. In a series of trials on hazelnuts, YaraLivaTropicote increased yields, but the key added benefit, calcium response, was reduced levels of mould and internal brown cavity postharvest.
In a similar fashion to potassium, calcium use has also been shown to reduce the incidence of panicle and shoot blight - Botryosphaeria dothidea.