John Kempf

Nutrition helps cut fruit stay fresh longer

We expect a cut apple to turn brown within a few hours if left exposed to the air.

Some people have noticed that occasionally apples turn brown only very slowly, taking a day or longer.

The change from white flesh to brown is result of polyphenol oxidation.

Common advice for people who want to avoid browning while cooking with apples at home is to coat them with lemon or pineapple juice. Both of these juices provide antioxidants, which slows or stop the oxidation process, and prevent the polyphenol breakdown.

This begs the obvious question, what if the apple contained high levels of antioxidants to begin with?

When plants have nutritional integrity, they will produce much higher concentrations of antioxidants, which might be part of the explanation why some apples do not turn brown quickly.

This half eaten apple (grown with good nutritional balance) was deliberately left to see how quickly the polyphenols would oxidize. This photo was taken 96 hours after it was left on the counter.

Apples browning quickly is a nutritional imbalance problem, not a genetics problem that we should try to solve with genetic engineering.

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John Kempf2021-02-02T20:47:55-05:00February 3rd, 2021|Tags: apples, quality, storage|

Managing shoot growth, terminal buds, and biennial bearing

For many perennial fruit crops, we can use shoot growth as an indicator of overall plant energy and vigor. It is common for shoot growth to slow down, and sometimes even stop completely, setting a terminal bud, during the fruit fill period.

When this occurs, it is an indicator that the plant is not producing enough photosynthetic energy to both fill fruit and develop growth, so it will sacrifice the new growth to be able to reproduce.

When we manage plant nutrition to optimize photosynthesis, it is possible to restart healthy new shoot growth, without the addition of nitrogen.

On these apple trees in Michigan, the trees set terminal buds on new growth tips in late June, during early fruit fill. We started working with this block this year and recommended foliar nutrient applications designed to increase photosynthesis to increase sugar production for the heavy fruit load.

Incredibly, the shoots that had set ‘terminal’ buds began regrowing! Perhaps terminal buds aren’t so terminal after all when supported with enough energy and the needed nutrition. These shoots continued to have healthy growth with tightly spaced nodes through the fruit fill period.

When trees have continuous healthy shoot growth with tightly spaced nodes, it is indicator they have enough energy to also set fruit buds for the following year, and we can effectively prevent biennial bearing.

John Kempf2020-10-01T06:02:58-05:00October 1st, 2020|Tags: apples, biennial bearing, terminal buds|

Nutrition management for apple scab

Some apple varieties are quite susceptible to apple scab, while others are resistant.

Plant sap analysis indicates the resistant varieties are much better at absorbing cobalt than the susceptible varieties in the same soil conditions. They will often show 2-3x higher cobalt levels.

When we balance all the other nutrients and apply foliar applications of cobalt to susceptible varieties, apple scab is not present. We have implemented this treatment successfully on enough different apple varieties on enough different orchard blocks to be confident of its success.

Many other diseases have similar correlations to nutritional imbalances and can be managed effectively by managing nutrition.

Preventing and reversing scab infections can occur very quickly. We expect to see reduced pressure within weeks of the first application. In several cases, we have been able to eliminate all the later scab treatments after cobalt was applied in the spring, within several weeks of beginning to work with a block for the first time. This reduced the pesticide budget requirements by $500.00-$600.00 in the first year.

Like any trace mineral, cobalt can easily be overdone. Don’t attempt treatments without using sap analysis to evaluate progress and nutritional balance.

Not all diseases respond this quickly to nutrition management, but many do. When we begin managing nutrition differently, we can dramatically reduce fungicide and insecticide applications on most crops.

These Gala apples had severe scab pressure in a mild scab year in the year before treatment. In the current year, they had no scab, in spite of heavy scab pressure.

John Kempf2020-09-25T06:52:03-05:00September 25th, 2020|Tags: apple scab, apples, cobalt|

Bark splitting on trunk and branches caused by calcium deficiency

The split bark you see here is an extreme example of one calcium deficiency symptom in fruit and nut trees. When trees have adequate levels of calcium the bark can expand rapidly and does not split, maintaining a smooth appearance until they are decades old.

When the bark becomes so tight that it eventually splits from pressure, the flow of water and nutrients to the canopy and the fruit is also limited, which results in reduced quality and nutrient movement into the fruit.

The solution is to make sure that our soils have adequate calcium levels, and a proper balance with other cations. It is important to note that these are two different things. The threshold for disease resistant crop production is at least 1000 ppm calcium in the soil as measured by Mehlich 3 or ammonium acetate extraction. On sandy soils with low cation exchange capacity, soil reports can indicate that the calcium supply is balanced with other cations, and no more needs to be added, even when the soil only contains 400-500 ppm. In this type of scenario, more calcium definitely needs to be added to maintain crop health and performance.

John Kempf2020-06-25T08:26:12-05:00July 6th, 2020|Tags: apples, calcium, calcium deficiency|