Vigor-Cal: The Natural Calcium Micronutrient

Agro-K Corporation has been eveloping science-based nutrient solutions for a wide range of cropping systems for nearly 40 years. We have developed tools to helps growers produce food efficiently while being sensitive to the environment. Vigor-CalTM is just one of our developments.

Calcium’s Role In Plants

Calcium is one of many important nutritive elements that plants need to grow and remain healthy. Deficiencies in calcium cause many well documented fruit and vegetable disorders such as bitter pit in apples, blossom end rot in tomatoes and soft bottom in melons.

The significant role of calcium in a plant’s inherent ability to resist the establishment and prolif- eration of plant diseases is well documented (Biggs et al., 1997; Marchner, 1988; Palta, 1996).* Calcium’s ability to reduce or prevent infection comes from its ability to increase cuticular thickness and cell turgor. Plants with thicker cuticles and more cell turgor are less susceptible to infection and, if infected, these plants are better able to fight off infection.

Nitrogen And Its Role In Fungal Infection

Nitrogen is a critical element for plant growth. But excessive nitrogen is known to predispose plants to fungal infections. Furthermore, low levels of calcium in plant tissue relative to nitrogen levels have been shown to increase a plant’s susceptibility to fungal infections. Different letters are significantly different at 5% level.


The Balance

Proper nutrient balance is important for a plant to complete its development process. Adequate nitrogen and calcium, in the proper ratio, will lead to increased plant vigor and cuticular thickness – establishing a natural barrier to fungal infections. Growers experiencing an imbalance in
the ratio must increase calcium levels quickly to correct the problem and avoid increasing risk of fungal infections.

Foliar application is the quickest method to increase a plant’s calcium level because it delivers the element directly to the effected areas – plant tissue, leaves, and fruit.

Research Results

The ability for the grape plant to increase its natural disease tolerance is, in part, due to the increase in cell wall thickness and cell turgor. This is confirmed by characterizing berry firmness by measuring the magnitude of deformation caused by a finite pressure. These results are measured in Newtons.

One application of Vigor-CalTM at 2 gal/acre was made to 12 vines of Barlinka table grapes. Six cartons per treatment were packed and stored in cold storage for 4 weeks at 0.5oC and then one week at 10oC. After removal from cold storage, twenty berries were drawn at random from the six cartons (each treatment) and measured for firmness. A significant increase in firmness was recorded.

In another trial conducted by Dr. Uys with Agro-K’s Foliar Calcium significant increases (at 1% level) in berry skin thickness and berry skin cell layers were observed.

The chart at the left shows the impact of the addition of Vigor- CalTM (1 gal/acre) to fenarimol (0.383 oz. a.i./acre). Management of grape powdery mildew, Uncinula necator in Chardonnay winegrapes was significantly enhanced over fenarimol alone. Management of Botrytis cinerea was also enhanced with the addition of Vigor-Cal, but not significantly when compared to fenarimol alone.

The chart above shows the impact of various treatments on the management of Grape Powdery Mildew, Uncinula necator, and on calcium levels in leaves in Chardonnay winegrapes.

The chart above are the evaluations of the same treatments for management of Grape Bunch
Rot, Botrytis cinerea.

Impact of Vigor-CalTM on the Management of Grape Powdery Mildew, Uncinula necator in Chardonnay winegrapes.

Jon Tecklenburg grows Fuji apples in Lodi. In 1997 when Fireblight attacked his apple trees, he sprayed Streptomycin alone in one block and Streptomycin with

Vigor-CalTM in the neighboring block. 1997 was a bad fireblight year. The block sprayed with Streptomycin alone had several strikes per tree which led to losses of entire branches. The block treated with Vigor-CalTM and Streptomycin had only one strike per several trees. This showed Jon that Vigor-CalTM could strengthen cell walls and improve tolerance.

Management By Growers

Cal Rose Nursery in Wasco California, produces nursery stock for cut rose operations. Dave Anderson, Manager of Production, had a Downy Mildew problem in 1997, that exploded in the rose fields and the plants lost all the foliage.

Since he had not had very good results with fungicides in the past when the problem was this bad, Dave decided to tank mix Vigor- CalTM with his standard fungicide and began weekly treatments.

Within two weeks the plants were putting out uniform new growth. Downy Mildew was gone and the plants were strong. He had never seen recovery from such an infection so quickly. He had more canes at harvest translating into better grades and a higher price for the crop.

The first three applications showed no response to the Vigor-CalTM spray. Fourth, fifth and sixth harvests showed a steady decline in infected fruit. The data showed that the invigoration needed “time” to strengthen the strawberry plant. The systemic invigoration needed several sprays of Vigor-CalTM before showing the effects. Vigor-CalTM with Rovral and in sequence with Rovral were significantly better than Rovral applied alone.


Vigor-CalTM, in combination with fungicides used for the management of Powdery Mildew, Bunch Rot, Peach Brown Rot, Lettuce Downy Mildew or Botrytis significantly enhanced the quality and yields of these crops.

Vigor-CalTM alone was very effective in improving the plant’s tolerance to powdery mildew and bunch rot in grapes. There was no reduction in yields where Vigor-CalTM was used alone in comparison to treatments containing fungicides.

The color of the wine produced from grapes treated with Vigor- CalTM alone was clearly lighter in color than that of the wines produced from two (2) treatments containing fungicides. Vigor-CalTM also significantly increased the firmness of grape berries.

Calcium nitrate – This product increases nitrogen levels as well as calcium. However, if the tissue nitrogen/calcium ratio is already out of balance, (i.e., too much nitrogen), then calcium nitrate will do little to prevent or reduce fungal infection and may even exacerbate the problem.

Calcium chloride – This commonly used product contains chlorine which is harsh on plant tissue and may result in phytotoxicity and scarring.