Potato Crop
Calcium
Calcium is perhaps the most important mineral in the soil, significantly influencing numerous chemical, physical and biological processes.
McCains left behind this potato crop as they harvested other crops hit by disease.
When they returned two weeks later, the crop had increased its value by $400/ha.
Balancing calcium levels and correcting any soil deficiencies may, therefore, be the first priority in any fertility restoration program.
Do your cows suffer from milk fever, mastitis, or go down at calving? Does your stock get Barbers Pole Worm? Do you have to combat facial eczema? Are you using bloat oil? Do you have difficulty with calf rearing?
Whatever the disease or problem, there are long-term solutions you can use as part of your calcium-magnesium fertiliser programme that, once corrected, do not have to be repeated year after year.
When the ‘trucker of all minerals’ enters the plant, it takes many other minerals from the soil and helps transport them into the plant.
Among many other benefits, calcium
Plays a significant role in brix building and participates in a number of chemical reactions, e.g. (Mn, K, Mg, B, P, Fe, Zn).
Enhances post-harvest conditions.
Protects cells against toxins and slows the ageing process.
Helps resistance to a range of breakdown conditions such as internal tissue breakdown, cool storage breakdown, lenticel breakdown and bitter pit, because the cell wall is kept intact.
Some deficiency symptoms are
Stunted root systems
Leaves of grasses do not open properly - tips stuck to the lower leaf
Empty peanut shells
Blossom-end rot in tomatoes and capsicums
Cavity spot in carrots
Bitter pit in apples & pears
Black heart in celery
Internal browning in Brussels sprouts
Tip burn in strawberries
premature flower drop and poor seed set
susceptibility to rot disease
These symptoms all relate to poor cell division in the plants growing points, which includes the fruit. A continuous supply of calcium is needed for peak yield and quality.
Calcium is the most dominant cation in the soil and should occupy 60-70% (PAL soil test) of the negatively charged sites of soil particles. The closer the base saturation percentages are to their ideal the harder the magnesium ion will hold onto the colloid.
Note: crops can still perform when calcium is more or less than ideal, but it is the quality and disease resistancethat is compromised, along with soil structure, humus content, soil life, organic matter decay, subsequent nutrient release, and nitrogen-fixing microbes.
Calcium flocculates soil particles while magnesium disperses – so a balance is needed to get good pore space. Pore space provides oxygen and water for plant roots and microbes to thrive in.
A common symptom of the calcium-nitrogen interaction is seen in leaf tests where nitrogen levels are excessive and calcium is deficient. It is the nitrate ion that combines with calcium to form calcium nitrate which is then leached away in the soil.
Calcium is very immobile in the plant hence deficiencies are found mainly in the younger leaves; a main constituent of cell walls which play a role in resisting insect and fungal attack. Calcium is necessary for growing points of leaves and roots, and stimulates seed germination. It does not transport from one part of a plant to another, so newly formed roots, stems and leaves need a continuous supply from the soil.
Calcium sources
Golden Bay Dolomite with, 24% Ca and 11.5% Mg, is the best material to improve soils where both magnesium and calcium are required. To ensure the soil calcium-magnesium quantum remains balanced, a mix of dolomite and lime may be necessary. The finer lime is ground, the better, although the faster it will be used up. Gypsum (23% Ca, 18% S) is also a good materrial to use in certain circumstances. Often Gypsum is oftem over-applied and wrecks havoc with magnesium and other cations. It is ususlly applied in large amounts, so remember that sulphur can strip out cations. If calcium is deficient, in some circumstances, calcium will decline with the application of Gypsum. Hydrated lime, calcium hydroxide or burnt lime, or calcium oxide are some other forms.
For every one percent you increase calcium, magnesium is reduced by one percent (provided it is not badly deficient).
