When the monsoon rains fail – Potash secures crop yields and preserves soil fertility under adverse growing conditions
In the tropical and subtropical climate regions of India, yield strongly depends on monsoon rainfall. If the rains fail or come down at an inappropriate time of the year, a serious drop in crop production can be expected. Adverse climatic conditions are accompanied by serious nutrient deficiencies of soil. First of all potassium (K) is lacking at many sites in India.
Among nutrients, potassium has the most beneficial effects on drought resistance of crops. K regulates the water budget of plants and prevents them from drying-out. Thus crop performance will be kept on a high level even under unfavourable growing conditions.
Potash saves water
However, under water shortage in India, the poor ratio of potassium (K) and phosphorus (P) to nitrogen (N) application can aggravate the situation. The high dosage of N in comparison to K and P does not meet the physiological requirements of the plant. N stimulates crop growth only when there is sufficient soil humidity. Therefore a sole N application under drought conditions will be more or less ineffective. Numerous field trials worldwide have shown the beneficial effect of a balanced NPK application. The higher the K supply, the lower is the yield reduction caused by drought periods. K applied to spring barley during a very dry season resulted in an extra yield of + 80 %, whereas in a “normal” year the increase in yield was much lower (+ 25 %).
Recent studies have shown the beneficial effect of K on the water holding capacity. K supply in a field trial improved water holding capacity by 14%, representing a surplus of 30 mm rainfall. Thus soil fertility will be significantly improved by K application even under drought conditions. Thus the old saying “potash saves water” is still true. Sufficient K application can protect Indian farmers from yield losses due to low monsoon rain.
Under conditions of soil salinity and for chloride-sensitive crops Sulfate of Potash (SOP) is the preferred K fertilizer
Drought and reduced soil humidity are often accompanied by high salt levels in the soil solution. As a consequence plants can not absorb enough water and consequently yield drops. These conditions require the use of SOP. It is virtually free of chloride and does not contribute to salinization of soils. This is of particular importance for chloride-sensitive crops such as fruit trees and tobacco. In addition to K SOP provides the essential nutrient sulphur (S) in its most plant available form.
Effects on crop quality
It has been shown in Indian field experiments, that the quality of high value crops such as fruits, vegetables or tea was improved after SOP application. Fruit quality parameters such as colour, sugar content and taste will be improved as well as storage suitability. In India, SOP experiments have been conducted with tea, mango, banana, pineapple, pomegranate, chilli, onion, potato and tomato in cooperation between IPL and K+S KALI GmbH.
When the monsoon rains fail India – due to the K content of its soil – will be threatened twice: A lack of water and K in the soil. To improve the soil K content by greater K inputs can be a deciding measure to secure soil fertility and crop yield during periods of water shortage. The present K fertilizer input is far below the physiological requirement of most field crops. Under saline conditions and particularly for cash crops the use of SOP ensure high yields and optimal crop quality.
Dr. Georg Ebert
Agronomist of the K+S KALI GmbH Agricultural Advisory Department in Kassel, Germany