Bumper yield from balanced fertilization
Bumper yield from balanced fertilization
Healthy soil for healthy vegetables
Rice research goes site specific
Grown in practically every country of the world, potatoes are now enjoying unprecedented success in India. From 4.5 Mt in the seventies to almost 20 Mt in 1996, India has now become the fifth largest potato producer in the world. As Figure 2 also shows, potato yields are still fairly low, achieving just over the global mean of 16.1 t/ha. Trials supported by IPI demonstrate that if potato quality is to improve in line with the demands of growers, consumers and the processing industry, potash must not be neglected.
| Figure 2: Potato production and yield of the 5 major producers |
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| mean 1995-97, FAO |
| Potato production million t |
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| potato yield t/ha |
Potatoes are a high value cash crop grown in the north of the country between November and March. The season for the fresh vegetable is short because as soon as the soil temperature rises, tuber growth stops. Growers are then faced with the major problem of lack of cold store facilities. Their only option is to sell the crop which means that markets overflow at harvest time and prices plummet. If growers could keep their potatoes, even for a few weeks, the price they could obtain would increase well beyond the level required to cover the inevitable losses that would occur in store. Anything that could be done to increase shelf life, or suitability for processing, would be of great benefit to farmers, processors and consumers. Potash is the nutrient that is critical for quality.
IPI has supported an extensive programme of field trials to investigate the effect of balanced nutrition with potash on yield and quality. P. Imas and H. Magen (IPI Coordinator, India) report that tuber yields in West Bengal could be increased to almost 30 t/ha with application of 100 kg/ha of K2O, compared to the NP control of 12 t/ha. Growers’ net income could be boosted by an additional Rs 15,000 per hectare with such a yield. In Shimla, Himachal Pradesh, moderate levels of N, combined with 150 kg/ha of K2O, increased yields by 5 t/ha and net income by more than Rs 4,000/ha. Tuber growth, and therefore yield, are reflected in the status of leaves. Plants that are grown in K-deficient soils show early senescence of the shoots, bronzing and scorching of the leaves and increased risk of late blight (see Figs. 3-9). Without balanced fertilization, there will be no bumper yield.
A major development in recent years has been the growth of the potato processing industry. Again, potash has an impact on processing quality because sufficient K allows the plant to convert sugars to starch efficiently. Without sufficient K, the sugars remain and chips made from such potatoes are darker and more bitter in taste after processing. In Uttar Pradesh, work by Bansal and Shahid Umar* (1998) demonstrated that not only does chip colour improve when is applied at 225 kg/ha but that yields increased by up to 45% and dry matter content increased from 16.7% to 22.1%. All these factors please the processors as well as the growers. Sufficient K during growth also improves the shelf life of fresh tubers. The value/cost ratio increased by 30% when tubers could be kept two weeks longer in store and by 60-70% at four weeks. Each rupee invested in as SOP returned five rupees with higher yields when sold at harvest but around seven rupees after two weeks and more than eight ru pees when sold after four weeks. These prices relate to 1996-97 but, with the relatively high potato prices in 1997-98, the value: cost ratio improved still further.
IPI will present its activities and results at the forthcoming "Global Conference on Potato", New Delhi, India, 7-10 December 1999.
* Bansal, S.K. and Shahid Umar (1998): Effect of SOP on yield and quality of potato. Fertilizer News, pp. 43-46, November 1998.