Apple nutrition in Himachal Pradesh
An article in May looked at the Himachal Pradesh apple industry in northern India, and the World Bank project to help increase apple, pear and subtropical productivity. This article looks at nutrient management practices used there.
Plant & Food Research have been engaged for three years to supply experts along with Fruition Horticulture, AgFirst Engineering and Applied Research and Technologies. The team provides training and advice around orchard management practices and plant protection methods.
Historically Red delicious is the main cultivar grown on seedling rootsocks. The industry grows about 40 million cartons with average production of six tonnes per hectare involving more than 100,000 growers, many who are very small scale with only about 50 trees. So giving a value per hectare has little meaning, with rates of fertiliser given as a rate per tree.
There are few flat areas in the state so most plantings are on terraces on steep hillsides. Rows are often curved which makes construction of any support structure difficult. There is now a push to introduce new cultivars on clonal rootstocks and the use of drip irrigation. Virtually all production is marketed domestically.
Looking at this industry gives a good insight to where New Zealand growers have come from in their nutrient management practices. It also highlights the reasons why we do what we do, such as timely trace element applications and foliar sprays, and tracking of soil and foliage nutrient levels. Soil testing has not been a common in most orchards in Himachal Pradesh, but the project has funded and promoted a large increase in the number of blocks tested. In one region where 70 blocks were tested there was a wide variation in soil pH. More than half the blocks tested had a pH that was out of the optimum range of 5.8 to 6.8. With 24 percent of blocks below the optimum pH of 5.8 and a surprising 31 percent of blocks above the optimum pH of 6.8, there were 16 blocks of the 70 above a pH of 7.2.
This gives a huge opportunity for improving their performance. Maintaining correct soil pH ensures that there’s optimum nutrient availability and soil biological activity. Low pH can make some nutrients such as manganese and aluminium highly
soluble leading to toxic levels in the plant and conversely too high a pH can make some nutrients insoluble and become deficient. Highly soluble manganese can result in toxicity symptoms such as ‘bark measles’.
Even in NZ, while there is a good understanding of raising a low pH with lime, growers are less conscious of the potential problems of higher pHs. At a pH of 7, manganese is becoming insoluble and unavailable, along with zinc, copper and iron. At 7.2 it’s virtually insoluble (see Figure 1) resulting in leaf deficiency symptoms of pale interveinal areas. Symptoms are similar to magnesium deficiency except the fine leaf veins tend to remain green.
While leaf testing may show low plant manganese levels, and the response would be to apply a foliar spray with manganese, the underlying cause is high pH, which should be eased back. We occasionally see this problem in NZ and this highlights the fact that the first stage of good nutrient management is maintaining a correct soil pH.
Of course, with nutrients and fertiliser, everyone would like it to be as simple as possible, and Himachal Pradesh, with many small holdings, is no exception. They have developed a system of prescribing fertiliser based on tree age. For an established six-year-old high density planting the recommendation is 210 grams per square metres of urea, 300 gm/m2 of super phosphate and 210 gm/m2 of potassium chloride.
The application area under trees is called the tree basin which tends to be a circular, cultivated area around the tree, often with mounding around the perimeter to contain water, a bit like a miniature border dyke style of irrigation. This equates to very high rates of N P K. For nitrogen this would be in the range 230kg N/ha compared with about 50 - 70kg N/ha applied in NZ. For phosphate approximately 65 kg/ha is recommended compared with 10 - 20 kg/ha applied as maintenance dressings in NZ. The amount of potassium applied is relatively high as well at 250 kg K/ha. These values may be appropriate when building fertility but applied continually are likely to be excess to plant requirements, particularly nitrogen, and detrimental to good fruit set, fruit colour and quality.
Fertiliser is not the only nutrient source. Many of the orchards are part of a mixed farm with animals and other crops supplying a ready source of composted animal manure which is applied, at anything up to 5 kg/m2 as a mulch and slow release nutrient source. While this is very good for soil health, mineralisation of nutrients, particularly nitrogen, is likely to be high late in the season when it’s warm and the monsoon weather is contributing ample soil moisture. This is a period when we would like to see limited availability of nitrogen, to assist with fruit colour development and quality.
Boron deficiency was seen on some orchards. Fruit symptoms are seen early in the season with dark pitting, progressing through to cracks and deformed fruit. This should not be confused with bitter pit, caused by lack of calcium, which is seen late in the season. This deficiency can easily be avoided with foliar boron applications pre-flowering and soil applications.
Also of interest is the widespread use of potassium chloride. We use the sulphate form of potassium, as potassium chloride is considered risky with many horticultural crops due to the risk of chloride toxicity. However, I have yet to see any signs of chloride toxicity even at higher rates used.
As this industry moves to newer cultivars nutrient management will be become even more important. Growers and advisors will gain a better understanding of soil and tissue testing, and plant observation to make better nutrient decisions rather than using a one-size-fits-all approach.