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Case Study Foliar Application of Fertiliser.

A case study demonstrating that foliar application of fertiliser is an ideal method for boosting plant growth, correcting nutrient deficiencies and improving crop returns.

Foliar application of fertiliser is a method of supplying plant nutrients directly to plants by spraying water-dissolved fertilisers directly onto leaves to support the growth and production of plants. It is a complementary method of fertiliser application and is not considered as a complete substitution for supplying essential nutrients required by the crop through soil application of fertilisers. The applied nutrients are readily absorbed by leaves. If moisture of the applied fertiliser is lost, nutrient uptake is temporarily discontinued. However, at night, the dew re-dissolves the fertiliser and uptake of nutrient is renewed. The mechanism of foliar uptake of nutrients involves its penetration (mainly passive diffusion) through cuticle or stomata and translocation of the absorbed ions through vascular channels (phloem, xylem) from the leaves to the active plant system.

Plants need nutrients at different rates and at different stages of their growth. The rate and period of uptake as well as utilisation of nutrients may vary in different types of plants. Therefore, plant nutrients need to be supplied at the rate and time that match with their nutritional needs to optimise nutrient use and yield. To understand the nutrient requirement, soil and plant tissue analysis is essential. These nutrient assessment techniques will help us to consider a priority based action for supplying the crop limiting or deficient nutrients through appropriate methods.

For optimal crop productivity, nutrient deficiencies should be avoided. If the same crop is grown continuously for several years, mineral deficiencies would likely occur if they are not supplied adequately or if such minerals are mostly deficient in the soil. The growth and development of nutrient deficient perennial crops are more vulnerable to disease and pest attack, weed pressure and environmental stress conditions. If nutrient deficiencies are diagnosed in plant tissues, an immediate action for supplying these nutrients is required urgently for correcting deficiencies, strengthening plants to compete with weeds for light water and nutrients, recovering from environmental stress and optimising crop growth and yield. This rapid action for supplying crop nutrients is possible through foliar application of highly soluble plant nutrients.

When is foliar nutrition required?

Under adverse soil conditions, foliar application of nutrients is an ideal option to overcome the limitation of crop production of the soil and its ability to transfer nutrients into the plant. Foliar application of fertilisers should be considered to strengthen the plant and to help recovering root uptake under the following crop limiting conditions:-

1) When root uptake of nutrients is sub-optimal due to inappropriate soil pH, low soil temperature, poor aeration / soil compaction, water logging.
2) If root activity is disturbed due to disease or pests like nematodes, root grubs, mealy bugs and root aphids.
3) If plant nutrient deficiencies are observed, soil application of fertilisers is inadequate or if nutrient interaction issues limiting the availability of nutrients is present in the soil.

During winter and spring, foliar application of fertilisers should be considered for optimising the level of micro-nutrients in plants and to enhance the quality of feed that is available during calving and lambing periods. Vegetative foliar treatments enriched with chelated micro-nutrients are excellent products for foliar application to increase and maintain pasture quality in a profitable manner. These treatments ensure that stock is provided essential trace elements prior to lambing and calving. Similarly pasture boost treatments are excellent for foliar application to supply nitrogen.

Recovery of plantain crop from multiple nutrient deficiencies with a single foliar treatment – a case study

A plantain crop grown in an irrigated field with an optimum soil pH of 6.3, showed multiple nutrient deficiency symptoms including narrow leaves, sickle and hook leaves, mottling and yellowing on old and young leaves. This crop was growing in patches and most of the plant roots were within a soil depth of 30-100mm. The growth and nutrient uptake of plant roots were affected due to moderate sub-surface compaction and stony nature of the soil.

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Soil and plant analyses were done to assess the possible nutrient deficiencies in the affected area. Plant nutrients including nitrogen, phosphorus, sulphur, magnesium, copper, zinc and manganese were found to be low in the plantain crop. Details of the soil nutrient levels and the plant nutrient levels before and after foliar application are as follows:-

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Based on the soil and plant analysis report, a vegetative foliar fertiliser was formulated and sprayed on the plantain crop. The crop was grazed 10-12 days after the fertiliser treatment. Then another plant sample was taken to assess changes in nutrient levels in this crop, about 45 days after the foliar application. Even after grazing, all the newly grown leaves showed immediate recovery from all nutrient deficiency symptoms and produced more healthy green leaves. The patchy growth gradually disappeared and the new leaves developed after the treatment were 2-3 fold larger than the deficient ones (as seen in the picture above).

The health of the plant and the quality of feed that is supplied to the animal has a strong impact on the health and productivity of the stock. Fodder crops like plantain are a great source of minerals and have an immense potential to enhance feed utilisation and feed conversion in animals. Therefore, depletion of plant nutrients within these plants after repeated grazing needs to be monitored and well maintained. If not closely monitored, such plants will start displaying deficiency symptoms including leaf yellowing, curly leaf tips, narrow little leaves and leaf resetting and die back in severe conditions. Eventually, such crops need to be discarded and replanting of new crops may be required – that is not economically feasible. To avoid such conditions and to improve the longevity of crops it is important to supply the required minerals to these plants for continuous production and enhanced recovery after grazing. Vegetative foliar treatments and pasture boost treatments offered by Outgro Fertiliser Limited have proven to be a very effective way to address nutrient deficiencies and nutrient requirements during the critical stages of growth in plants / crops. Foliar treatments subsequently provide stock with essential trace elements to maximise their health and performance and ultimately enhance the profitability of the farm.