CROP yield in Pakistan is not satisfactory due to improper fertilizer management. Balanced nutrients are paid little attention. Its deficiencies emerge in the farmer’s field and are recognized as the symptoms on foliage and reduction in the quality and yield.
Foliar fertilizers are being used in vegetable and fruit crops that contain various macro and micronutrients. This technology has come under use but is not common.
Foliar fertilizers immediately deliver nutrients to the tissues and organs of the crop. This is a practice of applying liquid fertilizers to leaves. The leaves are green factories where photosynthesis produces compounds needed for growth. These are absorbed right at the site they are used acting fast. For instance, 80 per cent of the phosphorus applied through conventional fertilizers may get fixed up in the soil but up to 80 per cent of the foliar-added phosphorus is directly absorbed.
Bhonde et al. (1995) evaluated the effect of zinc, copper and boron on onion crop. Bulb size and yield and quality of bulb enhanced when micronutrients were applied in combination instead of alone. The foliar application of zinc three ppm, copper one ppm and boron 0.5 ppm gave maximum net return to the growers
Pascua, et al. (1996) applied Green Bee All Purpose and Growth Booster foliar fertilizers to explore the possibility of substituting soil applied fertilizer with foliar on garlic plants. They reported that the plants fertilized with ½ fertilizer recommendation and supplemented with Green Bee All Purpose + Growth Booster were tallest, most vigorous, produced heaviest bulbs and gave the highest yield per hectare.
Naruka and Singh (1998) applied two concentrations of urea sprays (1 and 2 per cent) and three concentrations of gibberellic acid (GA3) spray (50, 100 and 150 ppm); both urea and gibberellic acid application enhanced the growth and fruit yield of okra significantly. Tumbare, et al. (1999) applied NPK at recommended rate as solid fertilizer and as liquid fertilizer; the yield and yield component values increased with increasing fertilizer rate by liquid as compared to conventional application.
Whereas, Palaniappan et al. (1999) applied N and K fertilizers (100 and 75 per cent of recommended rate), Multi-K and Polyfeed (Both at one per cent) foliar fertilizers and the combination of these two on tomato crop. The application of 100 per cent NK + two sprays of Polyfeed (30 and 45 days after sowing, DAS) + three sprays of Multi-K (60, 75 and 90 DAS) gave the highest tomato fruit yield, marketable yield, net income and benefit cost ratio.
Similarly for chili, the treatment of 100 per cent NK + three sprays of Polyfeed + two sprays of Multi-K produced the highest number of fruits per plant, dry fruit yield, net income and benefit cost ratio. Increasing the frequency of Polyfeed spraying from three to four times do not increase the number of chilli fruits per plant. Souza et al. (1999) applied kumulus (containing sulfur) at four kg/ha to see the effect on cotton crop. Treatments with increased sulfur produced 11.5 per cent more cottonseed then the untreated control.
Naruka et al. (2000) studied the effect of foliar application of zinc and molybdenum through foliar spray at 0.2, 0.4 and 0.6 per cent and 30, 60 and 90 ppm, respectively. Increasing zinc and molybdenum levels resulted in increasing plant height, number of fruits, fruit diameter and fruit yield.
However, increasing levels resulted increasing in growth and height fruit yield. Selvi and Rani, (2000) reported that okra plants were treated with NPK (40: 50: 30 kg/ha) alone, NPK + micronutrients (MNS; soil application of FeSO4 at 50 kg/ha and Zn SO4 at 25 kg/ha, or foliar spraying of FeSO4 at 1.0 per cent and ZnSO4 at 0.5 per cent) or foliar and soil application of micro food (SMF, 750 and 25 kg/ha, respectively).
The highest yield, income and benefit cost ratio were recorded from NPK+SMF and MNS foliar treatment; whereas, lowest yield among the treated plants was recorded from the single NPK treatment.
Barge (2001) used the foliar fertilizers, ElamMax (27 per cent Mn) at 0.5 pints/acre, Folizyme (12 per cent N, three per cent K, three per cent Ca and three per cent Mn) at 2q/acre, Keylate (five per cent Mn) at two pints/acre, White Label (six per cent Mn) at 2 pints/acre and Harvest More Urea Mate (N, P, K, Ca, Mg, B, Co, Cu, Mn, Mo and Zn) at 5 ponds/acre.
All treatments resulted in higher yields of soybean than the control. Bajapai and Chauhan (2001) worked on effect of zinc, boron and manganese and reported that all treatments significantly improved the performance of okra in terms of number of fruits per plant, fresh and dry fruit weight, seed per fruit and seed weight.
Singh, et al. (2002) reported that bulb diameter, bulb size index, total soluble solids, dry matter weight 20 bulbs, and gross and marketable yield of onion were highest with basal application of NPK and foliar application of 1% Multi-K 30, 45 and 60 days after planting.
Katkar et al. (2002) conducted an experiment to study the effect of foliar sprays of nutrients and chemicals on yield and quality of cotton. Results indicated that the foliar application of different nutrients and chemicals significantly increased seed cotton yield by 38.7, 37.1, 31.3 and 21.2 per cent over control.
Naresh and Singh (2002) conducted study on the effect of zinc (0.2, 0.4 and 0.6 per cent), copper (0.1, 0.2 and 0.3 per cent) and boron (0.1. 0.2 and 0.3 per cent) on the yield components of litchi plants and observed significant improvement in fruit set, normal fruit, cracked fruits and fruit maturity in the treated plants over control.
Mishra et al. (2003) also observed significant improvement in chlorophyll content and fresh weight of kinnow treated with zinc, iron and boron. Chattopadhyay et al. (2003) applied B at 0.28, 0.56 and 1.12 kg/ha and Mo at 0.1, 0.2 and 0.4 kg/ha alone or in combination (as single or double) to okra cv Pusa Sawani in field experiment. Mo at 0.4 kg/ha resulted in the highest yield of 223.18 q/ha, while B at 0.56 kg/ha produced the highest yield of 222.71 q/ha. B at 1.12 kg/ha + Mo at 0.2 kg/ha produced the highest yield of 229.37 q/ha.
Alkaff and Hassan (2003) determined the effect of foliar application 0,two,four, 6g of power four on the growth and yield of okra plants. Foliar application of 4g of power four/litre had the highest value for fresh and dry weight, number of pods per plant, average yield, average pod weight and early yield.
Sharaf and El-Naggar, (2003) conducted field experiment to record the response of carnation plant to phosphorus and boron foliar fertilization. The results showed that foliar application of P2O5 alone or in combination with different levels of B stimulated the length, diameter and dry weight of stem, number and dry weight of leaves per branch as well as enhanced flowering time, number, size and dry weight of flower per plant. The best results of vegetative growth and flowering characteristics were obtained at 200 mg P2O5 per litre plus 50mg B per litre.
Tuncay et al. (2004) investigated the effects of Superalg, NZN, Croptec and Polyfeed foliar fertilizers on yield and quality related characters of sunflower. They had significant effects on seed yield, seed height, seed/husk ratio, oil content, plant height, seed dry matter and stem yield (P0.01).
The best results were obtained from Croptec and Polyfeed fertilizers. However, according to economic analysis, NZN application had the highest gross margin per hectare. Alexander, et al. (2004) applied Boron (B) through Disodium Octaborate Tetrahydrate (DOT) in the form of Solubor as foliar spray @ 1.5g/l twice at 15 days interval and calcium (Ca) through Calcium Nitrate (CN) as Hydro Calcium Nitrate as soil application to supply top dressed N, twice @ 30 kg/acre. Among the various treatments, foliar spray of DOT with soil application of CN gave maximum yield of 20.93 t/acre and had a long shelf life of 12 days in comparison to control where yield of 16.63 t/ac and a shelf life of four days were recorded.
However, many other experiments were carried out on the effect of commercial foliar fertilizers alone and in combination with recommended NPK levels, on growth and yield potential of different crops. The results showed significant differences with reference to the data recorded on days taken to flowering, plant height, number of branches per plant, number of fruits per plant, fruit length, fruit weight per plant, fruit yield per hectare, fruit quality and cost benefit ratio.
Deficiencies of micronutrients were emerged in most of the farmer’s fields due to little attention; but very little work has been done locally on commercial foliar fertilizers.
Growers are advised to use or include foliar fertilizers in combination with recommended NPK for obtaining healthy, early and high yielding crop with good fruit quality.
The researchers are also suggested to conduct further experiments on all available foliar fertilizers and also research required to test other aspects of these products alone and in combination with NPK on growth and yield parameters of crops under agro-ecological conditions of Pakistan.