From the above review on fertigation experiences of the selected fruit crops, viz. apple, banana and citrus, inferences have been drawn and given in brief below:
Apple
Fertigation with trickle and broadcast: Studies were done on a compound
solution 19:6:6 NPK fertilizer applied in trickle irrigation annual fertigation between 10 8g N/tree and compared with irrigation broadcast fertilizer at 80 g N/treeand no fertilizer and irrigation. In the initial days there was not much difference in shoot growth among
different treatments. Fertigation at 40 and 80 g N/tree caused large increase in total shoot growth associated with an excessive production of axillary floral buds. The best balance between increased shoot growth and fruit bud production, fruit set and cumulative yield was achieved with fertigation at 20gN/tree.
Microsprinkler and fertilizer application : The apple tree growth was studied
at 2 levels of potassium (0 and 200 kg/ha) and 2 irrigation schemes, without irrigation in 4 blocks and with irrigation which permits soil moisture in root zone as 25-35 kg/ha of soil moisture head. Irrigation was given in half the area (4 blocks). Significant influence of potassium at the level of 200 kg/ha on increase of soil moisture pressure head was found both for irrigated and non-irrigated blocks. A significant effect of microsprinkler on lowering by ratio of 2.5 of the contents of NO3 form in groundwater in irrigated blocks was found as compared to unirrigated blocks.
Subsoil drip irrigation and nitrogen application: Studies on apple cv. Granny
Smith, Smoothee and Koop 10 were done by drip irrigation and subsoil irrigation with nitrogen applied either in the irrigation water or by topdressing. The rate of watering was 100 per cent of evapotranspiration loss and amounted to 161 cubic m/ha. No significant differences were observed between the two methods of irrigation. However, with subsoil irrigation some blockage were observed in the pipes during the ninth growing season which resulted in lower yield and poor fruit quality.
K deficiency correction through fertigation: Fertigation cv. Mc Intosh, 40 g N
and 17.5 g P/tree by the third growing season with leaf K average 0.82 per cent dry mass suggesting deficiency of K. This coincided with extractable soil K concentrations of 50-60 g/tree soil in a narrow volume of coarse textured soil located within 0.3 m of the emitters. The decrease in leaf K was reversed and fruit K increased after applications of 15-30 g K/tree as granular KCl directly beneath the emitters in spring or as KCl applied as fertigant in irrigation water. K fertilizers improved fruit surface colour, size and titratable acidity when leaf K was less than 1. Fruit calcium and incidence of bitter pit or core flush were unaffected by K applications.
Microjet/drip/sprinkler irrigation and fertigation : Study on influence of fertilizers
(ammonium nitrate, urea and mono ammonium phosphate) and irrigation methods, (microjet, drip and sprinkler) on apple cv. Macspurl trees on MM-106 rootstock in Canada showed that there was no difference in growth and yield between untreated control and urea applied as a foliar spray (1 kg/100 litres of water). Trunk cross- section area and yield were lower for trees watered by microjet (2-3 hr/day) and drip (21.6 hr/ day) compared with those receiving 2 duration of sprinkler irrigation (1.5 or
Land and Nutrient Management in Precision Farming
3 hr every 7 days). No differences were obtained between microjet and drip irrigation or between two durations of sprinkler irrigation for trunk-cross-sect and fruit yield.
Fertigation with drip and flooding : Work on nutrient management in apple
carried out through trickle irrigation in Solan, Himanchal Pradesh (India) on cv. Mollie's Delicious with the recommended doses of NPK under drip irrigation, emitters broadcasting. For broadcasted fertilizer treatments, plots were irrigated either by basin irrigation or without irrigation. Placement of fertilizers under the emitters resulted in less leaching of N and better distribution of K to 60 cm soil depth. With basin flooding the nutrients leached down below this depth where they were no longer available to the plants.
Fertigation, fertilizer broadcasing and mineral content : Results of fertigation
on mineral composition and colouration in cv. Elstar and Boscoon in Germany showed that no differences were found in firmness, acidity, sugar content and their changes between fertigated and unfertigated plots. It was found that fertigation did not improve fruit mineral content with respect to their storage potential. The reduction in nitrogen level applied by fertigation did not affect fruit colour. Fertigation had no positive effect on flowering and productivity. Drip irrigation plus broadcast fertilizer application, gave the best yield.
Banana
Fertigation, drip and micro-spray: Field experiments were carried out on
fertigation by drip and micro-spray irrigation at weekly and monthly intervals and it was observed that yields were higher with micro-spray application for both fertigation methods. Yield was also higher with monthly application compared to weekly applications. It was concluded that fertigation should be done at monthly intervals rather than weekly for both the methods.
Drip, basin irrigation, NK and yield: Drip irrigation of Cavendish banana in a
sandy clay loam soil gave better performance than basin irrigation. Different levels of evaporation replenishments and N and K gave significantly higher yield with drip irrigation (83.8 tonnes/ha) as compared with 78.9 tonnes/ha for basin irrigation. Increasing N had no significant effect on water-use efficiency but increasing K had some effect.
Drip,water and fertilizer regimes : Different water amounts through drip irrigation
regimes were studied where amount were fixed according to the evaporation factor from a class A pan, the fertilizer regimes consisted a fixed dose, once a week and constant concentration of fertilizer injected into the irrigation water throughout the
irrigation season. The increased water amount lead to an increase in sucker height, earlier flowering, more branches and also increase in average bunch weight. Maximum effects were observed in suckers irrigated at f =1.4 but any increase above f =1.0 gave non-significant advantage.
Drip and surface irrigation and fertilizer application : Effect of water-soluble
fertilizers comprising 2 fertilizers sources, 3 levels and 2 planting systems were studied, and compared with surface method of irrigation using straight fertilizers. The fruit yield was significantly higher in normal planting (82.86 tonnes/ha) than paired row planting (75.75 tonnes/ha). The fruit yield increased in water-soluble fertilizer (81.01 tonnes/ha) compared to only nitrogen through drip (77.59 tonnes/ha). Minimum fruit yield was observed in surface method. (72.61 tonnes/ha). The water saving was 50 per cent under drip irrigation compared to surface method.
Citrus
Drip, microjet and fertigation : Research on Mid knight Valencia oranges in
South Africa with various fertigation frequencies and conventional hand fertilizer application practices resulted in no statistical difference between treatments in respect of yield and fruit size. Stem circumference was greater in double line drip treatment with fortnightly fertigation. Trees under single line drip fertigation had higher TSS, acid and juice content than other two treatments.
Drip, lateral numbers and fertilizer application : Studies on 10-year-old Mineola
Tangelo grown in Israel with micro-sprinkler or trickle irrigation from 1 or 2 drip laterals per tree and N fertigation (100, 200 and 300 kg/ha) showed decreased fruit growth. The fruits of the stressed tree were smaller with higher sugar content. Low N rate (100 kg N/ha) caused a gradual decline in fruit yield and in leaf N content but produced large fruits with thinner rinds. Trickle irrigation with two laterals, had better tree growth and higher yield than trickle irrigation with one lateral.
CMIS irrigation automation and expert system model : Citrus management
irrigation system (CMIS) based on soil moisture sensors and automated weather station was developed to assist microirrigation and fertilizer management. The system integrates an expert system conventional control, a crop water requirement simulations model databases and irrigation management tools into a single system to assist the decision- making processes by irrigation managers. The system is highly automated and has the potential to improve microirrigation management to achieve water and energy savings and to prevent water pollution due to improper fertigation management.
Land and Nutrient Management in Precision Farming
Drip, microjet and NPK fertigation : Study on drip and microjet sprays on 25-
year-old orchard of cv Shamouti oranges with small volumes irrigation by drippers combined with a high concentration of NPK equivalent to half the strength of Hoagland solution resulted in the highest yield. The increased yield was due to more number of fruits/ha. The low volumes irrigation combined with high concentrations of NPK produced restricted root growth and dense root system with more number of small roots. There was no treatment effects on fruit quality or leaf water potential.
REFERENCES
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