Effect of foliar spray of ammonium nitrate and irrigation time on vegetative growth, fruit set, yield and fruit quality of “Ewais” mango trees

Background The current experiment was done during the 2018 and 2019 seasons on ‘Ewais’ mango trees ( Mangifera indica ) grown in Research Station, El-Nubaria district, Egypt, to study the impact of spraying ammonium nitrate (NH 4 NO 3 ) and irrigation time on vegetative growth, yield and fruit quality. All experimental plants have been received the same care, i.e. control of pests & weeds, fertilization, and irrigation until the 1st week of October. The irrigation was adapted to apply 5m 3 /feddan (4200 m 2 )/week to control leaves damage due to low temperature after this period and the treatments included: (T1) Water spraying at 1st week of November + start normal irrigation program at the same time after four weeks of adapted irrigation as 5m 3 /feddan (4200 m 2 )/week (Control). (T2) Spraying with NH 4 NO 3 2% at 1st week of November + start normal irrigation program at the same time after four weeks of adapted irrigation as 5m 3 /feddan /week. (T3) Spraying NH 4 NO 3 2% at 1st week of November + start normal irrigation program at 1st week of December after eight weeks of adapted irrigation as 5m 3 /feddan/week. (T4) Spraying NH 4 NO 3 2% at 1st week of November + start normal irrigation program at 1st week of January after twelve weeks of adapted irrigation as 5m 3 /feddan/week. All treatments received the same quantity of irrigation water, approximately 4000 m 3 /feddan/year. Results All treatments (T2, T3 & T4) had a significant influence on vegetative growth, fruiting behavior (fruit set % & the yield), and the fruit quality compared with the control (T1). The significant was not only the fruit physical characteristics (weight, dimensions, volume, and specific gravity) but also the fruit chemical characteristics (total soluble solids % (T.S.S.), acidity %, T.S.S / acid ratio and vitamin C (L- ascorbic acid)). Conclusion Spraying NH 4 NO 3 2% at 1st week of November plus start normal irrigation program at 1st week of November or December or January after 4 or 8 or 12 weeks of adapted irrigation as 5m 3 /feddan (4200 m 2 )/week (T2, T3, and T4) increased the vegetative growth, i.e. length of terminal shoots, No. leaves / terminal shoots & leaf area as well as the fruiting behavior such as fruit set percentage, No. fruits per tree & the tree production (kg/tree) and improved the fruit characteristics not only the fruit physical parameters but also the chemical properties in comparing with the untreated trees. During the two seasons, spraying NH 4 NO 3 2% at 1st week of November plus start normal irrigation program at 1st week of January after 12 weeks of adapted irrigation as 5m 3 /feddan/week (T4) is recommended since; it is the only treatment with the superiority effect on studied parameters.