Scientia Hrticulturae, 3 (1975) 89--94 Elsevier Scientific Publishing Cmpany, Amsterdam -- Printed in The Netherlands EFFECT F NITRGEN FERTILIZATIN N YIELD AND FRUIT IL CNTENT F AVCAD TREES A.B. ABU AZIZ, I. DESUKI and M.M. EL-TANAHY Natinal Research Centre, Dkki, Cair (Egypt) (Received May 27th, 1974) ABSTRACT Abu Aziz, A.B., Desuki, I. and E1-Tanahy, M.M., 1975. Effect f nitrgen fertilizatin n yield and fruit il cntent f avcad trees. Scientia Hrt., 3: 89--94. This wrk was carried ut t study the effect f tw nitrgen levels, 250 and 500 g f actual nitrgen per avcad tree per year. The nitrgen surces were calcium nitrate (as sil applicatin) and urea (as fliage applicatin). Nitrgen fertilizatin gave a highly significant increase in tree yield (kg/tree) in mst treatments. Mrever, urea sprays seemed t be mre effective n the yield than calcium nitrate added t the sil at the same nitrgen level. The 500 g nitrgen level f bth surces gave a higher yield increase than 250 g nitrgen. Nitrgen fertilizatin gave a slight increase in mean avcad fruit weight and size, while urea sprays seemed t be mre effective in increasing the mean fruit weight and size. A slight decrease in flesh il cntent ccurred as a result f nitrgen fertilizatin. INTRDUCTIN Avcad (Persea americana, Mill} is cnsidered t be a gd surce f minerals and vitamins (Kay, 1964). The fruits are generally used in sme cuntries as an appetizer r salad (Rberts, 1955). Blasberg {1953) mentined that urea spraying increased the yield f apple trees. Lynch et al. (1954) fund that variatins in nitrgen level appeared t have a direct effect n the yield f fur avcad cultivars. El~Tmi et al. (1968) reprted that high levels f nitrgen fertilizatin caused a significant increase in the yield f 'Chemiali' live during the ff*seasn, abut 265% ver the cntrl, while nitrgen fertilizatin did nt affect flesh il percentage. De la Rcha and Flres (1955) fund that fliage sprays with Nu*green slightly imprved fruit size in yung avcad strawberries and in ranges. Maxims et al. (1969), wrking n mature 'Baladi' guava, reprted that the additin f nitrgen increases fruit weight and size. The aim f the present wrk was t study the influence f nitrgen fertilizatin as urea spray r sil applicatin n the yield and il cntent f fruits f avcad trees. Reprinted with permissin frm ELSEVIER, Inc. Scientia Hrticulturae hmepage: http://www.sciencedirect.cm/science/jurnal/03044238
90 TABLE I Differential treatments used Treatment Actual Fund in: N. f applicatins Time f nitrgen fertilizatin per tree (g) Calcium Urea nitrate spray (kg) (kg) Cntrl 0.0.... N 1 250 1.60 0.54 2 March and April N~ 500 3.20 1.08 4 March, April, May and June MATERIALS AND METHDS The materials used in this investigatin were 15 'Fuerte' avcad trees, budded n 'Fuerte' rtstck at Seds rchard which belngs t the Ministry f Agriculture. The trees were abut 24 years ld, planted in clay lam sil, and were vigrus and as unifrm as pssible. A cmpletely randmized design was fllwed. The selected trees were treated accrding t the usual farm management except fr the nitrgen fertilizatin. The treatments are mentined in Table I. Each tree als received abut 100 kg f balady manure during the winter mnths. Trees treated with urea were given drenching water spray cntaining the 270 g f urea disslved in 27 l f water. Fruits f each individual tree per treatment were recrded at the cmmercial harvesting time. A sample f 20 fruits fr each tree was used fr the determinatin f the fruit weight, fruit size and il cntent. RESULTS AND DISCUSSIN Yield. -- Data cncerning the yield in kg/tree are shwn in Table II (left part). Fr the first seasn, all levels f fertilizatin f the nitrgen surces caused an in~rease ver the cntrl trees. The maximum increase in yield was abut 40% which resulted frm 500 g nitrgen in the frm f urea sprays. Als, there was abut 34% increase in yield due t 500 g nitrgen as sil applicatin f calcium nitrate. Trees sprayed with 250 g nitrgen as urea gave abut 31% increase ver the cntrl. The nly nmsignificant treatment was 250 g nitrgen as sil applicatin, the increase ver the cntrl being abut 13%. In the secnd seasn all levels f nitrgen surces caused highly significant increases ver the cntrl. The maximum increase was abut 122% which resulted frm 500 g nitrgen in the frm f urea sprays. The sil applicatin at the same nitrgen level caused abut 93% yield increase ver the cntrl. Fr the 250 g nitrgen level, abut 86% and 32% increases ver the cntrl were
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93 due t urea sprays and sil applicatin, respectively. Frm the abve data urea sprays seemed t be mre effective than sil applicatin (with equal amunts f elemental nitrgen) in bth seasns. Als, trees receiving 500 g f nitrgen frm either surce gave higher yields than the trees receiving 250 g. Cmparing the yields f the tw seasns, it becmes evident that the yield f the first seasn was higher than that f the secnd seasn. This same trend ccurred in the cntrl trees and indicates that 'Fuerte' may be an alternate bearer. If this is true, then ne can say that the high level f nitrgen fertilizatin nt nly increased tree yield, but als reduced the effect f alternate bearing. These results are in agreement with thse reprted by Blasberg (1953), Lynch et al. (1954) and El~Tmi et al. (1968). il cntent. -- Table II (right part) shws that the effect f nitrgen fertilizatin treatments either as urea spray r sil applicatin n the flesh il cntent was rather slight. This was true in bth seasns. Hwever, there was a slight but nn-significant decrease in bth seasns. These results are in agreement with thse reprted by E1-Tmi et al. (1968). Fruit weight and size. -- Data in Table III illustrate that in the first seasn the weight and size f fruit frm trees given the sil applicatin (calcium nitrate) were nt much different frm thse f the cntrl trees, while trees sprayed with urea had larger fruits. In the secnd seasn (light crp) all treatments including the cntrl reflect a superirity in fruit weight and size cmpared with the first seasn. All treated trees in this year had significantly bigger fruits than the cntrl trees, except thse receiving 250 g f actual nitrgen as sil applicatin. Urea sprays seemed t be little better than calcium nitrate as sil applicatin as far as fruit weight and size are cncerned. These results are in agreement with thse reprted by De la Rcha and Flres (1955), and Maxims et al. (1969). ACKNWLEDGEMENT The authrs wuld like t express hw deeply grateful they have been t the late Prfessr Dr Zakaria Zidan under whse supervisin this wrk was cmpleted. His kind help and fruitful advice have been very much appreciated. REFERENCES Blasberg, C.H., 1953. Respnse f mature McIntsh apple trees t urea fliar sprays in 1950 and 1951. Prc. Amer. Sc. hrt. Sci., 62: 147--153. De la Rcha, G.G. and Flres, C.D., 1955. Tests n nitrgen fliar nutritin. Inf., mens. Estac. Exp. Agric. La Mlina, 29(332): 5--9 (Hrt. Abstr. 1956, Vl.26, N.976) EI-Tmi, A.L., El-Mahdi, M.A. and Nur, G.M., 1968. Effect f nitrgen fertilizatin n prductivity f Chemlali live tree at Burg El-Arab area. Extrait du Bulletin de L'Institut du D~sert d'egypte, T.XVI, N.2, pp. 135--147
94 Kay, D.E., 1964. The Prductin and Marketing f Avcad Pears. Trpical Prducts Institute N.G.3. Lndn, 17 pp. Lynch, S.J., Gldweber, S. and Rich, C.E., 1954. Sme effects f nitrgen, phsphrus and ptassium n the yield, tree grwth and leaf analysis f avcads. Prc. Fla. Stn. hrt. Sc., pp.220--224. (Hrt. Abst. 1955, Vl.25, N.3166) Maxims, E.M., Zidan, Z., E1-Barkuki, M.H. and E1-Bana, G.I., 1969. Effect f Fertilizatin n Yield and Quality f Guava Fruits. Res. Bull. 350, Ain Shams Univ. Fac. Agric. Shubra. El. Kheima, Cair, 16 pp. Rberts, E.W., 1955. Fruit and Vegetable Facts and Pinters. Avcads. Secnd Revisin. United Fresh Fruit. Vegetable Assc. Washingtn, D.C., 10 pp.