Effect of KN 3 Spry to Flowering Mngo Trees on Fruit Retention, Fruit Size, Tree Yield, nd Fruit Qulity. Steven. Oosthuyse Merenslry Tuhno!ogim! 5 ervicej, P.. ox 14, Duive!sk!oof 835, South fric In South Mric, the mngo cultivrs 'Tommy tkins,' 'Kent,' nd 'Heidi' retin few fruit reltive to the cultivrs 'Senstion,' 'Irwin,' nd 'Keitt.' In the present study, the effect on fruit retention, fruit size, tree yield, nd fruit qulity of inflorescence pplictions of KNO 3to trees of the former cultivrs ws investigted. KN 3 spry t or 4% ws dministered either once during the flowering period, i.e., when the inflorescences were in fullloom, or twice during this period, i.e., when the inflorescences were ctively developing nd susequently when they were in loom. In 'Tommy tkins', the gretest increse in fruit numer occurred following the single ppliction t 4%. In 'Heidi', two pplictions t 4% ech gve rise to the gretest increse, nd in 'Kent', two pplictions t % ech gve rise to the gretest increse. In ech cultivr, slight reductions in verge fruit weight were ssocited with the increses in fruit retention found. In every cultivr, increses in yield occurred. The gretest increses corresponded with the gretest increses in fruit retention found. There ws no pprent effect of the KN 3 sprys on fruit qulity (ground skin colourtion, totl solule solids content, ph, or tste on ripening). Tn South fric, 'Tommy tkins,' 'Kent,' nd 'Heidi,'.l.mngo trees retin few fruit reltive to 'Senstion,' 'Irwin' nd 'Keitt' mngo trees. I<:N 3 folir ppli~ ctions hve een found to enhnce flowering in mngo, nd therey enhnce tree yield (r, 1974; ondd nd Linsngn, 1979). It is noteworthy tht climtic conditions in the regions of the world where I<:N 3 is effective in promoting flowering, often do not ecome dequtely inductive for flowering during the yer. In sutropicl regions, i.e., where winter conditions re sufficiently inductive, flowering enhncement y I<:N 3 hs not een reported. eril pplictions of nutrients to mngo trees hve een found to e ineffective in incresing lef nutrient sttus (McKenzie, 1995). This is proly due to the low sorptive cpcity of the leves. Nutrient ppliction when inflorescences re present my e effective in incresing the nutrient sttus of tree, s the inflorescences my e more cple of nutrient uptke. I<:N 3 spry ppliction to 'Tommy tkins' mngo trees whilst the inflorescences were in fullloom ws previously found to increse fruit retention, to reduce fruit size, nd to increse tree yield nd tree revenue (Oosthuyse, 1993). In the present study, the results of further experiments evluting I<:N 3 eril ppliction to flowering mngo trees re presented. Experiment I (199) In erly ugust, 33 djcent mngo trees were selected in n eightyerold 'Tommy tkins' orchrd t onstnti in the Northern Province (ltitude: 3 4'S; longitude: 3 4'E; elevtion: 457 m; semirid nd sutropicl). Twenty two of the trees were spryed to runoff with I<:N 3 t or 4 % when the inflorescences were in fullloom (ug. ). Supftlm (15 mll 1 1;Plskem, South fric) ws dded to the spry mix. t hrvest in lte Decemer 199, thd'"ruits on ech tree were individully weighe. There were 11 single tree replictes of three tretments (incl. control) in complete rndomized locks design. The dt (tree totls or verges) were sujected to nlysis of vrince. In ech nlysis, the tretment sums of squres ws sudivided for liner nd qudrtic components. The trees were floodirrigted every 1 dys commencing in lte Jnury 199, ech tree ws ferti~ lized with 1 kg of limestone mmonium nitrte, rodcst monthly in three equl pplictions, nd 1 kg of potssium chloride, rodcst monthly in two equl pplictions. Systemic fungicides were spryed on the trees during flowering every 14 dys to control inflorescence diseses, nd copperoxychloride ws spryed on the trees during the fruit develop
ment period every 1 dys to limit disese infection. Insecticides were pplied when required. Experiment II (1993) In midjune 1993, 6 two to threeyerold mngo trees of uniform size nd stge of flowering were selected in ech of three cultivr locks t Mriepskop Estte in the Northern Province Otitude: 4 5'S; longitude: 3 5'E; elevtion: 55 m; semirid nd sutropicl). The trees comprised the cultivrs 'Tommy tkins', 'Heidi', nd 'Kent'. Irrigtion ws scheduled, nd wterstress ws not imposed t ny stge. Five hundred grms of composted chicken mnure supplemented with guno (1%) nd dried kelp (5%), nd 3 g of limestone mmonium nitrte (8% N), were pplied monthly to ech tree. Fungicides nd insecticides were dministered regulrly to control hrmful insects nd pthogens. In ech cultivr lock, KN 3 ws spryed on trees t or 4%, nd one or two pplictions were mde. Single trees served s plots. There were four tretment comintions in complete rndomized locks design comprising 1 locks with five trees in ech. One unspryed tree in ech lock served s control. Sprying took plce when the inflorescences were ctively extending nd susequently when the inflorescences were t 5 to 1% loom when two pplictions were mde. When one ppliction ws mde, the inflorescences were spryed when t 5 to 1% loom. grl 6 ws used s wetting gent (6 ml/1 I HP). fter the period of fruit drop which succeeds flowering, the numer of fruits on ech tree ws counted. t hrvest, the fruits on ech tree were individully weighed. Furthermore, two rndomly selected fruits were tken from ech tree nd plced in well ventilted lortory (within four hours from picking), where they were llowed to ripen t (±lt. These fruits were exmined dily, nd when the surfce of fruit yielded to thum pressure, it ws evluted s follows: Skin colortion ws rted. rting of ws given when signs of skin colourtion were sent, rting of 1 if trnsition to lighter green ws pprent, rting of if regions of the skin hd ecome yellow ut the totl re tht ws yellow exceeded tht totl re tht ws green, nd rting of 4 if the skin ws completely yellow. The skin re covered with redlush ws not considered. To ssess internl qulity, ech fruit ws cut through twice, i.e., longitudinlly long the flttened mrgins of the seed. Juice form ech of the cheeks thus otined ws ssessed for its ph (Mettler 3 ph meter), totl solule solids content (N1, tgo hndheld refrctometer), nd tste. Tste ws rted. rting of 1 ws given if tste ws ppeling, rting of if tste ws stisfctory y not ppeling, nd rting of 1 if tste ws unstisfctory due to the presence of offflvours. The dt (tree totls or verges) were sujected to Tle 1 Mens nd contrst significncelevels (P)for numer tif fruit hrvested, vergefruit weight, nd treeyield. Tretment Numer of verge Tree Yield fruit hrvested fruit weight (kg) (g) Unspryed 5 385 78 % )<NO) 6 366 83 4%KNO) 44 367 9 Heidi 16 14 i3 ";;; " 1 ;:; ~ 1 "5 tt 8 ' ~ 6 E 4 Z" " 18. " 16 ~ " 14 "5 1 tt 1 ti 8 '" E 6 "Z 4 " g ~ 5 "5 tt o 15 ] E 1 "Z control one ppliction two pplictions Potssium Nitrte ppliction Tommy tkins, one ppliction Potssium Nitrte ppliction two pplictions,.,. one ppliction Potssium Nitrte ppliction twopplictions Fig. 1 Effect tif the KN3 sprys on numer tif fruit retined in Tommy tkins' (), 'Heidi' (), nd 'Kent' (). rs with differing letters differ significntly ccording.
Oil :E 5.. ~ 4 "" 3 ~ " <,, Tle Ground skin colourtion, totl solule solids content, ph, nd tste of the smpled Tommy tkins 'fruit oncethey were ripe. Tretment Ground skin TSS ph Tste colourtion (% rix) Unspryed 3.5 15.4 4.8.7 Single ppliction %KNO, 3.7 14.7 4.9.7 4%KNO, 3.4 14.9 4.8.7 one ppliction two pplictions Potssium Nitrte ppliction Doule ppliction % KNO, 3.5 15. 4.9.9 4%KNO, 3.7 15. 4.9.9 Within columns, ll differences were nonsignificnt ccording shown in Tle 1. Liner increses in numer of fruit retined nd tree yield were pprently ssocited with the increse in concentrtion ofkn 3 pplied. Moreover, these increses were pprently ssocited liner reduction in verge fruit weight. Oil :E 5.. ~ 4 ~ one ppliction two pplictions Potssium Nitrte ppliction Experiment II (1993) Slight phytotoxisity ws oserved s in Experiment 1.The effect of the KN 3 sprys on numer of fruit retined is shown in Fig. 1. In ech cultivr, increses were found. In 'Tommy tkins', the gretest increse occurred following the single ppliction t 4%. In 'Heidi', two pplictions t 4% ech gve rise to the gretest increse, nd in 'Kent', two pplictions t % ech gve rise to the gretest increse. Slight reductions in verge fruit weight were pprently ssocited with the increses in fruit retention found (Fig. ). However, only in 'Kent' ws there significnt reduction in verge fruit weight, which followed the two KN 3 pplictions t 4% ech. ' one ppliction two pplictions The effect of the KN 3 sprys on tree yield is shown in Fig. 3. In ech cultivr, increses occurred. Moreover, the gretest increses corresponded with the gretest increses in fruit retention found. Fig. EjJect of the KNO 3 sprqys on vergefruit weight (fruit size) in Tommy tkins' (), 'Heidi' (), nd 'Kent' (). rs with differing letters differ significntly ccording. There ws no pprent effect of the KNO) sprys on ground skin colourtion, totl solule solids content, ph, or tste on fruit ripening in ny of the cultivrs (Tles, 3 nd 4). nlysis of vrince, nd trnsformed when such trnsformtion ws deemed necessry. Experiment I (199) KN 3 ppliction, especilly t 4%, ws slightly phytotoxic to the leves nd inflorescences. The distl mrgins of some to the leves nd the extremities of some the inflorescence rnches ecme necrotic. Mens nd significnce levels for numer of fruit retined, verge fruit weight, nd tree yield re Increses in fruit retention nd tree yield occurred despite ll the trees hving received dequte fertilizer nd wter (vi the soil). s stted previously, KN 3 folir ppliction induces flowering in mngo. KN 3 my thus e considered to hve growth regultory properties in this tree crop (ondd nd Linsngn, 1979). Folir ppliction of growth promoters hs lso een found to increse fruit retention in mngo (hen, 1983; Oosthuyse, 199 S). Incresed nitrogen fertiliztion vi the soil hs, however, lso een found to effect n increse in fruit
Tle 3 Groufld skin colourtiofl, totl solule solids colltellt, ph, nd tste if the smpled Heidi'jmit oncethry were ripe. Tretment Ground skin TSS ph Tste colourtion (% rix) Unspr)'cd 3. 13.9 4..7 Singlc ppliction % KNO, 3.4 14.8 +..7 4%KNO, 3.5 14.8 +..7 8 6 ~ 5 " <3 4 ;.: /}. " 3 Heidi Doulc ppliction % KNO, 3.8 1+.7 +.1.9 +o'okno, 36 1+.5 +..9 control one ppliction two pplictions Potssium Nitrte ppliction Within columns, ll differences were nonsignificnt ccording Tle 4 Grolliid skin colollmtiofl, totl solule solids contellt, ph, nd tste if the smpled 'Kent'jmit once thry were ripe. Tretment Ground skin TSS ph Tste colourtion (% rix) Unsprycd 1.4 18. 4.3.5 Tommy tkins ~ I, Singlc ppliction %KNO, 1.5 18.8 4.3.4 4%KNO, 1.3 18.6 4.1.56 Doulc ppliction % KJ.'\JO, 1.9 19. 4.1.69 4%KNO, 1.9 19.1 4.3.36 Within columns, ll differences were nonsignificnt ccording retention nd tree yield in mngo (Smith, 1994). Hence, 'nutritionl' effect cnnot e discounted. negtive correltion hs een found to exist etween extent of nitrogen fertiliztion or lef nitrogen sttus nd degree of fruit degreening on ripening (Oosthuyse, 1993; McKenzie, 1994; 1995). In the present study, KN 3 ppliction did not effect reduction in degreening. It might thus e considered tht the effect of the KN 3 sprys ws not of sufficient impct to mrkedly increse the trees' nitrogen sttus. The reductions in fruit size rought out y KN 3 might e scried to the enhncements in fruit retention cused. negtive reltionship etween fruit numer nd size in mngo hs een shown previously y the uthor (Oosthuyse, 1995). The results of the present study nevertheless show tht spry ppliction of I 3 to 'Tommy tkins', 'Heidi', or 'Kent' mngo trees whilst they re flowering increses fruit retention nd tree yield without there eing conspicuous reduction in fruit size. It is noteworthy tht ppliction of KN 3 to 'Keitt' nd lso 'Zill' mngo trees ws not found to e eneficil (do, unpulished). This my hve een the result of incresed inflorescence phytotoxicity. It is, 18 17 16 15 14 13 1 ~ II " 1 ~ 9 8 ~ ~ 5 4 3 I o... one ppliction two pplictions Potssium Nitrte ppliction, ~ ~ one ppliction two pplictions ====i' Fig. 3 Effictif the KN3 sprqys on treeyiefdin Tommytkills' (), Heidi' (8), nd 'Kent' (). rs with differing letters differ significlltiyccording. dvised tht the effects of KN 3 ppliction e evluted on cultivrs other tht those used in the present study efore commercil recommendtions re mde for these cultivrs. Gustv vn Veijeren nd the stff of Mriepskop Estte (Merensky Holdings) re thnked for their coopertion. Lesley Mnym nd ennet Mmol re thnked for dt collection.
R, R. 1974. Induction of flowering of the mngo y chemicl spry. rop. Sri. Soc. Proc. 5:154 16. ONDD, N.D. ND M.E. LINSNGN. 1979. Flowering in mngo induced y potssium nitrte. Hort.Sci. 14:5758. HEN, WS. 1983. ytokinins in the developing mngo fruit. Plnt Pl?Jsiol.71:356361. MKENZIE,. 1994. The ckground skin colour of exported mngo fruit in reltion to tree nitrogen sttus. S.. Mngo Growers' ssoc. Yerook 14:68. MKENZIE,. 1985. The effect of clcium nd potssium folir nd fruit sprys on Senstion mngo lef nutrient concentrtions nd fruit qulity. S.. Mngo Growers' ssoc. Yerook 15:4447. MKENZIE,. 1995. Field survey method of determining mngo lef norms. S.. Mngo Growers' ssoc. Yerook 15:485. OOSTHUYSE, S 1993. Effect of spry ppliction of KN3, ure, nd growth regultors on the yield of Tommy tkins mngo. S.. Mngo Growers' ssoc. Yerook 13:586. OOSTHUYSE, S.. 1993. Ripening ehviour nd qulity on ripening of Senstion mngo in reltion to coldstorge temperture nd tree fertiliztion. S.. Mngo Growers' ssoc. Yerook 13:6775.. OOSTHUYSE, S.. 1995. Effect of postloom queous spry ppliction of G3, N nd PPU on fruit retention, fruit size, nd yield in Tommy tkins nd Heidi mngo. S.. Mngo Growers' ssoc. Yerook 15:3133. OOSTHUYSE, S 1995. Effect of time nd severity of fruit thinning on fruit retention, fruit size, tree yield, nd tree revenue in Senstion mngo. S.. Mngo Growers' ssoc. Yerook 15:3438. SMITH,.L. 1994. Optiml lef nitrogen norms for young nd old mngo trees (cv. Senstion). J. S. Soc. Hort. S?i. 14:4548.