Review of Avocado Fertilizer Practices In San Diego County

Transcription

1 Cmprehensive Study Review f Avcad Fertilizer Practices In San Dieg Cunty cmplete fertilizer injectin '''''>TOlm is shwn here. The tanks in the frer;:s.ij;r und huse the fertilizer and the : units belw are the injectin cmpnents. Dispensing liquid fertilizers has been made simple with these sphisticated systems. by C. Dn Gustafsn San Dieg Cunty Farm Advisr Avcad fertilizatin is perhaps the mst cntrversial cultural practice the grwer encunters as he attempts t maintain a successful grve. There are tw explanatins fr this situatin ; 1) many different types f material are n the market- bth rganic and inrganic fertilizers and 2) every persn in the industry seems t have his wn special frmula t increase prductin and secure lucrative yields. 10 AVOCADO GROWER Sils Mst f the avcad sils in San Dieg Cunty are decmpsed granite. The sil series that avcads are mst cmmnly planted in are Vista Sandy Lam, Fallbrk Fine Sandy Lam and Cieneba carse sandy lam. The ph f these series is frm 6.0 t 7.2. The nutrient level f nitrgen, phsphrus, ptassium and zinc is relatively lw cmpared t ther sil types in Califrnia. Since these sils are deficient in nitrgen, this element must be applied t the sil and trees each year. In additin, phsphrus, ptassium and zinc levels are becming deficient and these elements are being used mre as hillside grves are planted in shallw sils. Avcad trees, like ther plants, require mineral nutrients fr grwth and prductin. These nutrients are btained frm the sil by the rt system f the tree. After a tree has grwn in the sil fr sme time, sme f these mineral nutrients may becme depleted r, fr ther reasns, the rts may be unable t btain enugh t supply the trees. Fertilizers must be applied t vercme the deficiencies.

2 ------Chart st Year - 1 Tablespn f cmmercial fertilizer (ammnium nitrate, etc.) every third irrigatin 2nd Year pund elemental nitrgen in split 3rd Year - 1/4 pund elemental nitrgen in split 4th Year - 1/2 pund elemental nitrgen in split 5th Year - 3/4 pund elemental nitrgen in split 10th Year - 1 pund elemental nitrgen in split 11th - 20th Year - 1-1/2 t 2 punds elemental nitrgen in split Avcad trees are shallw rted with 80 t 90 percent f their rt system in the first tw feet f sil. Because f this shallw rting, it is pssible fr the rts t btain any nutrient element that is present in the upper prtin f the sil prfile. Als, avcad trees are gd fragers and frequently pick up the required amunts f nutrients fr desirable plant grwth. Lng-term experimentatin and experience in the field indicates the fllwing nutrient elements must be applied t avcad trees in San Dieg: 1) Nitrgen, 2) Zinc, 3) Phsphrus and 4) Ptassium. Nitrgen Nitrgen is the mst widespread element deficiency in San Dieg Cunty avcad rchards, and nearly all grves require sme nitrgen fertilizatin each year t maintain nrmal yields. The amunt f nitrgen required by avcad trees will vary accrding t variety and age. Fr instance, Hass trees require up t twice the amunt f nitrgen that ther varieties, such as Fuerte, Bacn and Zutan need. Chart 1 is a schedule guide f nitrgen dsages (per tree) needed by avcad varieties ther than Hass: Nitrgen can be best applied in a chemical frm. Materials such as calcium nitrate (15% N), ammnium nitrate (33 % N) and urea (46% N) can be used in an efficient fertilizer prgram. A change, r rtatin, f materials abut nce a year is suggested. Extensive use f acidfrming residue materials like ammnium nitrate and urea will cause a lwering f the sil ph t what culd be a harmful level. It is recmmended that these materials be alternated each year with calcium nitrate t avid this situatin. The shallw, infertile sils fund n the hillsides f San Dieg Cunty will benefit with the applicatin f rganic materials--bulky rganics like straw r manure, and cncentrated rganics like bld meal r fish meal. Bulky rganics are less expensive, but their nutrient cntents are much less than the cncentrated rganics. Chart 2 prvides examples f bulky rganic, cncentrated rganics and inrganic material Chart Bulky Organic Materials Kind Dairy Manure Steer Manure Hrse Manure Pultry Manure Kelp Cncentrated Organics Bld Fish Meal Tankage Urea Inrganic Materials Calcium Nitrate Ammnium Nitrate Ammnium Phsphate %N % P % K Chart Amunt (punds)/tree/mnth Age f Trees Urea Ammnium Nitrate Calcium Nitrate Organic materials can be applied anytime during the year, but fall is ptimum. Cautin shuld be exercised in applying rganic matter t avcad trees. D nt apply the material t heavily t the sil; a heavy cver f rganic material culd cause the rts t becme suffcated since xygen is very imprtant t rt activity and peratin. If a heavy applicatin f rganic matter is made at ne time, it culd exclude air frm the rts causing damage t the trees. Nitrgen can be applied twice a year, usually in February and July. Fertilizing is nt recmmended during the blssum and fruit-setting perid f March t June. These recmmendatins are fr hand applicatin t rchards under fixed r rtating sprinklers. Chart 3 shws the suggested amunts f nitrgen t inject int a drip irrigatin system. Nitrgen-deficient trees will shw light green leaves, yellw veins, lack f vegetative grwth, small leaves, reduced yields and premature leaf drp. Phsphrus & Ptassium During the last few years there has been decreasing levels f phsphrus and ptassium bserved in many leaf analyses frm San Dieg Cunty avcad rchards. The granitic sils, inherently deficient f these tw elements, cupled with the withdrawal f these nutrients by the avcad plant, results in lwer leaf levels. Varius frms f phsphrus and ptassium are available. They can be applied singly, tgether r in cmbinatin with nitrgen. Sme f these materials are: ammnium phsphate (16-20), treble superphsphate, triple 15 ( ), ptassium sulfate, etc. next page AVOCADO GROWER 11

3 Cntinued frm page 11 Since nitrgen and ptassium materials are sluable in water, these materials can be applied thrugh an irrigatin system. Phsphrus materials that have nt been acidified, hwever, cannt be used in an irrigatin system where the highcalcium Clrad River water is used. If the phsphrus material is nt acidified, a precipitate will frm causing a clgging f the irrigatin system. Mixed fertilizer f nitrgenphsphrus-ptassium can be applied in the same manner as with nitrgen alne. The amunt f material will be gverned by the nitrgen dsage required. If an N-P-K slutin is used in an irrigatin system, either sprinkler r drip, the slutin shuld be acidified sufficiently t cunteract the highcalcium cntent in the Clrad River water. If nitrgen fertilizatin is accmplished by injecting int a drip irrigatin system thrughut the year, then phsphrus and ptassium can be applied t the sil in the fall. The winter rainfall will take these materials int the rt zne. There has been n leaf r tree grwth symptms determined relating t a phsphrus r ptassium deficiency. Leaf analysis is the nly knwn way t determine if there is a phsphrus r ptassium deficiency. Zinc Zinc deficiency, usually referred t as Mttle Leaf, ccurs cmmnly n avcad trees. It is the ne micrnutrient element mst ften recgnized as being deficient. A nutritinal prblem, this deficiency causes reduced tree vigr and lwer yields. If nt crrected, the tree may die frm lack f zinc. Symptms f Mttle Leaf are: 1) Light yellw (chlrtic) areas between the veins, starting at the margin f the leaf and extending t the mid-rib and base; 2) Small and narrw leaves; 3) Pear-shaped fruit becmes val t rund, and smaller than nrmal as deficiency becmes mre prnunced; 4) Terminal grwth is f "feather duster" type; 5) Twig dieback and defliatin ccurs; and 6) On lder trees the bark n the trunk becmes cracked and splits pen. 12 AVOCADO GROWER Zinc deficiency is easily crrected, either by a fliage spray r sil applicatin. The fliage spray is usually applied in the spring after the new spring flush f leaves has fully expanded. This nrmally ccurs in June. The recmmended spray is ne (1) pund f zinc sulfate (36 percent metallic zinc) in 100 gallns f water. Aerial applicatin f zinc using a helicpter r fixed wing aircraft has prduced variable results. In sme rchards the zinc level in leaves did nt increase after an aerial applicatin. The reasn fr this is nt knwn. A leaf analysis is recmmended yearly t maintain a check n the efficiency f the zinc treatment. Sil applicatin with zinc sulfate (36 percent metallic zinc) may be used with gd results n acid-type sils. The sil applicatin is suggested fr rchards where spray rigs d nt have access, such as crwded rchards and/ r steep land. The sil treatment gives a slwer respnse than a fliage spray, but prduces a lnger effect. Sil applicatin will be effective frm 3 t 6 years, while spraying must be dne annually. Effectiveness f zinc placed n the sil depends n the sil type, sil ph, and rate f applicatin. The mre carse and pen the sil, the quicker the respnse. On clay-type sils, the perid befre any crrectin is nticed will be abut ne year after applicatin. Applying zinc t alkaline sils is seldm effective. Sil applicatin f zinc can be dne at any time during the year. Fall is usually best, hwever, because winter rains take the zinc int the surface sil. Chart 4 prvides a table f dsages fr varius aged trees: -----Chart Age Years Dsage Per Tree (punds) 1 Zinc sulfate (36% zn) 2 Zinc sulfate (36% zn) 3 Zinc sulfate (36% zn) 4 Zinc sulfate (36% zn) 6 Zinc sulfate (36 % zn) 7 Zinc sulfate (36 % zn) A recmmended methd f applicatin is t place the material in a band abut tw feet wide at the dripline f large trees. Fr smaller trees use a prprtinately narrwer size band. Zinc chelate materials are effective as fa sil treatment. Ecnmics will determine whether zinc chelate r zinc sulfate will be used. Usually the sulfate is less expensive. Avcad trees supplied with sufficient zinc remain in a healthy cnditin. Irn Irn deficiency des nt ccur in the sil series where avcads are usually grwn in San Dieg Cunty. Deficiencies ccur n sils that are highly calcareus. In San Dieg Cunty the tw sils series that wuld be detrimental t avcads are Altamnt clay and Diabl clay. Knwledgeable grwers will never plant avcads in these sils because f the high clay cntent and the large amunt f calcium carbnate (limestne) present in the sil prfile. Symptms f irn deficiency appear n the leaves, and in several cases, defliatin and twig die-back ccur. Leaf symptms shw a pale green t yellw clr between the veins and veinlets. Veins remain green. As the deficiency increases, the area between the veins becmes a yellw r white and the veins lse their green clr. Leaves will be smaller, cmpletely chlrtic and shw marginal and tip burn in severe cases. Cntrl r crrectins f this deficiency is nt always pssible. High limestne in the sil limits the utilizatin f irn by the plant. West Indian type rtstcks are mst tlerant t calcareus sil. Mexican and Guatemalan rtstcks are nt t tlerant t high lime sils. Irn chelate materials have given variable results. Treatment is expensive. An applicatin f 1/4 t 1/ 2 pund irn chelate per mature tree in Mayr June is suggested. This treatment shuld be dne annually. Liquid Fertilizer Liquid fertilizers are nt new. They have been used n many crps- ranges, flwers, nurseries, strawberries, vegetables--fr many Cntinued n page 15

4 Cntinued frm page 13 years. When it was cnvenient, avcad grwers used liquids, but n a limited scale. Since many avcad rchards must use Clrad River water, irrigatin systems wuld becme clgged with a precipitate caused by the interactin f the high calcium in the water with the phsphrus cntaining fertilizer when it was injected int the irrigatin system. Tday, the suppliers f liquid fertilizers have frmulated mixed fertilizers t cunteract the high calcium in the irrigatin water which prevents the precipitate frm frming. Experience with fertilizing thrugh an irrigatin system has shwn that less fertilizer is required since the material is taken directly int the rt zne and the tree is able t btain the necessary nutrients easily. Fertilizing thrugh an irrigatin system reduces the lss f sme types f fertilizer due t vlatilizatin. "Fertigatin" reduces labr csts because rchard wrkers are n lnger required t spend many hurs spreading material by hand t thusands f trees. There are a few questins regarding the use f any type f fertilizer--wet r dry--that shuld be asked: 1. What des the avcad tree require in nutrient elements? The avcad tree needs mst nutrient elements. Hwever, many f them are btained frm the sil and water. Sme elements are deficient in bth the sil and water. The nutrients that must be added t the sil fr prper tree grwth are nitrgen, phsphrus, ptassium and zinc. These must be applied annually. All ther nutrients appear t be adequately supplied by the sil and water. 2. Hw des a grwer knw what the avcad tree requires? Leaf analysis is the best guide t fertilizing avcad trees. A leaf sample taken in the fall f the year will prvide the infrmatin necessary t plan an effective fertilizaun prgram. Refer t the fllwing discussin n "Leaf AnalYSis." Cntinued n page 66 Saturday, January 12, :00 PM t 6:00 PM In the Falicita Rm Escndid Mtr Htal 2500 S. Escndid Blvd. Escndid, CA Cmpany representatives will be available t answer yur questins and present new prducts and fertilizer prgrams. Basic Fertilizer Chevrn Unin/Cllier Swift WGMINrsk Hydr Prills H.J. Baker Liquid Fertilizer Equipment Clearwater Agri Pumps Ellenbe P.umps C"'\l\\",et\ fe"8s",,,en: 'Of a\\\ American Testihg Institute Minr Elements Leffingwell FMC Ciba Geigy Mnterey Chemical Miller Chemical McBride Distributrs/Kellgg Hme & Garden bth \J Grangett's Infrmatin Bth U.C. C-perative Extensin Specialists (Dn Gustafsn) Brught t yu by: GRANGETTO'S AGRICULTURAL SUPPLY CO. TWO LOCATIONS TO SERVE YOU: 1105 W. MISSION AVE LILAC RD. ESCONDIDO, CA VALLEY CENTER, CA (714) (714) AVOCADO GROWER 15,; Ai () ' ':;: en l;;, '0 II: c: ci z u

5 -ri Ci; u '-'. CfJ Q; "C a: c: ci z u "E U '-'..jl Q; a: c: PATHBUILDING I Paths n steep hillsides increase prductivity, reduce accidents & add prfits t every pick. We cut hillside paths anywhere in Califrnia! Fr details & cst estimate, call (805) r write: ElLTA U A Knll Drive, Ventura, CA Cnfused Abut Organics? Our cmplete line f rganic prducts prvides excellent alternatives t meet the specific needs f yur grve and yur wallet. PROCESSED POULTRY FERTILIZER Cmpsed f 100% Pultry Manure Excellent surce f: - Organic matter Nutrients: majr and minr - Humus Sil bacteria (sil balance Imprvement) Misture Labratry tested - free frm rt rt ORGANIC MULCH Cmpsed f wd shavings, sawdust, decmpsed hay and straw. Machine shredded fr unifrm particle size Excellent surce f: - Organic matter (bulk frm 81.5%) - Nutrients: majr and minr - Humus - SU Bacteria Misture: Its greater misture retentin allws Increased lateral mvement f su misture fr extended rt develpment Labratry tested If yu are cnfused abut which prduct will best meet yur grve's requirements, we will be happy t prvide cnsultatin. In many cases, the best results are btained by using a cmbinatin f the tw (5, 10, r 15% Pultry Fertilizer cmbined with the Organic Mulch). This enables yu t add the vlume f bulk mulch required fr misture retentin, with the prescribed level f nutrients required by yur trees, regardless f age. Why settle fr ne su cnditiner when yu can custm rder t meet yur grve's, specific needs? Call us tday, r send fr literature and price lists. Yu'll like ur prices as much as yu like ur prducts. SINCE AGUINAGA FERTILIZER CO. COMPLETE LINE OF ORGANIC PRODUCTS (714) u HARVARD, IRVINE, CA AVOCADO GROWER Cntinued frm page Which fertilizer is best, liquid r dry? C9st f the material, cst f applicatin, ease f applicatin, and the uptake f nutrients t prvide adequate nutritin are factrs t cnsider. A leaf analysis will give the answer t what elements, and hw much, are taken up by the plant. Csts f each material r mix shuld be cmpared. The nutrients used shuld be based upn the data btained in the leaf analysis. T find the cst per pund f nitrgen, use the fllwing frmula: Cst per tn x 100 = Cst per pund f elemental nitrgen Percent nitrgen x 2,000 punds Example: Urea, $200 per tn, 46 percent nitrgen $200 x 100 = 21 7C per pund f elemental nitrgen 46 x 2,000 Leaf Analysis Annual leaf analysis prvides an excellent technique t mnitr the level f nutrients in the plant. The usual analysis will include nitrgen, phsphrus, ptassium, calcium, magnesium and zinc. A mre cmplete analysis--including such elements as irn, cpper, manganese, brn--is nt usually necessary because these elements are nt lacking in the avcad plant. A cmplete leaf analysis culd be dne every five years just t keep track f hw the tree is picking up the nutrients. Spring cycle leaves taken frm the trees in the fall mnths (August 15 t Octber 15) are subjected t a chemical test in the labratry. The nitrgen percentage is the mst reliable figure, and that f which mst is knwn, in relatinship t prductin. The percent nitrgen level is satisfactry fr Fuertes, Hacns, and Zutans. Hass leaf nitrgen levels shuld read higher, percent. Summary Fertilizatin f avcads in San Dieg Cunty must be dne n a regular basis. All age trees shuld be fertilized either with dry r liquid materials. Scheduling applicatins will vary depending upn age f JANUARY 1980

6 trees, type f irrigatin system (drip, sprinklers), and material used. If drip irrigatin is used t irrigate the rchard, fertilizatin must begin in February and cntinue until Nvember 1. Fertilizers must be injected int the system n a weekly r twice-a-mnth basis. The amunt f material t use is utlined in the chart lcated in the nitrgen sectin. If a liquid mixed fertilizer cntaining nitrgen, phsphrus and ptassium is used, the slutin shuld be acidified enugh t cunteract the high calcium in the irrigatin water. This prevents a precipitate frm frming and clgging the system. The liquid fertilizer likewise will be applied weekly. Befre purchasing any fertilizer it is sund financial management t determine the cst f each prduct available. A cmparisn can be made, based n the cst f the material and what is actually needed by the plant. There is n need t pay fr elements that are already supplied t the trees. A leaf analysis made each fall will prvide a gd recrd f a fertilizer prgram. Labratry results will vary each year. If an analysis is dne faithfully each year, the value f leaf analysis is enhanced. It is really mre imprtant t establish trends in each f the elements ver the years than t have just ne reading within a span f years. Leaf analysis is an excellent tl and shuld be a part f each grwer's fertilizatin prgram. Fr many years grwers have used acid-residue type nitrgen fertilizers such as urea and ammnium nitrate. If a sil ph reading has nt been dne within the last tw t five years, it may be a gd idea t have the sil ph tted. If the ph drps belw ph six then sme type f liming shuld be dne. SWitching t calcium nitrate as a nitrgen surce is an effective way f crrecting the acid cnditin. limestne can be used if the ph is lw and a relatively quick respnse is necessary. Caref41 attentin t the fertilizer prgram will pay dividends in reduced use f fertilizer, lwer csts, prper sil cnditins, imprved tree health and increased yields. 6- BRIGHT BRANO SINCE /,; :r,,/ GROWERS PACKERS SHIPPER PROMPT PERSONAL SERVICE Call Usl BRIGHT AVOCADO COMPANY New LatJn: Satlcy E cndld (806) (714) (Frqmil... C.IlCOIIect) (714) Del Di Highway, Escndid. Ca AVOCADO PACKING & MARKETI e F, (3... LUPrthat's there when yu need it Mdern prductin agriculture makes every minute cunt. That's why pea annual financing measures up with tp grwers. With a line f credit established, purchasing decisins mve ahead n yur timetable; yu bargain with cash and eliminate paperwrk ver each transactin. Fast, efficient, dependable... that's PCA mney pwer fr mdern agriculture. SOUTHWEST CALIFORNIA PCA SAN LUIS OBISPO PCA Escndid (714) S8n Luis Obisp (805) VENTURAPCA Ventura (805) ()." Jl Gi "t:i cr: " z JANUARY 1980