Fact, fash­ion or fic­tion?

Keep­ing it sim­ple is al­ways best.

The Orchardist - - Orchard Management - By John Wil­ton

The in­dus­try must be flush with money at the mo­ment. Look­ing at the way land val­ues have sky­rock­eted and the com­plex, ex­pen­sive, untested grow­ing sys­tems be­ing adopted, sure gives this im­pres­sion.

In my younger days, I was in­volved in Jaycees and one of our mantras was “KISS – keep it sim­ple stupid”. In gen­eral, this rule still ap­plies. When it comes to grow­ing fruit trees, this prin­ci­ple cer­tainly ap­plies. The closer your train­ing sys­tem is to the tree’s nat­u­ral growth habit, the eas­ier it will be to es­tab­lish a prof­itable or­chard and the lower the cap­i­tal out­lay in­volved.

THE IN­TEN­SI­FI­CA­TION MYTH

In re­cent years we have seen tree plant­ing den­si­ties rise well above op­ti­mum plant­ing den­si­ties for our cli­matic con­di­tions and soil tree vigour po­ten­tial. Rel­a­tive to many parts of

the world where ap­ples are ma­jor crops we have a long grow­ing sea­son with rel­a­tively mild sum­mer tem­per­a­tures, so there are few days in our sum­mer with tem­per­a­tures high enough to shut down ef­fi­cient leaf pho­to­syn­the­sis. Ap­ple leaf pho­to­syn­the­sis ef­fi­ciency tends to fall off rapidly once tem­per­a­tures rise much above 28°C. In con­ti­nen­tal cli­mates, such as Wash­ing­ton or warmer lower lat­i­tude grow­ing ar­eas, such as the cen­tral val­ley in Chile or South Africa, tree growth and fruit siz­ing shuts down for the hottest part of the grow­ing sea­son.

With our longer, ef­fec­tive grow­ing sea­son here, tree vigour is gen­er­ally stronger than found in most ap­ple grow­ing ar­eas around the world. Our high lev­els of rel­a­tively un­in­ter­rupted pho­to­syn­the­sis means that young trees have both good vigour and the ca­pa­bil­ity of siz­ing sig­nif­i­cant crop loads. Usu­ally, these are at crop­ping lev­els well above those quoted in pub­lished sci­en­tific lit­er­a­ture from else­where in the world.

The ob­jec­tive of ob­tain­ing early yields is of­ten quoted as the driver for in­ten­sive plant­ing. This be­ing so, one would ex­pect to see sig­nif­i­cant pro­duc­tion as early as the year of the plant­ing and cer­tainly in the next year. This is the case in many north­ern Euro­pean plant­ings. The nurs­ery­man there grows a big, well-feath­ered tree ca­pa­ble of fruit­ing in the year of plant­ing and at the den­si­ties they plant these big trees at, they would be in big trou­ble with ex­cess vigour if they did not crop them as soon as pos­si­ble.

Yet, when I look at some of our higher den­sity plant­ings, crop­ping will be sev­eral years away be­cause most of the po­ten­tial fruit­ing wood for these early crops is promptly pruned off to make the tree grow and con­form to the pro­posed in­ten­sive tree-train­ing sys­tem.

Ear­lier this year we had a staff con­fer­ence out of Hawke’s Bay where we were shown dif­fer­ent plant­ing sys­tems, most more in­ten­sive than the Hawke’s Bay norm. When the ques­tion was asked, why the trees were not be­ing cropped in the first cou­ple of years, we were told crop­ping them would hin­der tree de­vel­op­ment. What is the point of plant­ing high tree

“Trees with ad­e­quate room to ac­com­mo­date their vigour will set­tle down to reg­u­lar crop­ping with­out huge ma­nip­u­la­tion.”

den­si­ties if you are not go­ing to crop them as soon as pos­si­ble to start get­ting a re­turn on the ex­tra cap­i­tal out­lay re­quired for plant­ing trees at high den­sity?

Some years ago, I ran re­gres­sion anal­y­sis on young tree yields against tree de­vel­op­ment ex­pressed as per­cent­age in­crease in trunk cross sec­tional area us­ing data pre­sented by Dr John Palmer at fruit grower sem­i­nars. I can­not re­mem­ber the ex­act R² re­sult of this anal­y­sis, ex­cept that it was well un­der 0.1, so crop load had a very mi­nor ef­fect on tree growth. Crop load is there­fore, not the main cause of poor young tree per­for­mance. The no­tion that you should not crop young trees be­cause it will in­hibit their de­vel­op­ment is ob­vi­ously fic­tion.

As well as crop load, there are many fac­tors that limit young tree growth. These in­clude the three W’s; wa­ter, weeds and wind, in­hos­pitable soils for root de­vel­op­ment, ex­ces­sive blos­som lev­els and too many grow­ing points caused by in­suf­fi­cient prun­ing out of lat­er­als along the leader, as well as lat­er­als bunched to­gether and chok­ing the leader. We have found that the tree is quite ca­pa­ble of car­ry­ing the crop that re­mains on a young tree af­ter a heavy hit with an ag­gres­sive post­blos­som thin­ner and at the den­si­ties we plant at to­day make sat­is­fac­tory canopy de­vel­op­ment with that crop level.

Op­ti­mum plant­ing den­si­ties de­pend on soil qual­ity, root­stock, scion vigour and tree canopy form. Crop load is your best vigour control agent. Be­cause it usu­ally takes two to three grow­ing sea­sons for a branch to carry suf­fi­cient crop to achieve a good vigour/crop bal­ance, trees need to be far enough apart to al­low at least two years of an­nual shoot ex­ten­sion growth be­fore run­ning into canopy den­sity problems in the next tree.

MA­TURE OR­CHARD PER­FOR­MANCE

One of the problems with or­chard sys­tem tri­als is that in many the trial is ter­mi­nated af­ter five or six years, so there’s not a lot of data about on how the var­i­ous plant­ing sys­tems per­form af­ter full canopy is reached. Most or­chards do not cover es­tab­lish­ment costs un­til at least four to eight years af­ter plant­ing, de­pend­ing on es­tab­lish­ment costs and tree growth in the es­tab­lish­ment pe­riod. Most data in­di­cates that breakeven on di­rect op­er­at­ing costs will oc­cur sooner, of­ten three to five years af­ter plant­ing. Canopy de­vel­op­ment and yields by this stage have barely reached half way to­wards full po­ten­tial when breakeven on di­rect op­er­at­ing costs oc­curs.

The real suc­cess of the plant­ing is de­ter­mined by the full canopy yield and qual­ity per­for­mance achieved and how long this level of pro­duc­tion can be main­tained. The longer you can main­tain high yield and qual­ity in an or­chard plant­ing, the bet­ter the in­ter­nal rate of re­turn will be. Pro­vided the va­ri­ety is not su­perceded and the or­chard is main­tained well and does not suf­fer any ma­jor dis­ease problems, a pro­duc­tive life of 20 years or more should be pos­si­ble.

We have an ex­ten­sive data­base on or­chard block per­for­mance cover­ing a num­ber of years. I in­ves­ti­gated ma­ture or­chard per­for­mance for Scifresh over the 2016 and 2017 har­vests and the 2017 and 2018 har­vests. In gen­er­at­ing the data, two con­sec­u­tive years of pro­duc­tion was com­bined to re­move any bi­en­nial-bear­ing in­flu­ence. Re­gres­sion anal­y­sis of yield and profit against tree den­sity was car­ried out. The dataset for the 2016 and 2017 sea­sons was more com­plete than that of the 2017 and 2018 sea­sons so the R² for the 2016 and 2017 sea­sons was bet­ter than for the 2017 and 2018 sea­sons.

The ta­ble be­low shows the R² re­sults. The trend lines all showed both profit and yield were max­imised at around 1500 trees per hectare and were sim­i­lar for both sets of data.

The con­clu­sions we can draw from the data is that in the real com­mer­cial world dif­fer­ences in tree den­sity in­flu­ences only around 15 per­cent of the huge range in or­chard yields and con­trary to pop­u­lar be­lief, and most short term sys­tems trial data op­ti­mum plant­ing den­si­ties are lower than the 2500 to 3000 trees per hectare usu­ally rec­om­mended.

Fig 2. This Scilate block is on the same root­stock as the block in Fig 1 but planted at 2381 trees/ha. Cu­mu­la­tive packed yield by the third leaf was only 3.99T/ha, partly be­cause of lower than op­ti­mum crops in years two and three and as a re­sult, poor ex­port fruit re­cov­ery in the third leaf. Or­chard man­age­ment rather than plant­ing den­sity de­ter­mines young or­chard per­for­mance.

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