How Intensive Agriculture and Olive Cultivation Impact Soil Health

While intensive agriculture degrades soil health in seasonal crops, the same cannot be conclusively said about olives.

Bakersfield, California
Oct. 27, 2022
By Daniel Dawson
Bakersfield, California

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The 27th Conference of the Parties to the United Nations Framework Convention on Climate Change – COP27 – is just around the cor­ner, kick­ing off on November 8th in Egypt’s sunny resort town of Sharm El-Sheikh.

Among the even­t’s many focuses will be agri­cul­ture’s role in cli­mate change, to which an entire day has been ded­i­cated.

There are not many stud­ies com­par­ing the change in soil fer­til­ity between tra­di­tional or inten­sive olive groves.- Roberto García Ruiz, agri­cul­tural researchers, University of Jaén

And with good rea­son. The International Panel on Climate Change esti­mates that agri­cul­ture is respon­si­ble for 10 to 12 per­cent of global emis­sions and one-quar­ter of green­house gas emis­sions.

However, not all agri­cul­ture is cre­ated equal. The lion’s share of these emis­sions is asso­ci­ated with chem­i­cal and indus­trial agri­cul­ture and its immense sup­ply chain fueled by oil and gas.

See Also:Hot Weather Weakens Plant Immune System, Study Finds

While this type of agri­cul­ture has allowed the global pop­u­la­tion to grow expo­nen­tially from an esti­mated 1 bil­lion peo­ple in the mid-19th cen­tury to nearly 8 bil­lion today, the spoils have not been shared equi­tably, and the costs have been immense.

Chemical agri­cul­ture can be traced back to 1840 when Baron Justus von Liebig, a German chemist, pub­lished a mono­graph enti­tled Chemistry in Its Application to Agriculture, in which he shifted the pre­vail­ing par­a­digm of soil biol­ogy to soil chem­istry.

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His dis­cov­ery allowed for the advent of indus­trial agri­cul­ture about 100 years later when the nec­es­sary ingre­di­ents were stock­piled in abun­dance after the end of World War II.

Plants require 17 essen­tial ele­ments to grow, but von Liebig iden­ti­fied the three most impor­tant ones – nitro­gen, phos­pho­rous and potas­sium.

While all three of these essen­tial nutri­ents and the other 14 are found nat­u­rally in the soil and pro­duced through bio­log­i­cal processes, their con­cen­tra­tion and pres­ence is the lim­it­ing fac­tor of soil fer­til­ity.

Applying NPK fer­til­iz­ers (the ini­tials of the three main ele­ments on the peri­odic table) raised these lim­its but had many unin­tended, albeit fore­seen, con­se­quences. The repet­i­tive appli­ca­tion of these fer­til­iz­ers meant crops could be grown on the same land year after year. However, the ecosys­tem that nat­u­rally sup­ported life was degraded.

Intensive agri­cul­ture elim­i­nated the pre­vi­ously exist­ing sym­bio­sis between plant roots and soil microbes. Combined with the impacts of cli­mate change, this imbal­ance has resulted in a loss of 25 per­cent of the global insect pop­u­la­tion since 1990.

This loss of bio­di­ver­sity, com­bined with the unnat­u­rally dense amount of nutri­ents in the NPK-fer­til­ized crops, resulted in the rise of pests.

The U.N. Food and Agricultural Organization esti­mates that 40 per­cent of global crop pro­duc­tion – val­ued at about $290 bil­lion – is now lost to pests, with the prob­lem expected to become 10 to 25 per­cent worse as a result of cli­mate change.

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Without nat­ural preda­tors to main­tain a bal­ance, pest species have become more per­va­sive and eco­nom­i­cally dam­ag­ing, result­ing in the reg­u­lar deploy­ment of chem­i­cal pes­ti­cides.

Those pes­ti­cides fur­ther degraded soil health, ren­der­ing it unin­hab­it­able with­out the con­tin­ued use of NPK fer­til­iz­ers, essen­tially unlearn­ing 14,500 years of shared knowl­edge and expe­ri­ence in the space of 180 years.

The NPK men­tal­ity,” as von Liebig’s dis­cov­ery became deri­sively known among its crit­ics, overly sim­pli­fied soil fer­til­i­ty’s com­plex sys­tem biol­ogy.

Now some experts in the world of high-den­sity (inten­sive) and super-high-den­sity (super-inten­sive) olive groves are con­flicted over the impact that sys­tem­atic olive tree cul­ti­va­tion has on the soil.

One skep­tic said part of the uncer­tainty is the lack of stud­ies on soil health in high-den­sity and super-high-den­sity groves.

There are not many stud­ies com­par­ing the change in soil fer­til­ity between tra­di­tional or inten­sive olive groves,” Roberto García Ruiz, an agri­cul­tural researcher at the University of Jaén spe­cial­iz­ing in olive cul­ti­va­tion, told Olive Oil Times.

When I try to work in super-inten­sive groves to do this kind of com­par­i­son, [inten­sive olive grove own­ers] do not want any­one to take soil sam­ples or do any kind of analy­sis,” he added. I don’t know if it’s bet­ter or worse because I don’t have that infor­ma­tion.”

Unlike sea­sonal crops, which are most asso­ci­ated with indus­trial agri­cul­ture, olives are a per­ma­nent crop. As a result, olive trees have a fun­da­men­tally dif­fer­ent rela­tion­ship with the soil.

Ruiz sus­pects that the per­ma­nent root struc­tures pre­serve soil bio­di­ver­sity and pre­vent ero­sion in ways that the roots of inten­sive sea­sonal crops do not.

He added that many high-den­sity and super-high-den­sity grow­ers – by some esti­mates up to 90 per­cent – try to grow spon­ta­neous nat­ural veg­e­ta­tion between the rows of their olive trees to vary­ing degrees of suc­cess.

See Also:Researchers Find a Way to Expedite Photosynthesis

In a nat­ural ecosys­tem, dif­fer­ent plants fix dif­fer­ent nutri­ents into the soil. For exam­ple, legumes nat­u­rally fix nitro­gen, which is why many farm­ers alter­nate between wheat or corn and soy­beans. However, Ruiz said legu­mi­nous plants do not grow well in high-den­sity and super-high-den­sity groves.

Additionally, the vast major­ity of high-den­sity and super-high-den­sity groves are fer­ti­gated, a com­bi­na­tion of irri­ga­tion with a dis­solved NPK fer­til­izer.

As a result, these groves have the same prob­lem as inten­sive sea­sonal crops, with a nutri­ent-dense com­po­si­tion that attracts pests and usu­ally requires pes­ti­cides to keep them at bay.

The envi­ron­men­tal impact will depend on the type of pes­ti­cide used, but chem­i­cal pes­ti­cides will have the same effects on the soil as they do in inten­sive sea­sonal crops.

However, Juan Vilar, a strate­gic con­sul­tant who oper­ates his own tra­di­tional and high-den­sity olive groves, argued that soil health in olive groves is related to cul­ti­va­tion meth­ods other than den­sity.

He agrees with Ruiz that spon­ta­neous nat­ural veg­e­ta­tion in most high-den­sity and super-high-den­sity groves cer­tainly helps main­tain and pro­mote soil fer­til­ity.

When work­ing with plant cover, the fer­til­ity of the soil is main­tained and grad­u­ally enriched because it reg­u­larly adds organic mat­ter,” he told Olive Oil Times.

Vilar acknowl­edged that using chem­i­cal pes­ti­cides and her­bi­cides would also undoubt­edly impact soil health but argued this is not directly tied to the cul­ti­va­tion method.

The health of the soil depends on what fer­til­iz­ers and chem­i­cals are used to man­age the cover crops,” he said.

Depending on what prod­uct you use, if they are prod­ucts that are very rad­i­cal in their com­po­si­tion, the soil fer­til­ity can be affected,” Vilar added. But it does not depend on the mode if it is inten­sive, super-inten­sive or tra­di­tional, but rather on how the soil is treated.”

There is lit­tle argu­ment that high-den­sity and super-high-den­sity olive groves har­bor more bio­di­ver­sity than inten­sively cul­ti­vated sea­sonal crops.

However, some research has found that these olive groves neg­a­tively affect bio­di­ver­sity com­pared with tra­di­tional groves, which impacts soil health.

While some dis­pute these find­ings, both sides agree that more research must be done. In the mean­time, no one is sug­gest­ing that high-den­sity and super-high-den­sity groves do not have a place in the global olive cul­ti­va­tion port­fo­lio.

However, Ruiz said that ensur­ing they are as sus­tain­able as pos­si­ble means they must be located where water is avail­able for irri­ga­tion, a neces­sity for high-den­sity and super-high-den­sity olive groves high­lighted by the cur­rent his­toric drought fac­ing south­ern and west­ern Europe.

The soil pro­file is also essen­tial to con­sider, as ris­ing tem­per­a­tures fun­da­men­tally change how plants and soil inter­act.

It is quite clear that tak­ing the main cli­mate change sce­nario into account, the cul­ti­va­tion area in Andalusia [home to the vast major­ity of the world’s high-den­sity and super-high-den­sity groves] will have to move a lit­tle bit toward the east and the north,” Ruiz con­cluded.


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