How Intensive Agriculture and Olive Cultivation Impact Soil Health

The 27^th Conference of the Parties to the United Nations Framework Convention on Climate Change – COP27 – is just around the cor­ner, kick­ing off on November 8^th 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.

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.

While this type of agri­cul­ture has allowed the global pop­u­la­tion to grow expo­nen­tially from an esti­mated 1 bil­lion peo­ple in the mid-19^th 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.

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.

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.

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.