The last time Lebanese farmer Zakaria Farah visited his fields outside the southern town of Qlayaa was in January, but it was not to plant. With shelling heard in the distance, he swiftly pressed his hands into the soil to gather samples that could determine his family's farming future.

After bagging up the earth, Farah, 30, sent half a dozen samples to a laboratory at the American University of Beirut (AUB) to be tested for the residue of white phosphorus from Israeli shelling, hoping he'd learn whether he could plant his fields once hostilities end.

"I want to know what I'm feeding my son, what I'm feeding my wife, what I'm eating," he told Reuters in June.

"We're afraid for the future of our land. What can we eat? What can we drink?" Farah told Reuters he fears his fields have been poisoned by the Israeli military's use of white phosphorus since October when exchanges of fire erupted between Israel and Lebanese armed group Hezbollah in parallel with the Gaza war. He said there are dozens of farmers in south Lebanon as worried as he is.

According to the Lebanese National Council for Scientific Research, there have been 175 Israeli attacks on south Lebanon using white phosphorus since then, many of them sparking fires that have affected over 600 hectares (1,480 acres) of farmland.

White phosphorus munitions are not banned as a chemical weapon and can be used in war to make smoke screens, mark targets or burn buildings – but since they can cause serious burns and start fires, international conventions prohibit their use against military targets located among civilians.

Lebanon is a party to those international protocols, while Israel is not. In June, Human Rights Watch (HRW) said it had verified the use of white phosphorus in at least 17 municipalities in southern Lebanon since October, including five "where airburst munitions were unlawfully used over populated residential areas."

In response to questions from Reuters, the Israeli military said the "primary smoke shells" it used do not contain white phosphorus. It said smoke shells that do include white phosphorus can be used to create smokescreens, and that it "uses only lawful means of warfare."

According to a December report on Lebanon by the U.N. Development Programme (UNDP), white phosphorus is extremely poisonous and poses "ongoing and unpredictable hazards due to its prolonged and difficult-to-control burning, creating serious risks to human health, safety, and the environment." The agency said that soil quality in the conflict area of southern Lebanon had been affected by the spread of heavy metals and toxic compounds, with "white phosphorus usage further reducing fertility and increasing soil acidity."

Soil science

Farah and other farmers estimate they have already lost up to $7,000 each in potential income, as continuing bombardment has made it too risky for them to plant or harvest the usual seasons of wheat, tobacco, lentils and other greens.

Oday Abou Sari, a farmer from the southern town of Dhayra, said white phosphorus had also burned hay he had gathered for livestock and even plastic irrigation pipes across his fields.

"I have to start all over – but first, I need to know if it's safe for planting," said Abou Sari.

To find out if the white phosphorus has left a lasting impact on their soil, farmers are digging in – literally – and sending samples to Dr. Rami Zurayk, a soil chemist at AUB.

Zurayk developed a research protocol to collect and examine the samples. First, soil is gathered at various distances from the impact site, including a control sample from 500 meters away – which would not have been directly affected by the strike.

Once in his lab, the soil is sifted, mixed with acid and exposed to high heat and pressure. A solution is added to show the concentration of phosphorus, with the intensity of color in the result matching the concentration of the phosphorus. The sample is then compared to the control, which sets the benchmark of naturally occurring phosphorus in the soil.

"What we're looking for is what happens to the soils and to the plants in locations that have received white phosphorus bombing. Does the phosphorus remain? In what concentrations? Does it disappear?" Zurayk told Reuters.

His assistant, doctoral student Leen Dirani, told Reuters she had thus far tested samples from four towns this way – but they need more samples to "obtain a conclusive outcome."

But the steady pace of Israeli shelling on southern Lebanon – particularly agricultural fields that Hezbollah is accused of using as cover – has made farmers unwilling to venture out to gather more samples. Some, like Abou Sari, have left Lebanon altogether. He is waiting out the war abroad and so for now is unable to obtain soil samples.

Others are documenting through video footage. Green Southerners, a collective of ecologists and nature lovers in Lebanon's south, have filmed several incidents of shelling showing the tell-tale signs of white phosphorous attacks: dozens of streams of white bursting out of a munition over farmlands.

The group's chairperson Hisham Younes told Reuters the attacks' "frightening density" amounts to ecocide – mass destruction of a natural environment by humans, deliberately or by negligence.

Given the possible impacts on soil, water reserves and even ancient trees, "we are talking about a profound injury to the natural system. The repercussions are multiplied," Younes said.

Lebanon's ministries of environment and agriculture are working with UNDP to determine the extent of those repercussions, and hope to use any documentation or lab results to stand up complaints to the United Nations.

"This is an act of ecocide, and we'll take it to the U.N. Security Council," Lebanese environment minister Nasser Yassin told Reuters.

In response to questions from Reuters, the Israeli military said the accusation of ecocide was "completely baseless."