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Odorless and tasteless? Not necessarily! It turns out that some find the willow plant tasty and nutritious, and if that’s not enough, it fulfills a central role in a breakthrough, Israeli-Jordan research study dealing with the challenge of wastewater discharged into open landscapes. And how is Ramat Hanadiv related to all this?
Do you remember the role played by the willow in the four species? Yes, it’s the one that’s considered to be ‘lacking smell and taste’ and it appears in the Midrash as representing a person who does not learn Torah or fulfill mitzvot, i.e. does not contribute to society. Well, it turns out that this is true no more. A unique study being conducted simultaneously at Ramat Hanadiv and in Jordan sheds new light on this plant’s qualities. The study has found that the willow is a biological filter for sewage and can be used as a pasture and forage species, and that it is economical and nutritious. If that’s not enough, it turns out that sewage actually improves its nutritional value. The willow and the treated wastewater improve each other’s value; here we have mutual responsibility.
To understand the importance and contribution of the study for agriculture and for open landscapes, we met with Hussein Muklada, a water engineer from the Volcani Center, who has coordinated this unique study at Ramat Hanadiv during the last five years. During the meeting we discovered a fascinating study that connects nature, agriculture and humans.
Firstly, we would like to understand, how is all this connected to Ramat Hanadiv?
“In recent years at Ramat Hanadiv, a wastewater purification system has been operating to purify wastewater to irrigate a 0.5 ha plot in the Nature Park. The plot included local vegetation comprising green olive tree, mastic tree, spiny broom, prickly burnet and seasonal herbaceous vegetation. With time, due to the combination of rain and purified water saturated with organic material, the plot began to suffer from excess water during the winter. This situation led to a lack of oxygen and excessive salinity of the water. These conditions made it difficult for the local vegetation to survive and led to the tree deaths. The area became a swamp that invited mosquitoes and flies. Invasive plants began to establish in the plot and the local vegetation began to disappear.”
And how is a small plot at Ramat Hanadiv connected to collaboration with Jordan?
“In recent years, with the support of the US Foreign Ministry, sewage treatment systems were established in Jordan, but just like at Ramat Hanadiv, an adequate solution for using the purified water was not found.
Within the framework of the MERC programme led by the US Foreign Ministry, to encourage scientific collaboration between Israel and its neighbouring countries, the people at the Volcani Center searched for a subject suitable for such collaboration. Thus was born the study that has already been running for five years, in Israel and in Jordan, led by researchers from Ramat Hanadiv and from the Volcani Center. The study, which is financed by the US Foreign Ministry, found that the willow tree, common in both countries, can be used as a biological filter for purified water. It was also found that the willow populations have different abilities to adapt to low-quality water. This rapidly growing plant is found on river banks and near streams. Besides its high resistance to irrigation with wastewater, and since it is considered to be an attractive food for small ruminants and cows, we were also asked to examine the effect of irrigation on its nutritional value. It turns out that irrigation with treated wastewater raises its nutritional value and increases its vegetative production (biomass). The willow tree can also be preserved as silage for animals during the fall.”
In comparison to alfalfa, which is considered to be the best forage food for animals, containing 15% protein, the willow leaves were found to contain 20% protein.
And you reached these conclusions from the small plot at Ramat Hanadiv?
“Ramat Hanadiv served as an ideal platform for the study since it met all the requirements – a natural plot irrigated with treated wastewater and a herd of goats grazing on site. Thus we were able to simultaneously examine the resistance of willow to treated wastewater and the nutritional quality of willow for the animals. In the first stage 300 willow trees were planted on half of the plot area. The growth rate was very rapid and we understood that the plant does well with this water.”
Is the irrigated plant suitable as food for animals?
“To examine this issue we fed willow to goats from the herd at Ramat Hanadiv in a controlled way and we ran blood tests before and after feeding.
The findings indicate that rather than harming their health, this food has great nutritional value for them. In comparison to alfalfa, which is considered to be the best forage food for animals, containing 15% protein, the willow leaves were found to contain 20% protein. Together with the stems, the protein content was 14%, similar to alfalfa. But we were not satisfied with this; it was important to us to examine what proportion of the nutrients in the wastewater-irrigated soil reaches the leaves. For example, we discovered that the aluminium that is often found in the soil does not reach the leaves. Also with respect to copper, which may harm animals at certain levels, it was found that it accumulates mainly in the roots and the amount that reaches the leaves is within the acceptable, harmless range.”
In the photo: on the left, goats in the goat pen at Ramat Hanadiv after a day of grazing and two additional kg fresh willow per goat; on the right, the same trough two hours later.
And what are the health benefits of the plant for animals?
“Willow has secondary substances with medicinal qualities – anti-inflammatory substances, and those that reduce temperature and pain. We tested whether irrigation with treated wastewater preserves these substances. Tests of milk quality in the goat pen showed that the healthy substances stayed active even with irrigation by treated wastewater. In the milk of goats fed with willow we identified both anti-inflammatory effects and anti-bacterial effects. Inflammatory phenomena common at the end of the milking season disappeared, and the bacterial count of the milk of those same goats was found to be lower.”
And what about the study in Jordan? Are the results similar?
“Our colleagues grew the willow in harsher conditions, in the Al-Shobak region, south of Petra, at 1500 m altitude. Winter there is snowy and the soil is sandy and contains a lot of salt. Despite these conditions the willows grew amazingly. The collaboration led the Jordanians to come to us and learn about the study. We go to them, instruct them and learn much from them about silage.”
What are the future research directions?
“The study will continue to compare the state of the willows irrigated with wastewater to those irrigated with regular water. Moreover, now that we know that willows grow better with treated wastewater, which contains more salts than regular water, we have begun to develop the idea of growing willow forage irrigated with brackish water, which is abundant in the Negev and in the Arava. Dr. Josh Klein has shown that willows can indeed take root in brackish water. As in Jordan, we also have a forage crisis in arid regions, and if we’ll find that treated wastewater, which is abundant in Jordan, and brackish water, which is abundant in the Negev, can be used in these regions, we’ll be able to bring good news to the farmers of the Negev and the Arava.”
And in our little willow plot at Ramat Hanadiv, the problem of excess water has been solved and the invasive vegetation is disappearing.
Hussein Muklada is a research engineer at the Volcani Center and has collaborated with Ramat Hanadiv for the last 14 years. He coordinates research on the willows under the guidance of Dr. Yan Landau from the Volcani Center – Agricultural Research Organization and the director of research on the Israeli side, Dr. Yehoshua Klein from the Volcani Center – Agricultural Research Organization.
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