Donald L. Suarez


I'm Donald Suarez. Director of the US Salinity Laboratory, ARS, USDA.

I got a PhD in Geochemistry from Penn State University in 1974. And I've worked ever since
then here for the Department of Agriculture at the US Salinity Laboratory as a researcher. 

What we are looking at is using alternative water sources for irrigation. With scarcity of fresh
water supplies in the Western United States we know that to sustain agriculture and irrigation we
are going to indeed to use lower quality waters. So we are looking at agricultural drainage waters, 
recycled for irrigation. We are looking at treated municipal waste waters for irrigation. And the
challenges are related to salinity, organic matter in the soil, differences in pH so there's a lot of
criteria for water that are different then typical water sources for irrigation. 

The existing guidelines were designed in an era of abundant  water supplies and the idea being
that we wanted to use waters of only the highest quality that would avoid any problems in terms
of plant production or in terms of adverse effects on the soils but that luxury of being so
conservative in terms of which waters we use doesn't exist any more and these marginal quality
waters we can use them in many instances so we need to understand when we can use them and
when we can't use them.

These water quality criteria can't be just uniformly applied. There's many factors that enter in to
this.  For example, with scarce water supplies it's really important that we maximize the
infiltration point of our rain. These synthetics waters made up with different levels of sodium and
pH are in those barrels. We do one irrigation cycle assuming a rain event we let it dry then we do
an irrigation event. We look at the interaction of the two. 

In this experiment we're looking at irrigating grasses that are used in the Western United States
for landscaping purposes. We're looking at the effect of iron composition and we're looking at the
affects of salinity on growth response. 

Now for turf it's a little bit different than crop production we don't necessarily have to produce a
lot of biomass  we just have to keep it healthy looking so appearances are important and the
objective is to minimize the amount of water we apply.

Landscaping is the first place that we can conserve water out here in the west. We have a variety
of water compositions here this experiment going from what we would call top water all the way
up to one third sea water in terms of salt composition. We do have a lot of brackish waters in the
western US. The idea is that for landscaping we should avoiding using our high quality fresh
waters. These have to be saved for the municipal sector for drinking purposes after the urban
sector has used the water there is still water available that can then be used by the agricultural or
landscaping environment. We really get two uses out of that water.

This work on water reuse is rather complex it ranges from the response of crops to these waters
and crop response is not just to the salinity so we are looking at the impacts of iron composition,
pH on plant production we also with these waters often have to have potentially toxic trace
elements present. Of particular concern is boron. Boron is present in agricultural drainage waters
and also municipal waste waters and its potentially toxic to plant growth we try to develop water
criteria based on maintaining good physical properties of the soil and so this also involves
computer modeling because we can't run the experiments for twenty-thirty years. We can't wait
around to see what those response are going to be. We have to use the limited data we have
develop computer models, we validate them on short term experiments and then we use them to
make simulations of what the long term outcomes are likely to be. 

We have excellent cooperation here in not only as an interdisciplinary team within the lab but
also with the University of California, Riverside and also we have a large number of visiting
foreign scientists that come through our lab and assist us in projects that are of mutual interest.
The problems we face are the same problems that irrigated agriculture faces in all the arid and
semi-arid regions of the world.

What's really unique when you travel to some other countries in arid zones is that they have even
less fresh water then we do and so places in the Middle East and in North Africa it's a unique
environment really to study existing systems that are being utilized with very high salinities
trying to grow crops that we ordinarily would not attempt to grow with those waters such as
vegetable crops. They have developed varieties that are more salt tolerant than varieties that we
have.  The challenge will be for us will be to integrate those into our production systems and 
potentially modify them to our climates and soils. 

The models that we've developed on water quality criteria and plant responses to salinity have
been well received throughout the world and are being, I think, adopted. We have a leadership
position with regards to setting the criteria for irrigation. Looking at long term affects in terms of
plant production and soil physical and chemical properties. 

And it's a real honor for me to receive this award from the agency.