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Stories from the valley

Water + Sunlight + Soil + Carbon = Food

Contributed by Dan Macon

My friend Jean Allender tells a wonderful story about her father’s fruit orchard in the 1950s and 1960s.  Her dad would hire a number of teenage boys each summer, starting them all out as irrigators.  After several weeks, he’d talk to them each individually and ask them what they understood their job to be.  According to Jean, most of the boys would say, “My job is moving pipe to irrigate the orchards.”  But every summer, there were a couple of boys who would answer, “My job is to keep the trees alive.”  Those boys became the permanent irrigation crew; the other kids were moved to other less vital jobs.

At its essence, the job we do as farmers and ranchers involves combining water, sunlight, soil and carbon to produce food and fiber.  The actual work involved, however, is not that simple.  Let me take one of these elements – water, which keeps our crops alive  – and describe the thought and work that goes into managing it on our ranch.

SheepWe use irrigation water to grow grass for our sheep.  Unlike watering your yard, irrigating any crop is a complex endeavor.  Our irrigation management begins with knowledge about our soils.  We need to know how much water our soil can hold, and how quickly the water will soak in.  This means that we need to know how much organic matter our soil has (and that we look for ways to increase organic matter, which acts like a sponge).  We also need to understand the proportion of sand, silt and clay – the three types of soil particles – present in our soils.  This way we can apply just the right amount of water at just the right time and for just the right duration – we don’t want run-off, but we don’t want to stress our pasture plants, either.

Secondly, we need to understand the water demands of our plants.  This demand varies from one day to the next – depending on temperature, humidity, growth phase of our plants, day length, and a variety of other factors.  And some of the water we apply never makes it to the plant – it evaporates into the atmosphere.  To monitor this ever-changing set of parameters, we check the California Irrigation Management Information System (CIMIS) website for real-time data about evapotranspiration (water that evaporates or is transpired by our plants) for our area.

We then combine this knowledge, along with readings from moisture sensors we’ve installed in our pastures, to schedule our irrigation.  We know how much water our sprinklers will apply, and we time our sprinkler moves based on current demand from our plants.  In the cooler late spring and early fall months, we don’t need to apply as much water (so we move sprinklers more frequently).  In August, however, our plants need plenty of water.

Taking a step back, irrigating pasture is part of a bigger and even more complicated system for us.  From late October through late April, we graze on unirrigated rangelands.  Our sheep help us improve the health of these lands – they eat yellow starthistle, medusahead barley, and other invasive weeds.  They help us manage the fuel-load in our community, reducing the threat of wildfire in summertime.  Our grazing system improves wildlife habitat and protects watersheds.  But we need green grass in the summer months, too – when our annual rangelands have turned to California gold (or brown, depending on one’s perspective).  In some ways, our summer irrigated pastures allow us to use our sheep for ecological improvement during the rest of the year – we simply couldn’t raise sheep without green grass in the summer months.

Which brings me to the ongoing debate about agricultural water use in California.  Based on the discussions I’ve read in my newspaper and heard on the radio, many of my suburban and urban neighbors are only now realizing that California is in the fourth year of one of the most severe droughts in modern times.  I’ve also seen much discussion about which crops use the most water, and about overall agricultural water use.  Farms and ranches use about 40 percent of the water in California (or 80 percent of the “developed” water – water used for human purposes).  Some crops – especially almonds and alfalfa – come in for special criticism.  What’s lost, at least from my perspective, is the understanding that ALL food production – EVERYWHERE – requires water.  Farmers and ranchers have to make complex decisions about crops – based on soil quality, water availability, markets, and other factors.  From my perspective, the discussion needs to begin with the understanding that all of us who eat are the end users of agricultural water.