Drought and the Importance of Soil Cover

 

Drought and the Importance of Soil Cover

Hugh Lovel

 

It’s dire days when so many Australian farmers along the Murray/Darling have burned up the carbon in their soils and turned their paddocks into salt flats resembling some of the dry salt pans of Arizona. It is puzzling, having viewed Channel 9’s special (28/5/2006) on salinity in the Murray/Darling, that our government has been trying to get more fresh water to run straight off down the rivers by ripping out the willows, as well as attempting de-salination by mining salt from wells in the basin—at enormous expense I might add. Does anyone have any idea how much salt is down there? It would make much more sense to give farmers incentives to re-carbonize their soils and phase out salt fertilizers, and to keep as much fresh water spread out on top of the land and the upper water table—that is our branches, creeks and rivers—as possible. Any sailor or swimmer—and quite a few scientists—know that salt water is heavier than fresh water, so that if you keep fresh water on top of your paddocks and in your upper water table, the salt water won’t rise. But what has been going on so far instead of re-humification of soils and slowing down the run-off is the formation of barren salt flats that sit there reflecting the sun almost like mirrors, driving the clouds away. How could our government and our peak scientific body get it so wrong? Where are the holistic scientists, the people with a comprehensive overview that connect the dots between the thinking going on inside little boxes? Can’t we find a few that will consent to come on board as consultants from time to time? I’m not asking for the job myself and wouldn’t take it, as I have other things to do, but I can think of three or four talented folks that were featured in the Channel 9 special that I’d like to see working on this one.

Well, the Murray/Darling story is bad enough, but in a great many, many other places in Australia that are less flat and less vulnerable to salination, farmers are ‘conserving soil moisture’ by cultivating their fields absolutely bare over long periods of time and creating a crumb or dust mulch known as a ‘dry fallow’ where 5 or 6 cm. down the moisture is sealed in.

Of course, there is no question about it, evaporation ceases and the moisture—what little of it there is these days—is conserved. But I believe there is a fundamental flaw in this strategy that stems from compartmentalizing science. Rarely is a soil scientist a physicist or a meteorologist, though he may, to some degree, be a chemist or a microbiologist. But then too, there wouldn’t be many physicists, let alone meteorologists, who know as much as an aboriginal bushman or a Hopi Indian about making rain. I contend that this so-called scientifically proven practice of ‘dry fallowing’ not only is conserving the moisture in the soil—it’s conserving it in the atmosphere as well so that it no longer falls nearly as often as rain.

I often say that observation is the basis of intelligence. Check out this observation. In various summers I’ve driven the less travelled highways and back roads through the grazing and broadacre expanses of New Mexico, and a common phenomenon is for summer thunderstorms to criss-cross the landscape during the summer ‘rainy season’. The better part of this moisture falls from high clouds for a km. or so, but then evaporates back up into the clouds before it hits the ground. There’s actually quite a lot of moisture up there, but not much lands. What happens is inside the cloud the moisture is cool and thus ends up condensing until it falls as rain—but as it approaches the landscape where heat, radiating off the ground, creates the illusion (at a distance) of vast lakes of water, the falling rain warms up and evaporates back up into the clouds. This is ever so typical of areas where the soil is bare, soaking up the sun and giving it back off again as a writhing fabric of heat—palpable and parching to anyone afoot or on horseback. It’s clear why Mexican sombreros curve upward all around the brim—you wouldn’t want to trap any of that furnace blast under your hat. In fact, nowhere is it worse than on sealed roads where the nudity of the earth is enforced to the greatest extreme.

And yet, in this landscape are large properties following the precepts of what grazing guru, Alan Savory, has termed ‘Holistic Resource Management’ (HRM) where every effort is made to ensure that as much as possible of the surface is covered with some sort of vegetation or residue, some sort of carbonaceous organic matter, so that not so much as a square centimetre would be bare if that were possible. Vaulting the fence—from a ranch where there is hardly an uneaten blade and the heat is in your face—and landing on the other side in one of these properties where the soil is mostly covered with something, no matter if it is more brown than green, and the difference is breath giving, an enheartening relief. You can stand there and watch as one of these thunderstorms crosses the radiating landscape, spilling its rain towards, but often not onto, the ground. Almost at the fence line when it reaches an HRM property—some, even if not all, of the rain starts hitting the soil. And, maybe it is only a millimetre or two that the land is refreshed with in passing, before the sun regains the ascendancy and once again sets up the shimmering illusion of water—but the heat is less, once again, over the covered portions of the landscape.

If there has been rainfall on the bare land—and sometimes this occurs—there has been more on the covered land, giving mute testimony to carbon’s powerful affinity for hydrogen. Moreover, on the bare land it evaporates again straight away.

Meanwhile on the covered soil the moisture goes to ground and soaks in, again showing those with eyes to see how carbon clasps hydrogen to its bosom. There it is, greedily supped up by the various tiny organisms living under the protective shade of this nurturing habitat. And at night these myriad organisms are equally protected from heat loss and moistened with dew beneath their night-time covers, like an army of tiny joeys in a grand marsupial pouch.

Of course, the HRM ranch is a ‘lucky’ ranch where the rainfall is measurably greater, but that hardly explains the startling difference in results. Estimates have it that as much as half of the precipitation such a landscape absorbs is not rain, but dew. Though the rainfall is measured at somewhere between 6 and 20 inches annually and averages between 8 and 14 inches depending on location, in real terms this may mean those with a covered landscape are getting closer to 16 or 18 inches of quite usable precipitation per year. Interestingly, because the landscape is so thirsty so much of the time, very little moisture is lost. Instead much of it is conserved within the cell walls and skins or exoskeletons of living organisms, where limited drainage or evaporation occur. Moreover, when there is a good rain of 30 or 40 millimetres, the landscape is softer and there is seldom any runoff. It’s true, the ‘lucky’ ranch has a real problem filling up its dams, but neither have their wells run dry since they got their program working.

Of course, their stocking rate is somewhere around double that of neighbouring ranches with less perfect soil cover, which attests to how ‘lucky’ they are. Since it is a topic that is almost obsessive in these places, I’ve listened to the ‘luck’ stories in a few of the country cafes, and of course, kept my mouth shut; but you can tell that some are inclined to suspect there must be something to this business of making your own luck in this world.

I had the good fortune to visit the YLAD broadacre farm of Bill and Rhonda Daly at Young, NSW late this last November or early December ’07. The small grain crops in the region were either harvested or awaiting harvest. I arrived late enough in the evening that I didn’t see much on my way in, but inside the house on a side cabinet were a few of the largest heads of triticale I’d ever seen—bright, clean and perfectly heavy. But of course, I’ve known for years that Bill and Rhonda fall into that category of ‘lucky’ farmers with ‘lucky’ farms. I could see there was a story here, and I went to bed primed to get up early and find out what it was.

The next morning, barely after first light, Bill took me on a tour of paddocks. The first one we stopped and looked at, the heads were bent earthward, nodding as though soaked in a heavy sleep. We had seen neighbouring paddocks on the way in, but I hadn’t recalled any bending with so much weight, so I looked around, and sure enough, one right next door was standing erect, with only the slightest stoop to the heads. I rubbed up a couple heads of each, and sure enough, Bill’s triticale was fat as foundation seed, while there was little else but chaff next door.

“He’ll have to bale it. He won’t be able to harvest it.” Bill said. “We only got 8 inches of rain for the whole year last year, you know, and he’s chemical.

“Well, I guess. But it sure is a big difference. D’ya know why it’s sooo different?”

“Well, we put compost from our own operation [Bill and Rhonda’s humified compost operation is a model] on this one and we’re biological so we use inoculants, teas, a little kelp and things like that. I’m set up to liquid inject when I plant so I don’t use all that much stuff but it goes right on the seed and pretty much ensures a good strike and a bang of a start. It’s pretty near all organic stuff we use, and, of course we don’t treat our seed—we want micro-organisms to come running to the feast and interact with roots as soon as possible when they sprout.”

“Well, sure. Compost, organic ferts and beneficial microbes help. And there’s no question that organic matter—good old carbon—is the best attractor of hydrogen in the periodic table; whereas salt ferts are harsh and make plants thirsty as if they were drinking sea water—must drive crops nuts. But I was talking about a bigger difference even than that. You’ve undersown this with clover. What kind of clover is this?”

“It’s arrowleaf; good strike, eh? It really likes to grow in the winter here, especially under grain.”

“That’s what I mean. It’s beautiful, just about full closure. Let’s take a look at what’s happening underneath.” I knelt down and parted the vegetation, sorting through it with my fingers. There was hardly any bare soil and there were tiny white arthropods of some sort scurrying to and fro at a pace that would have shamed most ants. I don’t know the name of that species, though I know they are beneficial; and I didn’t try to count them though it looked like in 200 square centimetres there would have been sixty or eighty, maybe a hundred, maybe more since they probably weren’t all on the surface. There were other creatures too, some smaller, some larger. And there were holes, the surface doorways of larger more subterranean beasts, scattered here and there as well. “Man, this place is alive, Bill! What d’ya reckon they drink at night if it doesn’t rain—which it hasn’t done much of here in recent years?”

“Well, if I was them, I’d drink dew.”

“Me too, and there’s two dewfalls per night, too—one at sundown and one just before sun up. Don’t tell me you’ve only had 8 inches of rain the whole year—you’ve caught that much in dew, and a lot of it because you’ve got so much habitat and so many helpers, coming up at night for water and tucking into the soil and munching microbes and stuff like that while watering and feeding your grain. So much for the ‘competition for nutrients and moisture’ theory. Any damn fool could see you’re disproving it, though they’d have to look, of course.”

That morning before breaky Bill and I must have visited most of the paddocks he hadn’t harvested yet, and they were all pretty similar; some as good, some a bit weaker and patchier, all with a crop of grain in a region where both rain and grain were all too scarce. I gave him an earful about how the triticale gives off alkaline root exudates and hosts endophytic microbes (e.g. actinomycetes) that unlock silica—essential for cell walls and transport—from the clay (aluminium silicate) colloids; while the clover gives off strongly acidic root exudates and unlocks calcium which is the main feedstock for bacterial nitrogen fixation.

Later on I had a chance to check out the composting operation, where I was surprised by their scientific grasp of things, their professionality and the quality of the finished product. I had come down from Far North Queensland to see this, since I hadn’t been there in three years; and back then they were only in the bare beginnings of making compost—although that’s another story, perhaps for a later time.

The real surprise was the absolute beauty of Bill’s undersowing of arrowleaf clover in his triticale and the quality and quantity of his harvest. I asked him if he got much clover seed when he harvested his triticale.

“Hardly any.” Bill allowed in wistful disgust. “I might wish. I’d thought there’d be more, but no such luck. I’ve got seed cleaning equipment and it sure would be easy to separate—and a lot more valuable than triticale too.”