Why too much precipitation is bad

This post from late last summer got lost in my queue and was never finished.  A moderate dry spell through April and May of 2011 has gone back to sogginess lately, so the contents of this post are still relevant and present good general knowledge about farming conditions regardless of what the rest of the year brings. And it helps explain why 2010 was so bad for so many people, after building on the wetness of 2008 and 2009. I’ve tried to update all the grammar to past-tense to account for this, but apologize if a few oddities sneak through.

(originally written late summer 2010)
I was chatting with someone a week or so ago, when they remarked that “boy, all this rain must be great for you farmers!” I paused, then treated the poor, well-meaning fellow to a thorough lecture on why too much rain is very much NOT great for most farmers.

Too much rain during spring and summer means crops can’t easily be planted, because equipment can’t get into the fields through the mud. Used on wet ground, machinery compresses the soil, leaves ruts, and otherwise does damage to the soil health. Even on a low-equipment farm like ours, where this isn’t a big issue, there’s still a limit to how well you can work soil when it’s completely saturated and thus there are problems getting things planted or transplanted in the first place. I talked to many growers at market in 2010 who  had to retill and replant things over and over, just trying to get them to germinate and grow properly.

The 2010-2011 winter of regular snow and rain has kept the ground at near saturation, meaning we couldn’t do any real work in the spring without damaging the long-term health of our soil. Even when we go a week or more without precip, it takes so long for soil moisture to leave Boone County’s high-clay soils that what feels dry to a town-person isn’t dry from a farm perspective. The few times the weather was dry in 2010, it lasted just long enough to start recovering from the last system before a new one set us back to square one. This is especially bad with snow, which takes much longer to go away than rain.

Heavy or constant rains create a lot of issues for growing plants. Young seedlings or transplants may be drowned in puddles, or have difficulty germinating. Constant moisture creates an ideal environment for many diseases, which can stunt the plants early or affect their later growth & yields. This is especially true for things like beans, tomatoes, peppers, squash, and other crops which rely on a single plant for large yields of fruit.


Saturated soils also cause many problems. Root crops like potatoes rot more easily; we lost most of our potatoes in 2010 and so did many other folks I talked to at market. The soil just stayed near saturation for weeks to months, and whatever potatoes did form rotted before we could harvest them (which is harder to do in mud than drier ground), even those at the top of raised beds. Also, most plants’ roots need some air in the soil to function properly. Plants growing in perpetually saturated soil end up effectively choking; they can’t function properly and so end up stunted or deformed.

The photos below (from 2010) show two ends of a single, equally planted row of pole beans. The first one is the south end, on marginally drier ground. The second one is the north end, in an extra-wet part of the field. Look how spindly and pathetic the bean plants are in the second one, despite being the same variety planted at the same time in the same soil of the same row (also note the weed-load, addressed below). This certainly cut into our yields for market and restaurants in 2010.

Too much rain also encourages weeds to go crazy. The soil always contains a seedbank of potential weeds; under excessive moisture these just keep germinating and quickly grow out of control. Hoeing is one of our most effective weed-control techniques, but it requires somewhat dry conditions (so the soil doesn’t just stick to the hoe) and it works best if (1) the weeds are small and (2) a bit of dry weather follows the hoeing so the weeds will dessicate & die rather than re-root after hoeing. If weeds get too big to easily hoe–which tends to happen more when it is wet, then the weed problem becomes a hand-weeding issue, and that’s much more time consuming than hoeing.

We spent a terrible amount of time in 2010 just trying to keep up with weeds, preventing us from doing other work. This is not just an organic/no-till problem, either. Growers of all kinds have to deal with weeds in their own way, and excessive pressure hurts everyone. On any drive through farm country north and east of here, we could see many conventional corn & soy fields with abundant weeds sticking up, even when those varieties are GMOs bred to resist herbicides (the rise of herbicide-resistant weeds is another factor). Everyone I talked to in 2010 bemoaned the labor/cost spent in dealing with excessive weeds.

For example, the photo below shows a portion of several potato rows. I dug the one on the left just before the photo was taken. There are two more beds in the center and right that I dug around a week beforehand, which looked like the left-hand one, and now look like an overgrown lawn. That’s how much weed pressure is put on every growing area with this much rain to keep new seeds germinating constantly, and new weeds growing quickly.

Even if a plant makes it to maturity and starts setting fruit (beans, tomatoes, cucumbers, etc.) too much rain encourages damage and disease. Our bush beans were terrible in 2010, partly because strong storms repeatedly flattened the plants and forced the developing beans down into the mud. They were so wet that the plants became diseased and most of the beans were deformed and damaged, and thus unsellable. What customers don’t see at market is all the product we don’t bring because it doesn’t meet our standards. Cucumbers and peppers also suffered from moisture-related damage and disease.

Also, too much rain can affect the taste and quality of fruit, particularly tomatoes. Many of these have had no flavor in the last few years, because too much moisture being taken up by the plants during ripening dilutes the flavor in the fruit; tomatoes taste best when harvested under near-drought conditions. A temporary dry spell at the end of summer 2010 finally produced some halfway-decent tomatoes for the first time in years.

I can’t entirely prove this connection, but 2010 was the worst pest year we’ve seen, causing lots of damage and helping spread disease among plants. In any case, many of these factors work together; plants already weakened or diseased from direct moisture effects are going to be more susceptible to pest pressure or damage. Organic management in particular relies on keeping plants healthy in the first place, the better to resist pests and disease, the same way that a fit, healthy adult can generally handle an illness better than a frailer person. So when we get really nasty weather conditions that weaken all the plants in the first place, it becomes a cascading effect of increased pest pressure, damage, and problems in the crops.

Wet soil doesn’t support roots very well, as anyone who’s lost a whole tree to a storm knows very well. The combination in 2010 of always-soggy soil with a series of strong, windy storms caused significant problems for crops which need to stand up, such as tomatoes, corn, beans, and peppers. As noted above, most of our bush bean plants were flattened by storms as the roots just couldn’t hold up, and much of our corn was blown down at one point or another. The tomatoes, even trellised, in many places collapsed into each other, forcing us to pick through a tangled jungle of foliage & stalks. Increased contact between leaves and ground leads to higher rates of disease and fruit problems, and the plants are more likely to break later on.

If you’ve gotten this far, you’ve concluded that we’d be better off farming in a desert. Well, there’s a reason why most of the US’s industrial agriculture is centered in places like southern California and Arizona, where weather is mostly not a problem. Of course, it takes massive Federal irrigation subsidies and severe environmental degredation to keep that industry competitive, but that’s another story. Most years in Missouri aren’t this wet, at least statistically. Since 1890, central Missouri has recorded only ten years in which annual precipitation went over 50″. Three of those were 2008, 2009, and 2010. We got off to the same start in 2011, before moderating somewhat in April and May. And many parts of Missouri have been wetter than we have on this farm.

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