Rain Is Always A Good Thing For Crops Right?

I am often asked this question by non farm people, especially meteorologists.  You often hear the saying from traders, "Rain Makes Grain."  However, this isn't exactly true. . .  

It is true that crops need water to survive and produce grain, but depending on when, how, or how much it rains we can damage crops.  Early season moisture like we have had this year will and did drown out crops, prevented us from planting, and led to increase disease pressure in our fields.  The fact that it continued to rain during the early parts of the season also led to a phenomenon I call "lazy roots."  As young plants grow, if there is plenty of nutrients and water in the top parts of the soil they will not put roots deep as they typically would.  This in turn leads to problems when we get dry in that top few inches of soil.  Plants need water to uptake nutrients, so when the soil moisture content falls the plants cannot take in nutrients and then they will become nutrient deficient also increasing the drought effect. 

Phosphorus and Sulfur Deficiency from wet soil

A wet spring can also hurt us by moving our negatively charged nutrients like phosphate, nitrate, and sulfate through the negatively charged soil making it more difficult to keep them in the top 2' of soil where plants can use them.  We do use products that help keep nitrogen in the more stabil form ammonium which can bind to the negatively charged soil, but you have to put them on before you know how wet the spring will be. 

Potassium Deficiency from shallow roots

 In legume plants like alfalfa and soybeans that make their own nitrogen, wet weather can hamper their growth imensly.  For these plants to get nitrogen they have to form a symbiotic relationship with a bacteria we call rhizobia.  This bacteria takes the nitrogen that makes up nearly 80% of our air and breaks it down into a form that the plant can use.  If soil conditions are too wet there is no air getting to the bacteria to make nitrogen thus making these plants show nitrogen deficiency.

Nodules on alfalfa plants that house rhizobia bacteria

Ok, so if we have a dry spring that's even worse right?  Not really, in 2012 we had the driest start to a spring in 30 years and still ended up with near normal yields in most of my territory.  Part of this is due to a crop saving rain in the end of July, but the main reason we were saved was the water holding properties of our heavy clay soils.  We can handle dry spells early in the season, but at tassel in corn or podfill in soybeans if we don't get rain it can be a very bad thing.

Don't get me wrong, more often than not rain is a good thing.  It's funny how quickly though we can go from not wanting anymore to needing more, this year it took 3 weeks.  So the next time you are complaining about the weather, just imagine if your livelihood relied on it. . .

 Luke Bryan - Rain is a Good Thing