By Philip A. Wheeler, Ph.D.
As a sustainable/organic agronomist, one of the most disheartening types of calls I receive on a regular basis are the ones that proceed as follows. “Hi, this farmer Joe Smith, I’m having problems with weeds/insects/low yield etc. on my soybeans. Of course I should expect lower yields, since I went organic a few years ago.” My first reaction is simply to ask, “Why would you knowingly make a transition to a new way of doing things (a change of paradigms) without preparing for that change in advance?” “Did you have soil tests done to see what minerals might be short?” “Were you aware that the mineral balances and amounts become very critical when nature has to operate on her own without large amounts of high energy inputs?” Besides, soybeans are considered nutrient scavengers. Why would anyone automatically think that organic soybeans should mean lower yield?
This problem arises when the assumption of organic is that you don’t do much of anything and just let nature take its course. There is also the philosophical approach that frowns on any “pushing” of the plant by outside fertilizer application or foliar feeding of organic nutrients. Not “pushing” may work in rich soils or when organic market prices are way above non-organic. Recently, commodity prices for organic crops like beans; corn and grain have dropped dramatically compared to the last 20-30 years. Yield or output has now become important. What many organic proponents also fail to realize is that the faster growing, higher yielding crops may actually be the most nutritious if grown with biological/sustainable or organic practices and materials.
Making the decision to go “organic” should be a series of known steps that take the major surprises out of the outcomes you can expect in each year of your transition. You can also evaluate your potential for success before you even start. Let’s consider some of the factors that you can evaluate.
Where is my farm located? This factor leads to discussions of soil types, rainfall, markets etc. If you are on deep Iowa top soil, organic corn is a good possibility, while southern blow sand doesn’t look good at all, even if you have water control. Supplying enough nitrogen in a low organic matter soil could be quite costly on a low value commodity. Location becomes less of a problem for graziers if rainfall is adequate or irrigation is available. The heat is a problem, but not an insurmountable one. The main problem is producing enough TDN (total digestible nutrients) or to state it another way, having a high RFV (relative feed value) to economically produce more meat for a lesser amount of grass consumed. Raising the RFV is mainly concerned with increasing the relative amounts of cellulose and hemi-cellulose in relation to lignin. The forage must also be able to transmit as much of the mineral requirement as possible from the soil to the animal. Mineral supplements out of a bag cost a lot more that minerals bought by the bulk ton as components of soil amendments such as: rock phosphates, humates, paramagnetic rock, kiln dust, green sand, nutrient clays, etc.
The above objectives can only be met by learning about and working with the soils you currently have. This article is the beginning of a series on soils, minerals, humus, energy use and manipulation, foliar or crown feeding and moisture retention. Let’s begin at the beginning.
In the beginning were minerals. These were formed under the scientific laws of nature under great pressure and heat in previous stars. They became incorporated in the earth at its creation and form what we call soil. Most of our soils come from volcanic ash or weathered rocks that contain the earth’s minerals. Minerals are the basis of all life on earth. Vitamins, enzymes, and hormones have no use or function in the absence of minerals. Only about 5 % of a good forage plant is actually made up of the minerals, (the rest is carbon, hydrogen and oxygen that come from air and water.) but that 5 % is very critical in its composition and relationships. Contrary to what is usually taught in standard agronomy, let’s assume there are six major minerals as we combine the usual N-P-K with the three secondary of Ca-Mg-S. Memorizing these six can be very beneficial to your forages/livestock/pocket-book because neglecting any of them will produce less than the quantity and quality your soil would like to be capable of producing.
The first mineral to consider is calcium (Ca). It is the prime mineral nutrient! It determines the total volume of your crop when adequate water, nitrogen and temperature are available. It is interesting to note the article in the Feb. 2000 issue of SGF on page 26. It reports on research that shows calcium is an important element in the tenderness of beef. It is also the most important element in a plant for energy production and transfer, communication, disease and insect detection and defense, nutrition, strength, etc. Of course it does the same things in your livestock and the humans that consume it. I’m sure you are aware of the osteoporosis (calcium deficiency) problem in the US. One might ask why we have that problem in a relatively well-fed nation.
The reasons are very complex, but an easy one to understand is the one concerning lime policies/teachings that have been predominate in agriculture since the early 50’s or the “dawn of the chemical age”. A conscious decision was made to make the addition of lime (the major and least expensive source of calcium) dependent on the concept of pH rather than on the actual amounts of calcium present. Since pH is affected by other elements/nutrients as well as bacterial systems, the chance for serious calcium shortages in soils developed. The problem was and is compounded by the fact that the usual chemical inputs affect the availability of calcium uptake, regardless of the physical amount present. Nature also allows for the masking of shortages by making visual calcium deficiencies hard to detect in a plant while wrecking internal havoc in terms of nutrition and disease immunity.
The solution to the problem is to apply calcium according to cation exchange tests (CEC) rather than pH. Almost all modern soil test labs report there findings in terms of CEC, so that just leave the task of interpretation to you or your advisor. Since many crop advisors in conventional agriculture are not sufficiently informed or trained concerning calcium, you are urged to become knowledgeable yourself. The two major sources of calcium are high calcium lime and gypsum. Hi calcium lime or CaCO3(defined as less that 10 % magnesium carbonate content) is the best source for pHs below 7. Gypsum or CaSO4 is the best source of calcium for those with pH’s seven or higher. Gypsum also provides highly available sulfate sulfur, which helps make better protein and thereby reduces insect attack.
The remaining five major minerals could be argued over as far as importance, but they are all interdependent. I will choose phosphorous (P) as the second most important because it helps to produce and transport energy (carbohydrates) in the plant. After all, the main reason we have plants is that they are factories for producing the food (energy) needed by animals and humans in nature’s scheme of things. Phosphorous is the catalyst that lets the plant combine water and carbon dioxide in the presence of sunlight into simple sugars. It is those simple sugars that go on to become/produce/provide energy for all the other parts of the plant. A grower can measure the productivity of his sugar factory right in the field with a simple inexpensive refractometer, but that is a story for another time.
Magnesium (Mg) is the center of each chlorophyll molecule (it is actually an antenna to capture sunlight and raise its energy for use by the plant) and therefore is an essential part of the sugar making process described above. However, magnesium is a two edged sword. Too much magnesium (as can be supplied by the use of ag lime, which is also called dolomite lime) can purge N from a system and/or harden up clay soils. If your soil gets sticky in the spring and hard like brick in the summer, you have excess magnesium.
Potassium (K) is the enabler in the system. It plays a regulatory roll in enzyme activity without a lot being incorporated into the plant. Potassium is the key element in determining the caliber or size around of your stalk or fruit. Small apples are a shortage of potassium. Potassium also has its downside. To much available potassium over phosphorous will increase broadleaf weed pressure. Also, the use of the standard source of K, potassium chloride or 0-0-60, almost 50 % of which is a chorine (bleach) causes serious problems with microorganisms. This precludes its use in any transition to organic agriculture, which is highly dependent on biological activity. Luckily, nature is forgiving and soils can be recovered from having been “bleached”.
Since we covered sulfur above, that leaves us with the non-mineral element nitrogen (N). Nitrogen is the electrolyte in the system. It acts like the battery acid in a battery to carry charged particles called ions such as Ca++, and SO4–. Not enough N and the system doesn’t flow; too much N and the soil’s natural process shut down so that we become dependent on the local supplier. Also, too much N draws insects and diseases as well as weakening stocks. Sustainable and organic growers try to get their N from legumes, manure and urine, compost, as well as fixation by azobacter from the air and soil humus.
From a scientific and business standpoint then, it looks like soil testing and mineral replacement, balancing or activation is the logical way to start a transition toward sustainable/biological/organic agriculture.