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With three organic research plots in different areas of the state, at least one should have soil conditions similar to what you would have at your own farm.

Organic plots at E.V. Smith

E.V. Smith has a sandy loam soil, common in the coastal plain region of the state.  This type of soil is very well drained, acidic, and low in organic matter and cation exchange capacity (CEC), which is the capacity to hold and store essential plant nutrients such as phosphate and potash.  The CEC at E.V. Smith ranges from 3.5 to 5.  The pH is also low, from 5.5 – 5.8, which means that even fewer nutrients will be available to plants. To raise the pH we will be spreading lime on the plots this spring. 

The tissue analysis that we had done on our tomatoes and peppers last summer showed them to be deficient in potassium and calcium.  We did have some problems with blossom end rot, which is a sign of calcium deficiency.  Our plan is to use an OMRI approved 8-5-5 fertilizer this summer.  The product should supply sufficient potassium, phosphorus, and nitrogen.  To supply organic matter, we are also planning to add some sul-po-mag for potassium, and some zinc sulfate.  Zinc sulfate is restricted in organic crop production.  It only takes a small amount to meet the needs of crops.  Care must be taken not to put so much that it contaminates the soil or adjacent bodies of water. 

The soil at E.V. Smith needs organic matter, which will help store nutrients and water.  We are now growing winter cover crops, which we will mow and leave as crop residue on the soil surface where it will decompose slower than with tillage.  Finally, we will add compost to the planting rows. 

North Alabama Horticulture Research Center at Cullman

The plots at Cullman Research Station have been in cultivation in the past with sufficient fertilizer applied to address any deficiencies.  The soil is a clay loam, a soil type commonly found in the northern areas of the state.  The soil at Cullman has a higher CEC (ranging from 7 to 20) than at E.V. Smith and the pH is almost neutral at 6.7-7.2.  Thus, the soil is able to store more nutrients, and the plants are able to utilize the nutrients more efficiently.

The soil tests showed high or excessive amounts of phosphorous and potassium. However, the soil tissue analyses still showed that the tomatoes and peppers were deficient in potash and that the peppers were also deficient in phosphate.  Like most organic farming systems, our plots still need nitrogen and organic matter.  We plan to use the same 8-5-5 fertilizer at Cullman that we will be using at E.V. Smith.   We will not apply any additional potash or phosphate because the soil tests indicated that soil levels were already high.  We will keep an eye on the plants for possible symptoms of deficiency. 

Winifred Thomas Research Station

Winifred Thomas Research Station near Huntsville (Alabama A&M University), has clay soil that is acidic and low in plant nutrients.  The area had not been farmed for a long time prior to when we started our organic research in 2005.  Indeed, at the beginning of the project the research plots were a grassy lawn .  The soil needed lime, phosphorous, potassium, and organic matter. Last spring we added 2 tons of lime/acre, steamed bone meal (faster acting than phosphate rock), and composted, pelletized chicken litter (4-2-3) to supply needed plant nutrients.  Winter soil analyses showed the plots to be too acidic (pH = 5-6), and many of the plots were still deficient in P and K.  The CEC ranges from 8.3 – 20, with most of the plots being 8 or 9.  The tissue analyses showed the tomatoes to be deficient in P, K, and Ca, and the peppers to be deficient in P, K, Ca, and Mg.  This year we plan to add more lime, 8-5-5 fertilizer, soft phosphate rock, and sul-po-mag.

Conclusions

The soil deficiency problems encountered at our test sites are often common on farms transitioning to organic production.  It takes time to build up soil organic matter and a soil biological community that can process the organic matter and release and recycle the nutrients to the plants.  The best soil-building practices include cover crops, minimum tillage, addition of organic matter in the form of organic mulches and compost, and the addition of any needed rock minerals, which will release slowly through the action of soil microorganisms to yield a steady supply of nutrients.