Improving Soil Quality Naturally

Producing quality products while improving soil quality is a hard balancing act when growing horticultural crops. To compound the difficulty, we practice this on our farm without synthetic fertilizers and herbicides. In a perfect world we would grow all crops in a no-till situation, as can easily be done with large-seeded agronomic crops. With horticultural crops we are dealing with either very small seeds, and/or very high-density plantings of species that are not  adapted to this climate in the first place. This is to say that in a high-residue situation they do not compete well.  One dreams of the ease of growing no-till corn and getting the high returns of horticultural crops!
    
For more than ten years, we have been developing a system which maintains or improves soil organic matter content, by the conscientious use of summer and winter cover crops along with as little tillage as will get the job done. We use several tools and concepts to make this happen, as well as to monitor our progress.
    
First we soil test each rotational unit every late summer/early fall. We use the results to monitor the mineral fertility components of the soil (P, K, and pH). This gives us timely information on if and how much of these amendments we need to add in the fall, prior to seeding winter cover crops. We also are able to monitor soil organic matter content by watching how our CEC numbers are changing.
    
Because cation exchange capacity is made up of the exchange sites on both the clay particles and the stable organic matter, we can tell if we are adding or losing organic matter, because we certainly aren’t adding any clay to our soils! We have raised our CEC’s by 1-2 points in our sandy loam soils over the past 8-10 years. We’ve seen dramatic improvements in our clay soils; due to their less aerated nature and by the use of single applications of compost, we’ve witnessed increases of 7-8 points or even more.
    
Second, we have decided to add organic matter to our soils by growing it in place rather than hauling it in the form of manure, compost or other organic materials. This has required us to design our rotation to accommodate both summer and winter cover crops, sometimes by forgoing a cash crop with the knowledge that the benefits of growing a cover crop instead will provide a greater payoff in the long run.
    
With the goal of both maximum biomass production and nitrogen fixation, we always combine a grass with a legume. Depending on which crop is to follow, we match it with cover crops that will give the highest possible growth prior to incorporation or kill date. Oats/crimson clover planted prior to the late winter/early spring-planted cash crops, and rye/hairy vetch prior to the late spring/summer planted crops are two examples..  Similarly we use millet/soybeans prior to fall-planted cash crops, or for maximum biomass production, we plant sudex/cowpeas or soybeans prior to another winter cover.
    
In conjunction with the sudex covers we mow it several times during its 8-10 week growing period, partly for later ease of incorporation, but also to force it to send roots even deeper as recent research has shown.
    
Third, we have designed our rotation (10 years in length) both for maximum diversity for disease and insect management and, as much as practical, to alternate heavy feeders with light feeders, deep-rooted crops with shallow-rooted ones, and cool-season with warm-season crops.  This allows us not only to place cover crops into the rotational scheme at their optimum points, but also spreads out the “use” of the organic matter they provide in a balanced way. This also places heavy tillage, as often as possible, at times of the year when the conditions are less optimal for maximum soil biological activity, contributing to slower oxidation of organic matter.
    
We know that the optimum conditions for biological activity in the soil require four conditions: warmth, aeration, moisture and pH around 6.0.  By using this information we try to time our aeration (tillage) activities to times of the year when the soil is cooler and drier so that we burn less organic matter due to that aeration.  This means that we now do all of our deep or heavy tillage operations in the fall as we are preparing land for the next season and the winter cover crops.  This also coincides when we spread any mineral amendments for use by later crops.  All other tillage is as shallow as possible, just deep enough to incorporate the cover crop four weeks ahead of the cash crop planting date, to prepare the final seed bed, or a single cultivation for weed control.  This is part of the conundrum of trying to build and maintain organic matter while at the same time allowing for the mineralization of nutrients in that organic matter for use by the cash crops being grown.
    
For the past eight years we have been experimenting, implementing and increasing the use of an annual no-till system for those crops that we feel are most adapted to the conditions created by such a system. This is the system for vegetables developed at the University of Maryland and Virginia Tech, among other places. The benefits of no-till are well known both in terms of soil organic matter and biological life. The difficulties are mostly in the practical physical aspects of implementing it. These include establishment of a good stand that will leave enough residue for weed suppression; timing of and effective means to lay down and kill a huge cover crop without the use of herbicides; seeding rates that give the proper ratio of grass species (with high C:N ratio for season long residue) and legumes so that the nutrient release is timely for the cash crops use; planting both transplants and seeds into a high residue situation; and cooler soils associated with a heavy residue. Many of these are equipment-related issues, which on a small acreage are harder to achieve due to cost, availability or spacing constraints.
    
We have had success with and continue to grow sweet peppers, late-season tomatoes and squash and pumpkins in this annual no-till system.  We see the improvements to soil quality after one season of no-till and continue to find other crops that can be practically grown this way.
    
After over 20 years of farming, 15 years of using cover crops and 10 years of intensive development of the system we have seen a marked improvement of our soils. Indicators of this are higher CEC’s, more organic residues, more soil biological life, easier to prepare and
plant-to-seed beds, fewer disease and insect problems, healthier crops and higher yields. Our purchased inputs to the system are stable or reduced and our net returns are higher. Management inputs are higher but the returns to the manager are also higher. We know that there are still improvements to be made and new discoveries in soil biology to be made that will lead to those improvements. The highest possible soil quality is always the goal but all of the factors that contribute to improved quality, both theoretical and practical have to be considered.