Much has been written on what it takes to have a successful vegetable gardening experience, so it is difficult to know where to start without repeating what has already been published on this subject. Let’s begin by establishing some basic principles essential for a successful vegetable gardening experience that I have categorized into 9 subject matter topics: soil testing, liming, fertilizing (inorganic versus organic), organic matter supplementation, tillage, irrigation, crop rotation, cover crops and plant analysis/tissue testing.
Too many home vegetable gardeners fail to have their garden soil tested. Soil testing services and laboratories are readily available with the cost for the test more than offsets losses that can occur by not knowing the fertility status of the soil, and in turn, to learn what is needed to correct uncovered nutrient element insufficiencies. An imbalance among the essential plant elements is not an uncommon occurrence if the gardener is applying commonly advertised fertilizer materials without regard to the soil’s existing fertility status. The common essential element insufficiencies occurring in many vegetable garden soils is an excessive level of phosphorus (P), and the lack of balance among the major cation elements, potassium (K), calcium (Ca) and magnesium (Mg). An excessive level of soil P is almost impossible to correct, while the imbalance among the three major cation elements can be corrected with the proper use of fertilizer and liming materials. High P will interfere with the absorption and plant bio-chemical functions for several micronutrients, mainly copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn). As for an imbalance among the 3 cations, it can result in deficiencies of Ca, and particularly Mg, affecting fruit yield and quality for some fruiting vegetable species, such as tomato, pepper, cucumber and melons.
Failure to maintain the soil pH within the desired range is probably the most common deficiency when cultivating natively acid soils. In the arid regions of the country, soil alkalinity is the common soil condition that takes special treatment and cropping conditions to be successful. If soil acidity is the issue, a soil test result will give what is needed to bring an acid soil into the designed pH range. A liming recommendation will specify the quantity of lime needed as well as the form, recommending dolomitic limestone if magnesium (Mg) is needed. The liming material recommended should be applied in the fall and worked into the soil to the plow or spade depth. If the soil was found to be strongly acidic, a substantial quantity of a liming material may be recommended. When large quantities of lime are applied, there will be a period called “lime shock” that can adversely affect seed germination and early seedling growth; therefore the soil should be allowed to stand for several months before planting.
Fertilizer Selection and Use (inorganic and organic)
Accompanying a soil test result, and with the plant species to be grown given, a fertilizer recommendation is generated that corrects any soil nutrient insufficiencies as well as specifying those elements needed to satisfy the plant nutrient element requirement. There are 2 concepts associated with fertilizer use, applying that needed to establish and maintain a particular nutrient element sufficiency level, or applying just that amount of a nutrient element needed to satisfy the plant requirement. The former concept gives the best results. A common error is to over-fertilize, adding more than what is needed – too much being as detrimental as not adding enough. The only major element recommendation that is not based on a soil test result is nitrogen (N). Its determination is based on the requirement of the plant species. Insufficient N will result in poor plant growth, while over-fertilization can subject the plant to easy insect and disease invasion as well as reduce flowering as well as adversely affecting fruit yield and quality. For best results, a N fertilizer should be applied just at planting or transplanting. In some instances, a N recommendation is be split, applying half the requirement at planting and then side-dressing along the plant row or around the plant itself in the middle of the growing period.
Foliar application of a fertilizer material designed for such use will normally have little affect on the nutritional status of the plant. Element adsorption depends on many factors, such as the form of the element applied, the characteristics of the wetting agent, leaf structure, time of day and climatic conditions – therefore certainty of adsorption is not assured. In addition, even if an element is adsorbed, it may not move beyond the point of absorption. Since water and elemental movement in the plant is upward, the absorbed element will move in the direction in which water moves within the plant. In some instances, it is that which runs off the plant that determines any plant response to a foliar fertilizer application.
Substituting an organic source for an inorganic fertilizer can result in poor plant growth when there exists a high nutrient element requirement. Organic forms of fertilizer, such as manures and composts, can vary considerable in their elemental content and their biological stability can result in plant nutrient insufficiencies. Greater skill is needed by those who wish to garden “organically” in order to avoid nutrient element insufficiencies from occurring, particularly for those vegetable species that have high nutrient element requirements.
How the soil is prepared prior to seeding or transplanting can significantly affect the soil structure and the distribution pattern of applied amendments. The objective is to develop a deep consistent physical and chemical rooting profile, either by plowing or hand spading, turning the soil over as the means of uniform mixing. For soils high in clay and/or organic matter content, clods may form if the soil is tilled when wet, clods that can be difficult to break up and result in poor mixing. To keep such soils friable, they should be spaded or plowed only when slightly moist. Roto tilling a soil, although it does create a fine textured seed bed, can destroy the soil’s natural structure, and when the soil is wetted, it will puddle and a crust will form on the soil surface that will reduce water and air infiltration. A surface crust will easily form on silty-type soils following rain or irrigation, a crust that should be broken by periodic light tilling.
Organic Matter Supplementation
Adding manures and composts can contribute to the characteristics of the physio-chemical properties of some soils, particularly for natively sandy soils. However when applied indiscriminately, they can generate physical and chemical properties that will make for infertile soil conditions. With an increase in organic matter content, a soil will remain wet and cold longer in the early spring and will drain more slowly after a rainfall event or applied irrigation. High organic matter content soils tend to be sticky when wet, therefore more difficult to till when being prepared for seeding and/or transplanting. The elemental composition of the organic material applied should be known for the quantity of elements applied will contribute to the soil’s fertility status. How much and when an organic material should be applied to a soil is a difficult determination to make. The objective is to generate and maintain a soil that has a friable physical characteristic.
Moisture stress – normally observed as plant wilting – is not an uncommon occurrence when either rainfall or applied irrigation water is insufficient to meet the plant water requirement, particularly on high atmospheric demand days. Plants can also wilt after a daytime rainfall event if the rain water is cold (less than the ambient air temperature) and/or when the soil becomes temporarily saturated creating a short period of anaerobic soil conditions. During periods of insufficient rainfall, knowing when to irrigate and how much to apply is not an easily made determination since adding too little or too much water can adversely affect plant growth. Between intermittent rainfall events, the objective is to irrigate so as to maintain some consistency of soil moisture conditions within the rooting profile. For best plant water utilization, apply irrigation water in the early morning hours or after sunset.
Vegetable gardeners tend to plant the same plant species in the same location in the garden in order to make plant tending and harvesting easier. Continuous cropping with the same plant specie in the same place can eventually lead to root disease occurrence. Under a monoculture system, populations of a few soil organisms will increase in their numbers with less diversity of specie type. A high population of a single organism can then become pathogenic to the host plant. To break this cycle, plant species should be rotated within the garden plot. Some degree of biological soil organism control can also be gained by planting a cover crop, a cool season grass, such as rye or wheat, between seasons. However when preparing the soil for the summer crop, it will be necessary to completely overturn the soil so that the cover crop doesn’t become a weed problem.
Plant Analysis/Tissue Testing
When visual plant symptoms due to either a suspected nutrient element insufficiency or plant disease, proper identification is essential if the problem is to be corrected. Nutrient element insufficiencies can be verified by means of a plant analysis (sometimes referred to as a tissue test), a service that is provided by most soil testing laboratories. It is important that sampling and submission instructions be obtained from the laboratory prior to collecting and submitting a plant tissue sample. Besides the analytical results, a plant analysis report will include instructions on how to correct a nutrient element insufficiency if occurring.
An effective means of monitoring the nutrient element status of the soil/plant system is to routinely collect plant tissue samples for analysis. Plotting the results over time, the changing pattern of plant nutrient element status as well as soil test results can be combined as a means for determining future lime and fertilizer treatments. Such a monitoring and interpreting program requires professional assistance that some soil testing/plant analysis laboratories provide.
For those wanting maximum results from applied inputs, following these 9 steps will provide that needed for successful plant and fruit production.
J. Benton Jones, Jr. has a PhD in Agronomy and is the author of several books including Hydropopnics: A Practical Guide for the Soilless Grower and Tomato Plant Culture. Dr. Jones has written extensively on hydroponic growing and outdoor vegetable gardening.