Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

___________________________________________________________________________________Major Agronomic PracticesSecondary nutrients (calcium, sulfur, and magnesium) and micronutrients (boron, copper, iron,manganese, molybdenum and zinc and chlorine) are essential for growth, but required in smallerquantities than N, P, and K. Usually, secondary and micronutrients are lumped together undermicronutrients, also called trace elements. Addition of micronutrients should be made only when a cleardeficiency is indicated, preferably by a soil test analysis.Some of the micronutrients are found in the mineral particles of the soil but most come from thebreakdown of organic matter. The micronutrients exist in very complex forms and have to be brokendown into simpler forms which the plant roots can absorb. This process is comparable with thebreakdown of leaves in the soil: slowly they will become soft, fall apart into very small pieces andeventually disappear. This breakdown process is done by micro-organisms, mainly bacteria that live inthe soil. That is why it is important to stimulate the biological activity in the soil: it results in better soilfertility! To function effectively, the micro-organisms need air, water, neutral soil (pH 6 to 7.5) and lots oforganic material.Organic material usually contains both the macronutrients N, P and K and a mixture of micronutrients.3.8.2 Soil testingWhether or not chemical fertilizers need to be added depends on the amount of nutrients alreadyavailable in the soil. A soil-testing service can be a good way to find out if nutrients need to be added,and how much. In some countries, the Department of Agriculture provides a soil-testing service. Thereare also portable test kits that can examine the main nutrients of the soil. Results and reliability of theseportable kits however vary. The test kits are useful to find deficiencies of N, P and K butrecommendations for the amount of fertilizer to be added vary, according to local soil conditions.Soil testing usually does not provide information about soil structure, or biological activity, although someestimate of soil organic matter can be included.Past field history should be considered when interpreting soil test results. This is particularly importantwhen past fertilization has been in the form of organic materials which release nutrients slowly. In thatcase, soil tests may under-predict the amount of soil nutrients actually available to plants over the courseof the entire season (Peet, www1).Additional information on possible soil imbalances may be gained by looking not only at the leaves andtop growth of the plant, but by carefully digging up a plant, shaking off the soil, and examining the rootsfor vigor and signs of disease or pest damage. In general, roots growing in a fertile soil are morebranched than in a poor soil, and they have a profusion of root hairs. However, the plants must be dugup very carefully to avoid losing the root hairs. If the roots are growing laterally and are long and stringythey are searching for nutrients. If they are long and vertical, they probably need water. If they aregrowing only near the surface, the soil is too wet. If they are thick and short they may be suffering from atoxic element.healthy root system3.8.3 Role of organic matter and micro-organismsIn general, organic matter additions to a soil will increase its ability to hold nutrients in an available state.Organic matter additions will also increase soil biological activity. This, in turn, will affect the availability ofnutrients in the soil. Soil which has received organic matter has increased microbial populations andmore varied fungal species than soils receiving chemical fertilizer applications. The long-term objective of21Eggplant Ecological Guide