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Saturday, May 23, 2009

solanaceous group of vegetables and their nutrient Requirements

The solanaceous group of vegetables (tomato, eggplant, chili and bell peppers) generally take up large amounts of nutrients.  specially when grown under "general hydroponics" .The amount of nutrients they take up depends on the quantity of fruit and dry matter they produce, which in turn is influenced by a number of genetic and environmental variables .

Fruit and fruiting parts in this group of vegetables contain 45 to 60% of total N, 50 to 60% of total P, and 55 to 70% of total K absorbed by the plants. The major proportion of the advance  nutrients in fruit are absorbed from the time of flowering. The proportion of nutrients found in fruit declines with an increase in nutrient applications. A small proportion of the N, and still smaller proportions of the P and K, found in fruit are translocated from the vegetative parts.

The period of greatest  hydroponics nutrient requirements for N, P and K is from about ten days after flowering to just before the fruit begins to ripens.These crops use only a small proportion of N from organic sources. Eggplant is very effective in making use of plant nutrients already available in the soil, whereas tomato, and chili and bell peppers, are not. All these crops prefer NO3-N as a source of N. High concentrations of NH4-N in the growing medium greatly reduces their growth and productivity, especially of tomato and pepper.

The quantity of nutrients to be applied depends on the yield potential of the cultivar, the level of available nutrients in the soil, and growing conditions. Because in these crops vegetative and reproductive stages overlap, and because the plants need nutrients even up to fruit ripening, application methods such as fertigation, split application of fertilizers, use of slow release N fertilizers, and integrated use of fertilizers and organic sources of nutrients have proved very effective in increasing nutrient use efficiency and crop productivity, and reducing nutrient losses.

There are three important solanaceous vegetable crops grown for their fruits viz., tomato, eggplant and pepper. The last crop includes two cultivated types- hot or chili pepper, which is consumed either fresh or dried, and bell pepper, which is eaten fresh. All crops in this group are grown as annuals, and have much in common with regard to nutrient requirements.
Tomato is a deep-rooted crop. Its roots grow to a depth of 120 - 150 cm or more, unless they are restricted by an impervious layer of hardpan, a rock layer or by a high water table. Eggplant and pepper are medium-rooted crops, with roots which extend to a depth of 120cm.
The amount of nutrients taken up by these crops depends on the number of fruit and the amount of dry matter produced.

Varieties which take a long time to mature require more nutrients than short-duration ones, mainly because of their higher production of dry matter and fruit.Eggplant is a long duration crop, with high yields which remove large quantities of plant nutrients. Pepper needs to absorb more nutrients than tomato or brinjal to produce a unit of dry matter or fruit yield.

In tomato, the period when plants have the greatest requirement for K, N, Ca and P is just before the fruit begin to ripen . In pepper, the greatest requirement for N, P and K is during the period from about 10 days after flowering to about 30 to 33 days from flowering .

Tomato requires a large quantity of available plant nutrients. It can utilize only a small percentage of the inorganic N available in the large volume of soil explored by the roots. In N-rich topsoil, there will be poor root development, which could explain the low fertilizer N use by tomato । Unlike tomato and pepper, eggplant is very efficient in making use of plant nutrients already available in the soil .

The quantity of nutrients which the farmer needs to apply depends on the yield potential of the cultivar, the level of available plant nutrients already in the soil, and growth conditions. Since vegetative and reproductive stages overlap in this group of crops, they need a continuous and steady supply of nutrients throughout their life span. It is necessary to adopt appropriate nutrient management practices which help to supply advance nutrients in quantities adequate to just meet crop demand and minimize losses, thereby increasing the nutrient use efficiency. Such practices will be environmentally friendly, and lead to sustainability in vegetable production.
Fertigation with acidifying N fertilizers such as urea may sometimes have an adverse effect on growth and productivity।

Slow-release fertilizers hold great promise for the production of solanaceous vegetables such as eggplant and tomato.

The basic concept underlying the principles of integrated nutrient management is the maintenance, and possible improvement, of soil fertility for sustaining crop productivity on a long-term basis। Sustained productivity may be achieved through the combined use of various sources of nutrients, and by managing these scientifically for optimum growth, yield and quality of different crops, in a way adapted to local agro-ecological conditions. In vegetable production , farmers have been using organic manures for centuries, together in recent decades with chemical fertilizers, to meet the nutrient demands of crops. Integrated nutrient use has assumed great significance in recent years in vegetable production, for two reasons. Firstly, the need for continued increases in per hectare yields of vegetables requires that applications of nutrients increase. Not enough chemical fertilizer is available in many developing countries , to meet crop nutrient requirements.

Secondly, the results of a large number of experiments on manures and fertilizers conducted in several countries reveal that neither chemical fertilizers alone, nor organic sources used exclusively, can sustain the productivity of soils under highly intensive cropping systems .The integrated use of urea and poultry manure also resulted in a higher nutrient uptake .

The combined use of rye straw and nitrogen resulted in higher yields of tomato, eggplant and pepper than either N fertilizer or FYM used alone. Higher yields of chili with integrated use of chemical and organic fertilizers than with the use of either of these separately were obtained.

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