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Mailing Address:
The Robert H. Smith Institute of
Plant Sciences and Genetics
in Agriculture
POB 12, Rehovot 76100, Israel

Administrator: Neomi Maimon 
Tel: 972-8-948-9251,
Fax: 972-8-948-9899,
E-mail: neomim@savion.huji.ac.il

Director: Prof. David Weiss
Tel: 972-8-948-9436
Fax: 972-8-948-9899
E-mail: david.weiss@mail.huji.ac.il

 

Topics in Fertilization and Plant Nutrition

SEVEN LECTURES ON IRRIGATION

Question:

What are the assumptions and the main explanations for the use of foliage nutrition for plants that are in difficulty?

Answer:

If the plant responds to spraying foliage with the nutrition elements - it means that it was in a situation of a lack of these nutritional elements. Fertilization through the roots cannot be substituted by foliage spraying, except to remedy a temporary lack through this. Urea penetrates the ??? of the leaves well and will be effective in situations of a lack of nitrogen. If it will also assist in the uptake of other materials - this is hard to give an assurance and requires testing. A lack of phos phorous is easily remedied by spraying, but when there is no lack - there is no response. The response to the spraying of nitrous potassium in many orchards arises from a lack of this element which is caused by insufficient fertilization, and probably res ults from a lack of potassium in the tree. Damage to the root area, its limited volume, attachment to the ground - all these will lead to a lack which foliage spraying can remedy.

Question:

Can the ripening of the fruit be directed with the assistance of nutrient sprays or with the assistance of fertilization (in a vineyard, for example)?

Answer:

When the plant is annual, finishes, obtains a great deal of phosphorous - the time for ripening seeds shortens and seniority is obtained. There is a great deal of authority for this. We did not deal much with vineyards. From the work of Ben Ami in ??? it is clear that the consumption of potassium by the ripening plant is substantial and vigorous, and dilutes the other plant organs. This reduces the activity of the leaves and limits the ability of the plant to fill the fruit with sugar. This happens with industrial tomatoes. At the time of ripening phosphoric fertilization should be reinforced and nitrogen fertilization curtailed so as to avoid encouraging excess growth of carbohydrates. Note: In Ramat Hagolan care is taken not to give a lot of potassium to the wine vineyard for fear of damaging the quality of the new wine.

Question:

Must the competition and antagonisms among the nutrient elements be taken into account and what type of care must be taken in this regard?

Answer:

Potassium does not compete with calcium. An excess of sodium can harm the uptake of calcium, but this is usually the result of an increase in the overall salination, and of specific competition between sodium and calcium for upta ke places of calcium in the root. Potassium and magnesium, in contrast, are antagonistic, as both of them form part of the overall soluble materials in the cell, and this can definitely harm the functioning of the magnesium in the cell by excess fertiliza tion with potassium.

Question:

Comparative tests of leaves from a damaged section to a normal section - should these be done or does the lack discovered in the leaves hide the real problem?

Answer:

A test of many factors can assist in diagnosis, although the test of a single factor is sometimes insufficient. In any event, the test of a "healthy" as opposed to a "damaged" plant assists in eliminating items that are suspected of causing the problem or locating them, and a combination of such factors assists in explaining the mechanism of the damage and its remedy.

Question: Acids ???? and ??? acid recently. What can be said about their us

efulness? At Hof Hacarmel it was found that ??? acids were very good for bananas.

Answer:

??? acid is an essence of organic material, whose composition is not defined or constant. The usefulness of ??? acids cannot be predicted, primarily in varying grounds. It may be that a particular improvement in construction wil l occur in loamy soils. The ??? acids have chelation in ability which can lead to benefit in flowing solutions and rock wool. It has been reported that ??? acids have led to a reduction in the nematode population of banana roots. Theoretically it may be possible to assume a mechanism in which the ??? acid materials have an influence in blocking identification sites on the root against an occurrence mechanism of the nematodes and in this the reduction of the infection, but a large quantity of material is required for this. (With regard to ??? acid I have no data and therefore I do not know). Question: In the Jordan Valley there are high concentrations of boron which damage the ground. How can boron be removed from the ground and what can be done to remedy boron damage in vineyards? Answer: In the Jordan Valley there is a problem as a result of the geology - certain levels contain a great deal of boron. Sensitive crops should be avoided on such ground. If there is a crop on these lands - it must be irrigated very superficially in order to prevent the plants absorbing the boron, which is usually found at deeper levels. The irrigation must be precise and carefully directed, to main tain the active roots 20cm above the boron-rich layer. It may be possible by Tufa canals to direct the root areas outside the area of the boron influence.

Question:

Magnesium is generally given in spraying. Is it effective to give it in the ground, or in irrigation water?

Answer:

The water in the Israeli water carrier includes about 2 meq/litre magnesium (about 24 MG/L). There is accordingly usually no lack of magnesium. In the Gaza Strip there are sources of water with little magnesium and there the lac k of this element in the plants is more frequent. The conclusion - adding mto the water - is effective, when there is no magnesium in the water naturally. Adding sea water to irrigation water increases the rate of magnesium relative to the calcium and potassium and remedies lacks. In saline solutions it is easy to see that while the salt water solution does not permit plant growth, sea water in the same concentration allows good growth, because the calcium potassium and manganese in it moderate the influence of the so dium on the roots.

Question:

Farmers who use drip irrigation and spread natural fertilizer near the sprinkler in orchards and vineyards believe that this is a good thing. Is this the case?

Answer:

If there are active roots in the fertilized area and it is wet, there could be a positive influence. It is reasonable that the benefit, if there is one, is from the improved nutrition of the plants. This can be calculated by estimating the quantity of fertilizer supplied in the natural fertilizer.

Question:

What is the best and quickest way to remedy a lack of the ??? elements - spraying or fertilizing through the water?

Answer:

If the lack is diagnosed optically, the surest and quickest remedy is by spraying. Regular nutrition through the ground can prevent a lack where it has been diagnosed in the past. The disadvantage of spray treatment is that the remedy is local and temporary, and repeated sprayings throughout the growth will be r equired. There are cases, such as the lack of zinc in the Huleh area in which the land ??? the zinc with such strength that only spraying of the leaves has any influence.

Question:

What is the importance of basic fertilization when it is possible to fertilize using drip irrigation systems?

Answer:

With regard to nitrogen it is surely necessary to rely at least on a large part of the fertilization in advance fertilization. With regard to phosphorous and potassium - the basic fertilization is important but the situation and the distribution of the roots must be taken into account. If the root volume is directed and limited with drip irrigation then there will be a "waste" of fertilizer in a sense from the basic fertilizer which is given outside of it and it is worthwhile directing the localised fertilization accordingly. For line crops - fertilization located in stripes will ensure improved fertilizer exploitation. If the next fertilized crop after that is a line or bed crop, the fertilizer can be located accordingly. Basic fertilization prevents a lack at the beginning of the growth, before irrigation, which sometimes cannot be fully remedied during the season.