אסיף מאגר המחקר החקלאי

Nitrogen-potassium relationships in cotton growing II. A nitrogen-potassium fertilizer experiment with the Acala 1517 C variety

Year:

1970

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Volume :

19

Co-Authors:

Halevy, J., Div. of Soil Chemistry and Fertilization, Volcani Institute of Agricultural Research, Rehovot, Israel
Klater, E., Extension Service, Hadera District, Israel

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Abstract:

In this experiment the cotton variety Acala 1517 C responded markedly to nitrogen applications, as evidenced by increased lint yield and boll weight. There was almost no response to potassium except at the highest level of nitrogen (N120). When nitrogen was not applied, the addition of potassium depressed the yield. It may be concluded that as higher amounts of nitrogen are given to the plants, more potassium should be added, and vice versa. The response to nitrogen fertilization may be explained by the lack of available nitrogen in the soil. The amounts of nitrates in the upper layer and in the soil profile were not sufficient to ensure a good yield. When the amounts of nitrates in the soil profile are high, as a result of previous fertilizer applications and from mineralization of organic nitrogen, no response to nitrogen would be obtained. In the present experiment, even in the unfertilized plots, the amount of N-NO3 supplied by the soil profile down to 1.50 m was quite high (over 50 kg N/ha). At ΔF=-3750 cal/mole, potassium should be applied for Acala 1517 C variety. Feigenbaum and Golub (2) found that in most of the plots affected by leaf browning, ΔF values were lower than -3500 cal/mole. The potassium content of the leaves was less than 1% only in the N120K0 treatment. Such values are usually found at the end of a season in which potassium deficiency is serious (2, 5). The results of this experiment show that both ΔF values and potassium content of the leaves may be used as indices for potassium fertilization. Soil nitrate in the soil profile likewise seems to be good for assessment of the nitrogen needs of cotton. © 1970 Dr. W. Junk N. V. - Publishers.

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