ACTA AGRONOMICA TOMUS 23. (A MTA AGRÁRTUDOMÁNYI KÖZLEMÉNYEI, 1974)

1974 / 1-2. szám - VARIA - R. R. SINGH-M. S. GANGWAR: Critical boron concentration and calcium-boron balance as related to the boron need of sugarbeet

VARIA 109 boron nutrition of promising sugarbeet varieties should be precisely studied. Thus, the present investigation was carried out with the following objectives: 1. To study the effects of added boron to soil on the quality and quantity of beet. 2. To study the relative susceptibility of sugarbeet varieties. 3. To determine the critical concentration of boron in leaf blade and to work out the calcium : boron ratio, which is helpful for the diagnosis of the boron requirement of sugarbeet. Green house studies were conducted with seven promising sugarbeet varieties and four levels of boron (0, 0.5, 1.0 and 1.5 ppm) on the silty clay loam soil of Nainital Tarai (India). The characteristics of the different varieties of sugarbeet used in the experiment are as follows: L26700, KWS—E, Hh-Sokeri and L29619 diploid, open pollinated multigerm varieties, 1JSH—9 a diploid, hybrid monogerm variety. Marocpoly and Resistapoly are anisoploid, hybrid multigerm varieties. The pH of the soil used in the experiment was 6.8. Exchangeable calcium and hot water soluble boron in this soil were 11.3 me. per 100 g and 0.78 ppm respec­tively. The processed soil was potted inpolythene pots(24x25 cm), each containing 10 kg soil. A basal dose of 100 ppm nitrogen, 40 ppm phosphorus and 30 ppm potassium were given. Boron was supplied through reagent grade sodium borate. Three replications of each treatment were maintained. Six germinated seeds were planted in each pot. The seedling plants were thinned to two after three weeks of growth. At the end of 95 days, the plants were harvested, washed with tap water, 0.01 N HCl and then with distilled water. The fresh root weight was recorded and then the roots were analysed for sucrose content by the cold extraction procedure of BROWN—ZERBAN (1941). Dry ashing for leaf blade samples was done, then the ash was dissolved in 5 ml. of 1 N HCl and the volume was made up to 50 ml. with distilled water. These solutions were analysed for calcium by the volumetric method using E.D.T.A. (HEALD 1965) and boron by the curcumin method (JACKSON 1967), Fresh beet weight, sucrose content and gross sugar yield. There was a significant increase in the fresh weight of roots upto 0.5 ppm added boron with the five varieties, namely KWS—E, Hh-Sokeri, L29619, Marocpoly and Resistapoly. Among these five varieties the fresh weight of the first three continued to increase, though non-significantly, even up to 1.0 ppm boron level and then it decreased with an increase in added boron above 1.0 ppm. But the fresh weight of the root in the last two varieties (Marocpoly and Resistapoly) decreased when boron was applied at the rate of 1.0 ppm or more (Table 1). In the remaining two varieties L26700 and USH-9, there was no significant increase in fresh weight due to the 0.5 ppm boron level. At 1.0 ppm boron, the fresh weight in the variety L 26700 increased significantly and then decreased. Variety USH-9 showed a decrease in fresh beet weight at 1.0 and 1.5 ppm boron. The average fresh weight of all the varieties indicated that the increase in fresh root weight with 0.5 ppm was 22.3 per cent and with the 1.0 ppm boron level was 24.7 per cent over the control. Besides influencing the beet yield, boron application also increased the sucrose content in beet resulting in higher sugar production. The application of 0.5 ppm boron increased the sucrose per cent and the gross sugar yield in all varieties but there was a decline in gross sugar yield at 1.5 ppm boron in most of the varieties (Tables 1 and 2). This is ascribed to the decrease in fresh weight of the beet with 1.5 ppm boron. It was also observed that 1.5 ppm boron in­creased the sucrose per cent in some varieties which may be attributed to their genetic charac­teristics. The increase in sucrose percent due to boron application had also been recorded by HAMENCE—ORAM (1964). The effect of boron on the sugar content of the beet may be due to its possible role in sugar translocation (GAUCH—DUGGAR 1954). A relationship between the complexing property of borate and sugar translocation has been implicated. MCLLRATH—­POLSER (1956) have argued that boron prevents excessive polymerization of sugar at the site of sugar synthesis which leads to more sugar reserves in the beet. 8* Acta Agronomica Academiae Scientiarum Hungaricae 23, 1974

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