Boron, toxicity

Boron. The principal materials used are borax [1303-96-4] sodium pentaborate, sodium tetraborate, partially dehydrated borates, boric acid [10043-35-3] and boron frits. Soil appHcation rates of boron for vegetable crops and alfalfa are usually in the range of 0.5—3 kg/hm. Lower rates are used for more sensitive crops. Both soil and foHar appHcation are practiced but soil appHcations remain effective longer. Boron toxicity is not often observed in field appHcations (see Boron compounds). 

Cayton MTC. 1985. Boron toxicity in rice. IRRI Research Paper Series No. 113. Manila International Rice Research Institute. 

Table 29.4 Boron Toxicity to Some Terrestrial Plants...

Dani, H.M., H.S. Saini, l.S. AUag, B. Singh, and K. Sareen. 1971. Effect of boron toxicity on protein and nucleic acid contents of rat tissues. Res. Bull. (N.S.) Panjab Univ. 22 229-235. 

Gestring, W.D. and P.N. Soltanpour. 1987. Comparison of soil tests for assessing boron toxicity to alfalfa. Soil Sci. Soc. Amer. Jour. 51 1214-1219. 

Glaubig, B.A. and E.T. Bingham. 1985. Boron toxicity characteristics of four northern Cahfomia endemic tree species. Jour. Environ. Qual. 14 72-77. 

Gupta, U.C., YW. lame, C.A. Campbell, A.J. Leyshon, and W. Nicholaichuk. 1985. Boron toxicity and deficiency a review. Canad. Jour. Soil Sci. 65 381-409. 

Kluge, R. and W. Podlesak. 1985. Plant critical levels for the evaluation of boron toxicity in spring barley (Hordeum vulgare L.). Plant Soil 83 381-388. 

Maier, K.J. and A.W. Knight. 1991. The toxicity of waterborne boron to Daphnia magna and Chironomus decorus and the effects of water hardness and sulfate on boron toxicity. Arch. Environ. Contam. Toxicol. 20 282-287. 

Martinez, E, P. Matio, I. Bonilla, and E. Fernandez-Valiente. 1986a. Cellular changes due to boron toxicity in the blue-green Anacystis nidulans. Phyton 46 145-152. 

Riley, M.M. 1987. Boron toxicity in barley. Jour. Plant Nutr. 10 2109-2115. 

Sage, R.R, S.L. Ustin, and S.J. Manning. 1989. Boron toxicity in the rare serpentine plant, Streptanthus morrisonii. Environ. Pollut. 61 77-93. 

Finally, the most popular extractant for boron is boiling water (eg, McGeehan et al., 1989) and it is agreed in many countries that concentrations below 1 mg B kg-1 soil imply the likelihood of deficiencies in susceptible crops. In England and Wales, the National Agricultural Advisory Service classifies boron levels as follows 0-0.5 mg L 1 indicates severe deficiency, 0.6-1.0 mg L 1 implies a likelihood of deficiency and values >4.1 mgL 1 indicate the possibility of boron toxicity. 

The basic characteristics of B deficiency show that the youngest leaves are the first affected, steins are short, severely affected plants liable to have a shrunken appearance, growing points die, root growth is impaired, fruit formation is irregular and the fruits are deformed, and necrotic and watery patches develop in storage tissue. Although plants require B for normal development, additions must be small or boron toxicity will result. Plants greatly vary in their tolerance to boron. 

Finally, for a brine high in boron, toxicity levels can be determined by analyzing an extract of water from saturated soil. The critical threshold is around 2 mg L 1. Fortunately, boron leaches quite easily from a soil at circumneutral pH, and if a soil is reclaimed from sodium, the chances are good that the boron would also be leached and its concentration would be less than 2 mg L l. 

Boron is concentrated in the kidneys during excretion, making the kidneys a prime target organ for boron toxicity. 

In arid conditions a soil content of boron > 30 ppm leads to boron toxicity for plants and animals. We can consider this value as the maximum permissible concentration (standard). Physiological and morphological alterations of plant growth are typical forms of boron toxicity. The animal toxicity is related to the decrease... 

In addition to the general osmotic effects summarized in Table 11.2, many plants ate sensitive to specific ions in irrigation waters or soil solutions. Boron toxicity is probably the most common. Table 11.3 lists some plants according to their sensitivity to the B concentration of irrigation water. Boron is more difficult to control than is salinity in general because it leaches more slowly than more soluble salts. 

Nable RO, Banuelos GS and Paull JG (1997) Boron toxicity. Plant Soil 193 181-198. 

Boron Toxic to plants Photometry, plasma emission... 

The first observation of boron toxicity caused by irrigation water was made in 1925 by Kelley and Brown (37). They associated specific injury symptoms with abnormally high concentrations of boron in leaves of walnut and citrus orchards in southern California. They noted that orchards irrigated with water containing 1.0 /xgram of B/ml or more frequently exhibited injury symptoms. In 1931, Scofield and Wilcox (38) concluded from additional studies of water supplies in southern California that the critical (injurious) concentration of boron in irrigation waters... 

Since most of the particles in PFA are in the fine sand range (0.2-0.02 mm), the texture of this material precludes its conversion into anything resembling agricultural soil. In addition, boron toxicity can be a problem when crops are grown on this material, although this is less likely if the ash is first covered with some topsoil. 

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