The relationship of zinc (Zn) deficiency to phosphorus (P) toxicity was examined in ‘Emerald’ okra [Abelmoschus esculentus (L.) Moench] grown for 21 days (D21) in complete nutrient solution and then transferred to treatments with two levels of P (P1, P2 = 250, 2,000 µM P) and four levels of Zn (Zn1, Zn2, Zn3, Zn4 = 0, 0.25, 1, 2 µM added Zn).No symptoms of “little leaf” or “rosetting” developed in any plants. “Mottle leaf” symptoms developed as chlorotic and necrotic patches in the interveinal areas of the older leaves of Zn1 plants at P1 and in Zn1, Zn2, and Zn3 plants at P2. Thus, increasing the level of P induced symptoms which were eliminated by adding Zn.Treatments had little effect on dry matter at D45 and D63: at D111, low Zn depressed dry weight of P1 tops and even more markedly depressed dry weight of P2 tops, roots, and fruits.Increasing solution P increased the concentration and amount of P in all plant parts at all harvests. At D45 it also depressed Zn concentrations in all parts of Zn1 plants but in no other Zn treatment and in no treatment at later harvests.At Zn1, leaves had relatively low concentrations of Zn and high concentrations of P. Increasing levels of Zn enhanced their Zn concentrations and depressed their P concentrations; at D45 and D63 they also depressed the concentrations and total amounts of P in tops and whole plants but increased them in roots. Thus Zn deficiency markedly enhanced P absorption by roots, transport to tops, and accumulation in leaves.Concentrations of magnesium in plant organs responded to treatments in the same way as did P but to a smaller degree, particularly in the leaves. No other element measured (Ca, K, Na, Fe, Cu, Mn) responded in the same way.The development and intensity of symptoms in old leaves correlated closely with P concentrations. Leaves with faint symptoms had 0.8% P; those with marked symptoms had > 1.5% P; and dead leaves had nearly 5% P. The intensification of symptoms is attributed to accumulation of P to toxic levels in leaves.It is suggested that Zn deficiency interferes with P metabolism enhancing the amounts of P absorbed by roots and transported to tops: under conditions of high P supply, P accumulates to toxic levels in leaves inducing or accentuating symptoms resembling Zn deficiency. This effect of Zn on P metabolism in roots seems to explain previously puzzling observations in which P treatments enhanced symptoms of Zn deficiency without any reduction in Zn contents of plant tops: there is no need to invoke any effect of P in inactivating Zn in leaves.

A map showing the regional distribution of Se concentrations in crops in the U. S. has been prepared, utilizing previously available and newly acquired plant analyses. The boundaries of areas on the map were based primarily on soil and geological information. In the Pacific Northwest, Northeastern United States, and the Southeastern Seaboard States, there are extensive areas where crops are generally low in Se.

Highlight: Soil ingestion was determined for cattle grazing a Bromus tectorum range in southern Idaho by measuring titanium concentrations in animal feces collected at 2-week intervals during the droughty 1973 grazing season. The experiment was based on the premise that titanium, which is abundant in soils, is contained only in small quantities (less than 1 ppm) in plants not contaminated with soil. Fecal-soil values averaged 14%, with values ranging from 3 to 30% of fecal dry matter, increasing as forage availability decreased. Soil ingestion levels were estimated to range from 0.1 to 1.5 kg with a median of 0.5 kgsoillanimal-day. This soil was ingested primarily with the roots of Bromus tectorum, which were often pulled up and consumed with the aboveground plant parts. Dust on leaves and stems accounted for only a small portion of the ingested soil. Measurements of acid-insoluble residue concentration in feces overestimated soil ingestion because of the probable presence of SiOZ of plant origin. Large changes in forage SiOZ concentrations of the diet reduce the effectiveness of this method compared to the Ti method. Ingested soil may be a possible source of trace minerals, pesticides, heavy metals, and radionucleides that may be sorbed to surface soil particles.

The relationship of soil factors associated with reported areas of Mo toxicity in cattle in seven agriculturally important valleys in Nevada was investigated. The level of Mo in the plant was selected as a measure of the soil factors, but Cu, Co, S and P were also determined in a large number of the forage samples.The Mo content varied both with plant species and soils.

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