Foliar Fertilisers

Absorption of H2O and CO2 takes place through the leaves of plants, but almost aU the absorption of the remaining nutrient elements (e.g. N, P, K) is via the root system. Foliar fertilisers are not considered worthwhile for supplying P but significant leaf absorption of N can however take place if it is applied in the form of urea. 

---

Many fertilisers for the treatment of deficiencies of trace elements are added to the leaves. In addition, uptake of trace elements from aerial sources through the leaves may have a significant impact on plant contamination, especially of elements such as Fe, Mn, Zn and Cu. Anthropogenic aerosols have been reported to bring about foliar deposition of Pb to a great extent (Streit and Stumm, 1993). Zieve and Peterson (1984) have reported the assimilation of diemethyl selenide through leaves of terrestrial plants. Roberts et al. (1975) found a significant absorption of foliar-applied Zn, Fe, Cd and Mg. 

Agricultural uses for ammonium thiosulfate take advantage of both the sulfur and ammonium content by blending with other nitrogen fertilisers such as urea (71). Some foliar-spray fertilisers contain ammonium thiosulfate together with other metal micronutrients (72,73). Ammonium thiosulfate or mixtures with ammonium nitrate can also be used as desiccants and defoliants in crop-bearing plants such as cotton (qv), soybean, alfalfa, rice, and peppers... 

---