Production and evaluation of potassium fertilizers from silicate rock

Abstract

Rising price and limited geographical availability of traditional sources of potassium (K) fertilizers have stimulated a search for alternative K sources in different parts of the world. We evaluated mineral transformations and agronomic properties of an alternative source of K produced through thermal and chemical treatment of the verdete rock (VR). Chemical and mineralogical characteristics were evaluated before and after each treatment. Four K sources (verdete rock, KCl, acidified verdete, and calcinated verdete) were applied to a Typic Hapludox at different rates. Eucalyptus and sequentially cropped maize and grass were grown in the treated soils. Verdete rock, which contained glauconite and microcline as K crystalline minerals, had very low solubility in water and in citric acid. Thermal and chemical treatments increased the concentration of water soluble K and citric acid soluble K. These treatments also caused crystalline K minerals to collapse and form sylvite and arcanite. Untreated verdete rock was not suitable as a K source for maize (Zea mays L.) and eucalyptus (Eucaliptus urograndis I144). Thermal and chemical treatments increased agronomic performance of VR to be similar to KCl. When K was applied as K‐calcined verdete, 82% of the total K was recovered in maize and grass cultivations. Less K was recovered in plant following addition of K‐acidified verdete and KCl (72% and 77%, respectively). Potassium recoveries by eucalyptus were about 52, 53, and 60% of the amount applied of calcined verdete, acidified verdete, and KCl, respectively. Both calcination and thermal treatment increased the K uptake and dry matter production for all plant species tested to be similar to KCl suggesting that this silicate rock could be beneficiated to be an effective K fertilizer.

Nutrients release from powder phonolite mediated by bioweathering actions

“…However, by the increase observed at the treatment with only powder rock, even at the short period of evaluation, there is an expectation that in a medium-long term, better results could be observed. This hypothesis is supported by the data presented by Santos et al (2016), which had responses to the verdete rock application solely in a medium term.…”

Assessing the Availability of Terrestrial Biotic Materials in Product Systems (BIRD)

“…Only phosphorus and no other soil nutrients are considered, because phosphorus is a limited resource itself and thus can limit the production of agricultural products significantly. Other nutrients like potassium, calcium, sulfur, magnesium and nitrogen (which can be easily extracted from the air e.g., via Haber-Bosch process [81]) are not considered being scarce as they are available in great quantities within nature or can be easily recycled [82][83][84]. Thus, limitations to their availability are not expected in the near future and, therefore, not included within this approach.…”

Alternative sources of potassium for maize cultivation

“…There are challenges related to the use of rocks as fertilizers, such as providing nutrients in the correct amounts and at the right time for each crop (Harley;Gilkes, 2000). Studies showed that most Brazilian rocks, such as glauconite, present low capacity, or are even not able, to supply K to plants (Santos et al, 2016;Silva et al, 2012), especially in rocks with potential K sources, consisting of silicate minerals, potassium feldspars, micas, vermiculites and smectites (Curi;Kämpf;Marques, 2005).…”

“…The process of calcination (Martins et al, 20015) and acidification (Santos et al, 2016) of glauconite was efficient to increase K solubility when extracted in water and citric acid. The effect of these processes also enabled the increase of K availability for Mombasa grass and maize when compared with the use of fresh rock (Santos et al, 2016).…”

“…The process of calcination (Martins et al, 20015) and acidification (Santos et al, 2016) of glauconite was efficient to increase K solubility when extracted in water and citric acid. The effect of these processes also enabled the increase of K availability for Mombasa grass and maize when compared with the use of fresh rock (Santos et al, 2016). Moreover, the calcination process was also efficient to increase the release efficiency of K in glauconite in ornamental plants (Boldrin et al, 2019) and in millets (Duarte et al, 2015).…”