Potential of root acid phosphatase activity to reduce phosphorus fertilization in maize cultivated in Brazil

It is urgent to mitigate the environmental impacts resulting from agriculture, especially in highly biodiverse and threatened areas, as the Brazilian Cerrado. We aim to investigate whether root acid phosphatase activity is alternative plant strategies for nutrient acquisition in maize genotypes cultivated under fertilized and unfertilized conditions in Brazil, potentially contributing to reducing the use of phosphate fertilizers needed for production. Three experiments were performed: the first was conducted in a glasshouse, with 17 experimental maize inbred lines and two phosphorus (P) treatments; the second in the field, with three maize inbred lines and two treatments, one without fertilization and another with NPK fertilization; and the third was also carried out in the field, with 13 commercial hybrids, grown either under NK or under NPK treatment. Plant variables were measured and tested for the response to fertilization, differences amongst genotypes and response to root acid phosphatase activity. The activity of root acid phosphatase was modulated by the availability of P and nitrogen (N) in the soil and promoted grain filling of commercial hybrids in soils with low P availability. These results demonstrate that it is possible to select genotypes that are more adapted to low soil P availability aiming at organic production, or to use genotypes that have high phosphatase activity under P fertilization to reduce the amount of added P needed for maize production in Brazil.

Biomass residues improve soil chemical and biological properties reestablishing native species in an exposed subsoil in Brazilian Cerrado

Revegetation of exposed sub-soil, while a desirable strategy in the recovery processes, often fails due to extreme soil chemical properties, such as low organic matter and pH levels inhospitable to biological activities such as nutrients cycling and plant establishment. This is the case for approximately 800 ha of the Cerrado biome in Brazil, where erecting the embankment of a hydroelectric dam in the 1960’s stripped vegetation, soil, and subsoil layers thereby distorting the soil properties. This work evaluates the effectiveness of restoration management (RM) treatments, to restore the soil quality, including biological activity and chemical attributes. In a factorial scheme, RM treatments include the addition of organic residue from aquatic macrophytes (AM) at 3 rates (0, 16 and 32 t ha^-1), combined with ash from sugar cane bagasse of agroindustrial origin (BA) at 4 rates (0, 15, 30 and 45 t ha^-1). RM samples contrasted samples collected from undisturbed Cerrado (CER) as well as a degraded area without intervention (DAWI). The mechanized RM plots received amendments and reforestation of 10 Cerrado native tree species. After 5 years, vegetation covered up to 60% of the surface in RM treatments receiving AM32 + BA45. AM and BA residues promoted height increases in the introduced plants. All RM treatments promoted lower levels of Al³⁺ than DAWI and CER. The combination of AM32 over the rates of incorporated ash increased soil pH and K values similarly to CER. Microbial-related variables, such as microbial biomass-C was the largest in CER, followed by the RM treatments, and the lowest in DAWI. The microbial quotient was no different between CER and RM treatments. The addition of residues such as AM and BA increased the vegetation covered, improved chemical and microbiological indicators. Thus, the residues used aided the recovery process of intensely degraded soils in the Cerrado area.