Soil Organic Phosphorus Cycling Around the Roots of a Native Grass in Two Contrasting Tropical Savannas

• Published in: Journal of soil science and plant nutrition 2022-09, Vol.22 (3), p.3479-3489
• Main Authors: López-Gutiérrez, Juan C., Toro, Marcia, López-Hernández, Danilo
• Format: Article
• Language: English
• Subjects: Acidic soils; Agriculture; Anthropogenic factors; Arbuscular mycorrhizas; Biological activity; Biomedical and Life Sciences; Colonization; Cycles; Ecology; Efficiency; Environment; Fertility; Fertilizers; Flowers & plants; Fractions; Grasses; Grasslands; Life Sciences; Microbial activity; Microorganisms; Mineralization; Nutrition; Organic phosphorus; Organic soils; Original Paper; Phosphorus; Plant Sciences; Potassium phosphate; Potassium phosphates; Rock phosphate; Roots; Savannahs; Seasons; Soil fertility; Soil Science & Conservation; Soils; Symbiosis
• ISSN: 0718-9508; 0718-9516
• DOI: 10.1007/s42729-022-00901-0

Savanna ecosystems in northern South America possess acid soils, low phosphorus (P) fertility, and low primary productivity. Dominant C 4 tussock grasses, such as Trachypogon plumosus , are the main contributor to total biomass production in neotropical savannas. Soil microbial activity, mineralization of organic P, and arbuscular mycorrhizal (AM) symbiosis are essential for understanding the adaptation of plants to the low P fertility. We selected a low P-sorbing Entisol and a high P-sorbing Vertisol, at Estación Experimental La Iguana located in the Orinoco Llanos in northeastern Venezuela, with T. plumosus as the dominant plant component. We monitored changes in organic P fractions, P transformation rates, dehydrogenase activity (DHA), acid phosphomonoesterase activity (APA), and AM status after P addition as a soluble phosphate salt, K 2 HPO 4 , or a slow release rock phosphate. Fertilizer addition resulted in a doubling of P-shoot content in plants growing in the Vertisol and no significant difference in the Entisol. Microbial activity, APA, and P transformation rates responded to P addition in the high P-sorbing Vertisol, but not in the low P-sorbing Entisol. Less available organic P fractions were affected by P addition from both sources. Although no differences in AM colonization were found, the high AM colonization demonstrates that T. plumosus functions as an obligate mycotroph. A deeper understanding of P cycling in the soil surrounding the roots of native savanna grasses will allow us to better respond to the anthropogenic pressures on these ecosystems.