Gina Garland

Organic phosphorus in the terrestrial environment: a perspective on the state of the art and future priorities

BackgroundThe dynamics of phosphorus (P) in the environment is important for regulating nutrient cycles in natural and managed ecosystems and an integral part in assessing biological resilience against environmental change. Organic P (Po) compounds play key roles in biological and ecosystems function in the terrestrial environment being critical to cell function, growth and reproduction.ScopeWe asked a group of experts to consider the global issues associated with Po in the terrestrial environment, methodological strengths and weaknesses, benefits to be gained from understanding the Po cycle, and to set priorities for Po research.ConclusionsWe identified seven key opportunities for Po research including: the need for integrated, quality controlled and functionally based methodologies; assessment of stoichiometry with other elements in organic matter; understanding the dynamics of Po in natural and managed systems; the role of microorganisms in controlling Po cycles; the implications of nanoparticles in the environment and the need for better modelling and communication of the research. Each priority is discussed and a statement of intent for the Po research community is made that highlights there are key contributions to be made toward understanding biogeochemical cycles, dynamics and function of natural ecosystems and the management of agricultural systems.

Nitrate accumulation and leaching potential reduced by coupled water and nitrogen management in the Huang-Huai-Hai Plain

Irrigation and nitrogen (N) fertilization in excess of crop requirements are responsible for substantial nitrate accumulation in the soil profile and contamination of groundwater by nitrate leaching during intensive agricultural production. In this on-farm field trial, we compared 16 different water and N treatments on nitrate accumulation and its distribution in the soil profile (0-180cm), nitrate leaching potential, and groundwater nitrate concentration within a summer-maize (Zea mays L.) and winter-wheat (Triticum aestivum L.) rotation system in the Huang-Huai-Hai Plain over five cropping cycles (2006-2010). The results indicated that nitrate remaining in the soil profile after crop harvest and nitrate concentration of soil solutions at two depths (80cm and 180cm) declined with increasing irrigation amounts and increased greatly with increasing N application rates, especially for seasonal N application rates higher than 190kgNha-1. During the experimental period, continuous torrential rainfall was the main cause for nitrate leaching beyond the root zone (180cm), which could pose potential risks for contamination of groundwater. Nitrate concentration of groundwater varied from 0.2 to 2.9mgL-1, which was lower than the limit of 10mgL-1 as the maximum safe level for drinking water. In view of the balance between grain production and environmental consequences, seasonal N application rates of 190kgNha-1 and 150kgNha-1 were recommended for winter wheat and summer maize, respectively. Irrigation to the field capacity of 0-40cm and 0-60cm soil depth could be appropriate for maize and wheat, respectively. Therefore, taking grain yields, mineral N accumulation in the soil profile, nitrate leaching potential, and groundwater quality into account, coupled water and N management could provide an opportunity to promote grain production while reducing negative environmental impacts in this region.

New methodology for soil aggregate fractionation to investigate phosphorus transformations in iron oxide-rich tropical agricultural soil

Summary Understanding phosphorus (P) dynamics at the soil aggregate level is necessary to increase P-use efficiency and for reducing reliance on external P inputs. Traditional methods of soil fractionation are often unsuitable for the study of P dynamics within soil aggregates of tropical soil because of the large amounts of strongly P-sorbing iron oxide concretions. Here, we present an alternative method of soil fractionation to assess carbon (C), nitrogen (N) and P cycling in a very weathered tropical soil (total P, 883 ± 19 mg P kg−1) rich in iron concretions (total P, 1136 ± 28 mg P kg−1). This wet-sieving method removes large iron concretions (> 2000 µm) without any marked effect on smaller soil aggregates, which reduces the error associated with overestimation of aggregation. It reduces variation in nutrient content within larger soil aggregates, and also enables nutrient cycling within water-stable soil aggregates to be studied. In addition, because it uses field-moist soil it is possible to measure microbial biomass, community structure, or both, within aggregate fractions. Although this method is important for measuring and understanding C, N and P dynamics within soil aggregate fractions, both the nutrient content and biochemical characteristics of the iron concretions need to be considered to obtain a deeper understanding of nutrient dynamics within the whole soil. Highlights An aggregate fractionation method for tropical soil rich in iron concretions. This method can separate large iron concretions from soil aggregates. Error and variation in aggregation measurements and associated nutrient concentrations are reduced. Measurement of P in concretions and aggregates separately provides a better understanding of P dynamics.

Correction to: Organic phosphorus in the terrestrial environment: a perspective on the state of the art and future priorities

The article “Organic phosphorus in the terrestrial environment: a perspective on the state of the art and future priorities”, written by Timothy S George et al., was originally published with incorrect affiliation information for one of the co-authors, E. Klumpp.