Abstract The relationships among soil total C (STC), soil inorganic C (SIC), and soil organic C (SOC) stocks and crop yields in dryland cropping systems are not adequately known. We measured STC, SIC, and SOC stocks at the 0‐ to 120‐cm depth and crop yields at two dryland farming sites (Froid and Sidney, MT) after 10–11 years of crop rotations in the United States northern Great Plains. Crop rotations in Froid included rotations of durum ( Triticum turgidum L.), camelina ( Camelina ceantz L.), pea ( Pisum sativum L.), canola ( Brassica napus L.), and safflower ( Carthamaus tinctorius L.). Crop rotations in Sidney were rotations of barley ( Hordeum vulgare L.), pea, camelina, canola, and spring and winter wheat ( Triticum aestivum L.). Highly diversified crop rotations and monocropping increased SOC and STC compared to less diversified rotations, but SIC varied by crop rotation. The principal component analysis showed that STC and SOC at 0–15, 15–30, 30–60, 60–90, 90–120, and 0–120 cm were related to each other, but the relationship of SIC with STC and SOC varied by site. At Froid, SIC at 0–15 cm was related, but STC and SOC at all depths were not related to crop yield. At Sidney, SIC at 0–15, 90–120, and 0–120 cm was related to crop yield. The SOC at 30–60, 60–90, 0–30, 0–60, 0–90, and 0–120 cm was more closely related to crop yield than STC. The SOC can be used for measuring soil C sequestration and relating to crop yields in dryland cropping systems.
Abstract The application of biochar to soil has become widespread practice due to its positive effects on soil water retention and fertility. However, biochar also impacts the radiological condition of the soil environment, manifesting itself through changes in radon emanation and the concentrations of natural and anthropogenic radioactive isotopes. The aim of the study was to determine the extent to which biochar affects the concentrations of radioactive isotopes in the soil over a longer period after application. A long‐term field experiment was conducted in which two types of biochar, produced of sunflower husk and wood chip, were introduced into the soil in an arable field. Twenty‐five and 43 months after the application of the biochar, the soil was tested for its content the natural radioisotopes, that is, 40 K and 226 Ra as well as anthropogenic 137 Cs. The studies were conducted using high‐resolution gamma spectrometry with an HPGe detector. The results indicate that the presence of biochar had a long‐term effect on the concentration of 137 Cs and 40 K but had no significant effect on the content of 226 Ra. The presence of biochar caused a 16.3% decrease in 137 Cs and an 8.6% increase in 40 K concentration compared to soil without biochar. These results clearly demonstrate that the application of biochar can have a positive effect, such as reducing the concentration of 137 Cs. At the same time, due to the significant amounts of Cs and K in biochar, its application may not be neutral for the radiological state of agricultural soils.
Abstract Soils are increasingly receiving treated wastewater (TWW) to support crop production and protect natural resources. However, besides water, various inputs, such as soil nutrients (salts), organic carbon, and various contaminants of emerging concern, including antibiotics, antibiotic resistance genes, pharmaceutical compounds, heavy metals, and microplastics, can be delivered. This review aims at (a) an integrated and mechanistic synthesis of current knowledge on potential impacts of TWW irrigation on key soil nitrogen turnover processes, such as nitrogen mineralization, nitrification, denitrification, and ammonia volatilization, and their drivers, and (b) identification of key knowledge and conceptual uncertainties to support future studies. Across the synthesis, no single, uniform TWW effect emerges. In fact, outcomes are consistently conditional on several co‐factors, such as treatment level, irrigation duration, soil type, and plant species, with the latter two sometimes exerting effects exceeding those of water quality itself. TWW alters soil conditions through substrate availability, redox dynamics, soil acidity and salinity, and contaminant exposure, but the mechanistic evidence linking specific drivers to specific nitrogen‐process outcomes is itself uneven. Identified knowledge and methodological gaps suggest long‐term field studies across TWW regimes, soil types, and climates; designs capable of disentangling co‐varying drivers at field scale; and laboratory studies addressing contaminant‐specific impacts, microbial functional persistence, and potential decoupling between nitrogen and carbon dynamics, an effect already evident, though unexplored as a general phenomenon, within the reviewed literature. Overall, this review offers an integrated, system‐level framework to support the evidence‐based management of environmentally and climate‐vulnerable soils receiving reclaimed or even conventional irrigation water.
