Soil magnesium (Mg) deficiency is a common problem in many crop plants including rapeseed (Brassica napus L.), resulting in significant impairments in seed yield and quality. However, precise application approaches and technologies used for Mg fertilization are still not well established for rapeseed plants grown under field conditions. A better understanding and characterization of the relationship between soil Mg supply and yield response of plants is of great importance for appropriate Mg fertilization management. This study used large-scale experiments to (i) establish a criterion for soil extractable Mg (ex-Mg) in rapeseed-cultivated soils, (ii) evaluate the role of Mg in improving rapeseed yield and quality under contrasting soil ex-Mg status and (iii) optimize Mg fertilization programs based on native soil Mg supply. A large-scale field study program comprising of 56 rapeseed field trials, each with five Mg application levels (0, 9, 18, 27, 36 kg Mg ha−1), was conducted in 13 provinces of China to investigate the effects of soil Mg status on rapeseed yield and quality. A soil ex-Mg criteria system was established to optimize Mg fertilization of rapeseed plants based on yield responses and soil ex-Mg levels. The critical soil ex-Mg for rapeseed was found to be 200 mg kg−1, and seed yield was increased by more than 5 % after adding Mg fertilizers in over 85 % of the experimental trials. In case of severe Mg deficiency (ex-Mg < 70 mg kg−1), Mg fertilization improved seed yield by about 40 % and this increase was closely related to the number of pods per plant and seeds per pod. When soil ex-Mg concentration was above 70 mg kg−1, the increments of seed yield by Mg fertilization were diminished. Magnesium fertilization also improved seed oil and oleic acid concentrations of plants grown on severe Mg-depleted soils. The average recommended Mg rate was 23.2 kg Mg ha−1 under severe soil Mg deficiency conditions, which then showed decreases as the soil ex-Mg increases. Besides soil ex-Mg, soil pH, the soil Ca2+ and K+ concentrations as well as the yield capacity of plants were further factors affecting the agronomic effectiveness of Mg fertilization on crop yield and Mg application rates. For example, seed yield significantly increased in response to Mg fertilization under high soil K/Mg (>2) and Ca/Mg (>20) ratios. The results collected from 56 field experiments indicate that soil ex-Mg level is a critical factor in determining Mg application rates in rapeseed-cultivated soils, and represents an important factor involved in varied response of rapeseed plants in respect to seed yield and quality. The study highlights the significance of soil ex-Mg levels and optimization of Mg recommendations in achieving improvements in seed yield and quality of rapeseed plants grown under diverse native ex-Mg levels.
Agricultural and livestock production cover more than a third of the Earth's land surface and are crucial to food supply. Soil extracellular enzymes play an important role in the transformation of elements and compounds in soil, particularly acid (ACP) and alkaline (ALP) phosphatases (both, APases). These enzymes have a vital role in releasing phosphorus (P) from organic matter. However, the effect of climate variables and agro-ecosystem management on APase activity in croplands remains unclear, as does its eventual relationship with agricultural productivity. Therefore, we compiled a global database of APase activity in croplands (between 1977 and 2022) and we analysed 5876 observations across 474 papers to study climate variables, crop family, and management effects on ACP and ALP activity, and their relationship with yield. ACP activity is reduced by higher temperatures (p<0.001) and lower rainfall (p=0.002). There was an interaction effect of temperature and precipitation on ALP activity (p=0.046), with the negative effect of temperature being stronger with high precipitation, and low precipitation showing low ALP activity levels at any temperature. The crop family greatly influenced APase activity (p<0.001). Management practices affected ACP and ALP activity differently; ACP activity was positively influenced by organic fertilization combined with, crop rotation or irrigation by an average of 15.6 % and 30.7 %, respectively. ALP activity was mainly positively influenced by the interaction of two different factors: organic or inorganic-organic fertilization and reduced or zero tillage. Further understanding of soil enzyme mechanisms would aid global food security and yield. As ACP activity doubles from 100.0 to 200.0 mg pNP kg−1h−1, the crop yield increases by more than two-fold, an outcome not demonstrated in croplands until now. These results could enhance yield potential through the promotion of APase activity, and the consideration of climate variables and agro-ecosystem management, which could ultimately improve cost-benefit ratios for sustainable crop growth.
To ensure the sustainable use of phosphorus (P) fertilizers it is necessary to develop P management strategies that maximize crop yield while minimizing P leaching. Current P management practices, based on single agronomic soil P tests such as Olsen P (POLSEN), do not consider the P sorption capacity allowing one to predict soil P dynamics in response to long-term P inputs and related impacts on crop yield, P uptake and P loss. The oxalate extraction method, measuring contents of P, aluminium (Al) and iron (Fe), has been identified as a high-potential agri-environmental P test as it measures the reversibly sorbed P pool. This test gives insights in the plant-available P pool, the P sorption capacity and the degree of P Saturation (PSD). In this study, we evaluated the performance of POLSEN and PSD in explaining crop yield and P leaching risks, using long-term field experiments from China (n = 1) and Europe (n = 11), and we applied these insights to an inventory dataset (grid-sampling based) of Qiyang county in China. The variations in crop yield and P leaching risk were better explained by PSD (R2=0.5–0.95 for crop yield and 0.84–0.95 for P leaching risk) than by POLSEN (R2=0.68–0.93 for crop yield and < 0.73 for P leaching risk). The PSD target level to achieve 90 % of the potential yield was higher than the critical level to avoid enhanced P leaching for the Chinese but not for the European experiments. When applied on regional scale, we showed that the use of POLSEN might underestimate P demand for crop production and overestimate the potential leaching risk. Considering the theoretical advantages of PSD as a combined agri-environmental soil P test, we discussed the implications of its use for regional P management and showed that the α value, which is used to estimate PSD from oxalate extractable Al and Fe, needs to be adjusted for regional pedogenic and related climate factors.
This research paper presents a comprehensive scientometric analysis of English articles from the Scopus database regarding the topic of cover crop management from 1956 to March 2024. Through the analysis of the annual production trend, total production, a co-occurrence network of keywords, co-authorship networks, and co-citation networks, the data was mapped and visualized using VOSviewer and Bibliometrix software. There was an exponential increase in publications from 1991 onwards. The predominant subject was Agricultural and Biological Sciences and the most relevant journals, authors, and documents were related to this topic. Additionally, the most productive country was the United States, but in terms of article production per surface area, other countries, such as Switzerland and The Netherlands, evidence the great weight of cover crop management in these countries. The identified research topics were related to the application of different crops as cover crops and the effects on different cultivars, also soil quality improvement, and fertilization and nutrient efficiency. An emerging research topic was found to be the usefulness of cover crops as effective tools for climate change adaptation and mitigation strategies in agriculture. Future research in the field of cover crop management could be directed towards climate-adaptive cover crop species and varieties, the use of technological innovations for cover crop monitoring, and management and analysis of the economic and social impacts of cover crop adoption.