RESUMO
Soil texture plays a crucial role in organic matter (OM) mineralization through both direct interactions with minerals and indirect effects on soil moisture. Separating these effects could enhance the modelling of soil organic carbon (SOC) dynamics under climate change scenarios. However, the attempts have been limited small-scale experiments. Here, we studied the effects of soil texture on added OM mineralization in loamy sand, loam and silt loam soils in nine agricultural fields in Flanders, Belgium. Soil moisture, temperature, groundwater table depth and the mineralization of 13C-labeled ryegrass were monitored in buried mesocosms for approximately three months during a dry summer. Ryegrass-C mineralization was lowest in the loamy sand (39 ± 7 %) followed by silt loam (48 ± 7 %) and loam (63 ± 5 %) soils, challenging the current clay%-based moderation of C-mineralization rates in soil models. Soil temperature was not influenced by soil texture, whereas soil moisture was indeed dependent on soil texture. It appears that capillarity sustained upward water supply from groundwater to the topsoil in loam and silt loam soils but not in loamy sand soil, although this difference in capillary rise could not fully explain the higher moisture content in loam than that in silt loam soils. Additionally, soil texture only impacted remnant added ryegrass pieces (>500 µm) but not the finer ryegrass-derived SOC (<500 µm), which might point at the important indirect control of texture on OM mineralization during prolonged summer drought. However, these effects are only manifested during drought when no other factors (e.g., groundwater depth or subsurface water flows) exert an overriding impact on the soil water balance. Overall, our findings highlight the need to properly incorporate the indirect effects of soil texture on OM mineralization into soil carbon models to accurately predict soil C stocks under future climate change scenarios.
RESUMO
Introduction: Over the last decade, there has been a growing interest in cereal-legume intercropping for sustainable agriculture. As a result numerous papers, including reviews, focus on this topic. Screening this large amount of papers, to identify knowledge gaps and future research opportunities, manually, would be a complex and time consuming task. Materials and methods: Bibliometric analysis combined with text mining and topic modelling, to automatically find topics and to derive a representation of intercropping papers as a potential solution to reduce the workload was tested. Both common (e.g. wheat and soybean) as well as underutilized crops (e.g. buckwheat, lupin, triticale) were the focus of this study. The corpus used for the analysis was retrieved from Web of Science and Scopus on 5th September 2022 and consisted of 4,732 papers. Results: The number of papers on cereal-legume intercropping increased in recent years, with most studies being located in China. Literature mainly dealt with the cereals maize and wheat and the legume soybean whereas buckwheat and lupin received little attention from academic researchers. These underutilized crops are certainly interesting to be used as intercropping partners, however, additional research on optimization of management and cultivar's choice is important. Yield and nitrogen fixation are the most commonly studied traits in cereal-legume intercropping. Last decade, there is an increasing interest in climate resilience, sustainability and biodiversity. Also the term "ecosystem services" came into play, but still with a low frequency. The regulating services and provisioning services seem to be the most studied, in contrast terms related to potential cultural services were not encountered. Discussion: In conclusion, based on this review several research opportunities were identified. Minor crops like lupin and buckwheat need to be evaluated for their role as intercropping partners. The interaction between species based on e.g. root exudates needs to be further unraveled. Also diseases, pests and weeds in relation to intercropping deserve more attention and finally more in-depth research on the additional benefits/ecosystem services associated with intercropping systems is necessary.
RESUMO
Yield losses of crops due to plant pathogens are a major threat in all agricultural systems. In view of environmental issues and legislative limitations for chemical crop protection products, the need to design new environmentally friendly disease management strategies has gained interest. Despite the unique capability of green leaf volatiles (GLVs) to suppress a broad spectrum of plant pathogens, their capacity to control the potato late-blight-causing agent Phytophthora infestans has not been well studied. This study addresses the potential role of the GLV Z-3-hexenyl acetate (Z-3-HAC) in decreasing the severity of late blight and the underlying gene-based evidence leading to this effect. Nine-week-old potato plants (Solanum tuberosum L.) were exposed to Z-3-HAC before they were inoculated with P. infestans genotypes at different time points. These pre-exposed potato plants exhibited slower disease development after infection with the highly pathogenic genotype of P. infestans (EU-13-A2) over time. Qualitative assessment showed that the exposed, infected plants possessed significantly lower sporulation intensity and disease severity compared to the control plants. Hypersensitive response (HR)-like symptoms were observed on the treated leaves when inoculated with different pathogen genotypes. No HR-like lesions were detected on the untreated leaves after infection. It was shown that the transcript levels of several defense-related genes, especially those that are involved in reactive oxygen species (ROS) production pathways were significantly expressed in plants at 48 and 72 h postexposure to the Z-3-HAC. The current work provides evidence on the role of Z-3-HAC in the increased protection of potato plants against late blight through plant immunity and offers new opportunities for the sustainable control of potato diseases.