Background and aims Alterations in root growth and rhizosphere processes in maize (Zea mays L.) occur under phosphorus (P) deficiency, but the dynamics of root morphological and physiological ...modifications with increasing shoot P concentration remain unclear. This study investigated root responses to a wide gradient in shoot P status. Methods A range of maize shoot P concentrations (1.0–4.0 mg g−1) was established using controlled pot experiment with eleven rates of P supply from 0 to 1200 mg P kg−1 soil. Root morphology and rhizosphere processes were characterized 28 days after planting. Results Maize reached maximum biomass at shoot P concentration of 2.7 mg g−1. Root morphological responses (i.e. total root length, specific root length and proportion of fine roots) showed a strong increasing trend with decreasing shoot P concentration (1.1–1.3 mg g−1), but they decreased when shoot P concentration was extremely low (below 1.1 mg g−1). In contrast, with increasing shoot P concentration, root morphological responses decreased, but root physiological responses (rhizosphere acidification, acid phosphatase activity and carboxylate exudation in the rhizosphere) were enhanced, and no decrease was noted even at high shoot P concentration (4.0 mg g−1) corresponding to excess P supply. Conclusions Increasing maize shoot P concentration induced a decrease in root morphological responses and an enhancement in root exudation, with maize response to P deficiency being dependent on root morphological rather than physiological traits.
• Plant roots exhibit diverse root functional traits to enable soil phosphorus (P) acquisition, including changes in root morphology, root exudation and mycorrhizal symbioses. Yet, whether these ...traits are differently coordinated among crop species to enhance P acquisition is unclear.
• Here, eight root functional traits for P acquisition were characterized in 16 major herbaceous crop species grown in a glasshouse under limiting and adequate soil P availability.
• We found substantial interspecific variation in root functional traits among species. Those with thinner roots showed more root branching and less first-order root length, and had consistently lower colonization by arbuscular mycorrhizal fungi (AMF), fewer rhizosheath carboxylates and reduced acid phosphatase activity. In response to limiting soil P, species with thinner roots showed a stronger response in root branching, first-order root length and specific root length of the whole root system, Conversely, species with thicker roots exhibited higher colonization by AMF and/or more P-mobilizing exudates in the rhizosheath.
• We conclude that, at the species level, tradeoffs occur among the three groups of root functional traits we examined. Root diameter is a good predictor of the relative expression of these traits and how they change when P is limiting.
Aims
Intercropping cereals with legumes may achieve high crop yields at reduced input levels. Several studies have indicated that intercropping increases phosphorus use efficiency but no overarching ...analysis exists on the role of species traits and input levels. Here we synthesize the available information on P use efficiency in cereal/legume intercropping.
Methods
Global data on yields, P uptake and nutrient input in cereal/legume mixtures were extracted from the literature and statistically analyzed. Co-variables explaining P uptake efficiency and yield were considered.
Results
P uptake was substantially increased with an average value of LER
P
, the land equivalent ratio for P uptake, of 1.24, and an average NE
P
(observed P uptake minus expected P uptake) of 3.67 kg P ha
−1
. The conversion efficiency of P uptake to biomass decreased with P uptake and was lower in intercrops than in sole crops but the conversion efficiency to yield was not affected by intercropping. The P fertilizer requirement was 21% lower in intercrops than in sole crops for the same yields.
Conclusions
Substantial improvements in land use efficiency and P uptake are obtained by cereal/legume intercropping. Cereal/legume intercropping has therefore potential to increase P fertilizer use efficiency in agriculture.
Due to the increasing environmental impact of food production, carbon footprint as an indicator can guide farmland management. This study established a method and estimated the carbon footprint of ...grain production in China based on life cycle analysis (LCA). The results showed that grain production has a high carbon footprint in 2013, i.e., 4052 kg ce/ha or 0.48 kg ce/kg for maize, 5455 kg ce/ha or 0.75 kg ce/kg for wheat and 11881 kg ce/ha or 1.60 kg ce/kg for rice. These footprints are higher than that of other countries, such as the United States, Canada and India. The most important factors governing carbon emissions were the application of nitrogen fertiliser (8-49%), straw burning (0-70%), energy consumption by machinery (6-40%), energy consumption for irrigation (0-44%) and CH
emissions from rice paddies (15-73%). The most important carbon sequestration factors included returning of crop straw (41-90%), chemical nitrogen fertiliser application (10-59%) and no-till farming practices (0-10%). Different factors dominated in different crop systems in different regions. To identity site-specific key factors and take countermeasures could significantly lower carbon footprint, e.g., ban straw burning in northeast and south China, stopping continuous flooding irrigation in wheat and rice production system.
Phosphorus (P) is one of the major factors worldwide limiting crop growth. Enhancing P efficiency in plants can be achieved through improving P acquisition, utilization, or both. Which of these ...approaches is more critical for enhancing P efficiency in crops, particularly in intensive cropping systems? P availability is unevenly distributed through the soil profile. Most modern crop cultivars are selected through conventional breeding approaches for better adaptation to stratified soil P by root architectural and morphological traits that allow for more P acquisition from the P-rich soil surface zone. Conversely, most crops have relatively efficient P uptake capacity but low P translocation and remobilization. Hence, phosphorus utilization efficiency (PUE) becomes a significant bottleneck for further improvements in crop P efficiency. Furthermore, the modification of root systems requires additional carbon input, and thus crops might sacrifice carbohydrates for higher yield to meet demand for P acquisition. With the support from soybean transformation studies, we speculate that enhancement of PUE might become a potentially powerful strategy for increasing P efficiency in modern crops grown in intensive cropping systems.
Root and rhizosphere research has been conducted for many decades, but the underlying strategy of root/rhizosphere processes and management in intensive cropping systems remain largely to be ...determined. Improved grain production to meet the food demand of an increasing population has been highly dependent on chemical fertilizer input based on the traditionally assumed notion of ‘high input, high output’, which results in overuse of fertilizers but ignores the biological potential of roots or rhizosphere for efficient mobilization and acquisition of soil nutrients. Root exploration in soil nutrient resources and root-induced rhizosphere processes plays an important role in controlling nutrient transformation, efficient nutrient acquisition and use, and thus crop productivity. The efficiency of root/rhizosphere in terms of improved nutrient mobilization, acquisition, and use can be fully exploited by: (1) manipulating root growth (i.e. root development and size, root system architecture, and distribution); (2) regulating rhizosphere processes (i.e. rhizosphere acidification, organic anion and acid phosphatase exudation, localized application of nutrients, rhizosphere interactions, and use of efficient crop genotypes); and (3) optimizing root zone management to synchronize root growth and soil nutrient supply with demand of nutrients in cropping systems. Experiments have shown that root/rhizosphere management is an effective approach to increase both nutrient use efficiency and crop productivity for sustainable crop production. The objectives of this paper are to summarize the principles of root/rhizosphere management and provide an overview of some successful case studies on how to exploit the biological potential of root system and rhizosphere processes to improve crop productivity and nutrient use efficiency.
College students' mental health has been seriously impacted during the global COVID-19 lockdown. There is evidence that dispositional mindfulness is beneficial to mental health. However, few studies ...have looked at the relationship between dispositional mindfulness and mental health from the standpoint of self-compassion. Furthermore, it is unclear under what circumstances dispositional mindfulness is linked to mental health during COVID-19 lockdown. To fill this gap, the current study investigated self-compassion as a possible mediating factor and gender as a possible moderating effect between dispositional mindfulness and mental health. The sample included 1,018 Chinese university students during the COVID-19 lockdown (M age = 20.12; SD age = 1.17) who had completed self-report questionnaires on dispositional mindfulness, self-compassion, and mental health. According to the findings of mediation analysis, self-compassion partially mediated the relationship between dispositional mindfulness and mental health. The moderating analysis also revealed significant moderating effects of dispositional mindfulness, self-compassion, and mental health. Male college students' mental health was significantly better protected, and the buffering effects of dispositional mindfulness and self-compassion on their mental health were significantly stronger than those of female college students. These findings advance our understanding of the process and mechanism between dispositional mindfulness and mental health, broadened and deepened the understanding of the relationship between dispositional mindfulness and mental health, as well as the mediating role of self-compassion and the moderating role of gender, and offer practical guidance for improving college students' mental health during the COVID-19 lockdown.
In recent years, agricultural growth in China has accelerated remarkably, but most of this growth has been driven by increased yield per unit area rather than by expansion of the cultivated area. ...Looking towards 2030, to meet the demand for grain and to feed a growing population on the available arable land, it is suggested that annual crop production should be increased to around 580 Mt and that yield should increase by at least 2% annually. Crop production will become more difficult with climate change, resource scarcity (e.g. land, water, energy, and nutrients) and environmental degradation (e.g. declining soil quality, increased greenhouse gas emissions, and surface water eutrophication). To pursue the fastest and most practical route to improved yield, the near-term strategy is application and extension of existing agricultural technologies. This would lead to substantial improvement in crop and soil management practices, which are currently suboptimal. Two pivotal components are required if we are to follow new trajectories. First, the disciplines of soil management and agronomy need to be given increased emphasis in research and teaching, as part of a grand food security challenge. Second, continued genetic improvement in crop varieties will be vital. However, our view is that the biggest gains from improved technology will come most immediately from combinations of improved crops and improved agronomical practices. The objectives of this paper are to summarize the historical trend of crop production in China and to examine the main constraints to the further increase of crop productivity. The paper provides a perspective on the challenge faced by science and technology in agriculture which must be met both in terms of increased crop productivity but also in increased resource use efficiency and the protection of environmental quality.
Imbalanced application of nitrogen （N） and phosphorus （P） fertilizers can result in reduced crop yield, low nutrient use efficiency, and high loss of nutrients and soil nitrate nitrogen （NO3--N） ...accumulation decreases when N is applied with P and/or manure; however, the effect of applications of N with P and/or manure on root growth and distribution in the soil profile is not fully understood. The aim of this study was to investigate the combined effects of different N and P fertilizer application rates with or without manure on maize （Zea mays L.） yield, N uptake, root growth, apparent N surplus, Olsen-P concentration, and mineral N （Nmin） accumulation in a fluvo-aquic calcareous soil from a long-term （28-year） experiment. The experiment comprised twelve combinations of chemical N and P fertilizers, either with or without chicken manure, as treatments in four replicates. The yield of maize grain was 82% higher, the N uptake 100% higher, and the Nmin accumulation 39% lower in the treatments with combined N and P in comparison to N fertilizer only. The maize root length density in the 30-60 cm layer was three times greater in the treatments with N and P fertilizers than with N fertilizer only. Manure addition increased maize yield by 50% and N uptake by 43%, and reduced Nmin （mostly NO3-N） accumulation in the soil by 46%. The long-term application of manure and P fertilizer resulted in significant increases in soil Olsen-P concentration when no N fertilizer was applied. Manure application reduced the apparent N surplus for all treatments. These results suggest that combined N and P fertilizer applications could enhance maize grain yield and nutrient uptake via stimulating root growth, leading to reduced accumulation of potentially leachable NO3-N in soil, and manure application was a practical way to improve degraded soils in China and the rest of the world.
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