Aims
This study aimed to investigate the effects of coexistence with faba bean, a phosphorus (P)-efficient crop, on soil-accumulated P use by a maize/faba bean intercropping system on dynamic changes ...in soil P pool.
Methods
Maize and faba bean were grown in P-accumulated soil as either sole cropping or intercropping. After one year (Stage I) or four years (Stage II) of no P application, soil samples were collected respectively and analyzed for soil P pools using sequential fractionation. Aboveground biomass and P content were annually measured from 2013 to 2016 to assess the annual P balance.
Results
The intercropped maize/faba bean system showed a P-uptake advantage, with a Land Equivalent Ratio (LER) ranging from 1.2 to 1.5. The average shoot P content over the four years in intercropped maize and faba bean was significantly greater than that of the corresponding sole crops by 29% and 30%, respectively. Over the three-year P depletion period, the three cropping systems primarily depleted the 1 M HCl-P
i
fraction, followed by sole maize, which depleted the NaOH-P
i
and concentrated HCl-P
o
fractions. Sole faba bean depleted the alkali-soluble P
o
fraction (extracted by NaHCO
3
and NaOH), and the intercropped maize/faba bean system depleted the conc. HCl-P
o
fraction, which was similar to the effect of sole maize.
Conclusions
Both sole crops and intercrops mainly depleted 1 M HCl-P
i
, but differed in P
o
depletion. Sole maize and maize/faba bean intercropping depleted the sparingly labile P
o
fraction, while sole faba bean depleted the labile and moderately labile P
o
fractions.
Arbuscular mycorrhizal fungi (AMF) transfer plant photosynthate underground which can stimulate soil microbial growth. In this study, we examined whether there was a potential link between carbon (C) ...release from an AMF and phosphorus (P) availability via a phosphatesolubilizing bacterium (PSB).
We investigated the outcome of the interaction between the AMF and the PSB by conducting a microcosm and two Petri plate experiments. An in vitro culture experiment was also conducted to determine the direct impact of AMF hyphal exudates on growth of the PSB.
The AMF released substantial C to the environment, triggering PSB growth and activity. In return, the PSB enhanced mineralization of organic P, increasing P availability for the AMF. When soil available P was low, the PSB competed with the AMF for P, and its activity was not stimulated by the fungus. When additional P was added to increase soil available P, the PSB enhanced AMF hyphal growth, and PSB activity was also stimulated by the fungus.
Our results suggest that an AMF and a free-living PSB interacted to the benefit of each other by providing the C or P that the other microorganism required, but these interactions depended upon background P availability.
Plants and humans cannot easily acquire iron from their nutrient sources although it is abundant in nature. Thus, iron deficiency is one of the major limiting factors affecting crop yields, food ...quality and human nutrition. Therefore, approaches need to be developed to increase Fe uptake by roots, transfer to edible plant portions and absorption by humans from plant food sources. Integrated strategies for soil and crop management are attractive not only for improving growing conditions for crops but also for exploiting a plant's potential for Fe mobilization and utilization. Recent research progress in soil and crop management has provided the means to resolve complex plant Fe nutritional problems through manipulating the rhizosphere (e.g., rhizosphere fertilization and water regulation), and crop management (includes managing cropping systems and screening for Fe efficient species and varieties). Some simple and effective soil management practices, termed ‘rhizosphere fertilization' (such as root feeding and bag fertilization) have been developed and widely used by local farmers in China to improve the Fe nutrition of fruit plants. Production practices for rice cultivation are shifting from paddy-rice to aerobic rice to make more efficient use of irrigation water. This shift has brought about increases in Fe deficiency in rice, a new challenge depressing iron availability in rice and reducing Fe supplies to humans. Current crop management strategies addressing Fe deficiency include Fe foliar application, trunk injection, plant breeding for enriched Fe crop species and varieties, and selection of cropping systems. Managing cropping systems, such as intercropping strategies may have numerous advantages in terms of increasing Fe availability to plants. Studies of intercropping systems on peanut/maize, wheat/chickpea and guava/sorghum or -maize increased Fe content of crops and their seed, which suggests that a reasonable intercropping system of iron-efficient species could prevent or mitigate Fe deficiency in Fe-inefficient plants. This review provides a comprehensive comparison of the strategies that have been developed to address Fe deficiency and discusses the most recent advance in soil and crop management to improve the Fe nutrition of crops. These proofs of concept studies will serve as the basis for future Fe research and for integrated and optimized management strategies to alleviate Fe deficiency in farmers' fields.
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.
•Published data on WUE of dryland maize in the Loess Plateau were analyzed.•The highest yield and WUE were under plastic mulching and the lowest in conventional practice.•The attainable WUE was ...40kgha−1mm−1 in the region.•The yield-ET relationship indicated that yield was limited by weather and management factors.•Mulching, cultivar selection, and canopy management need to be integrated for increasing WUE.
Owing to the critical situation of water resources and demographic pressure, improvement of crop water use efficiency (WUE=grain yield per unit seasonal evapotranspiration) in the dryland area of Loess Plateau of China is crucial. The aims of this study were (i) quantifying WUE of dryland maize (Zea mays L.) in the Loess Plateau, and (ii) identifying management practices that improve both WUE and yield. We compiled a data base of 36 sets of experiments spanning more than 20 years, where conventional practice (CT) was compared with alternatives including RT/NT, reduced or no tillage without straw mulching; SM, straw mulching; PM, plastic film mulching 100%; RM, plastic film mulching 50% or more; RMS, ridge mulched with plastic film+furrow mulched with crop straw.
Yield ranged from 1.12 to 14.6Mgha−1 and WUE from 2.8 to 39.0kgha−1mm−1; the maximum yield and WUE were achieved under RM, PM and RMS and the minimum under CT. Practices had small and inconsistent effect on seasonal evapotranspiration, hence variation in yield and WUE were attributable to changes in both the contribution of soil evaporation to total evapotranspiration and the partitioning of seasonal water use before and after silking. The yield-evapotranspiration relationship indicated that attainable WUE was 40kgha−1mm−1. Few crops, however, reached this efficiency emphasizing the opportunities for improvement. Implications for crop management and further improvement in yield and WUE are discussed.
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.
•Atmospheric N deposition in China was evaluated by two time-scale deposition databases.•Bulk and dry N deposition reached a peak between 2000 and 2010 and then began a steady decline.•Significant ...decrease of oxidized N deposition proved the effectiveness of NOx emissions control.•Increase of NH3 dry deposition highlighted the importance of regional NH3 mitigation.
China has experienced a dramatic change in atmospheric reactive nitrogen (Nr) emissions over the past four decades. However, it remains unclear how nitrogen (N) deposition has responded to increases and/or decreases in Nr emissions. This study quantitatively assesses temporal and spatial variations in measurements of bulk and calculated dry N deposition in China from 1980 to 2018. A long-term database (1980–2018) shows that bulk N deposition peaked in around 2000, and had declined by 45% by 2016–2018. Recent bulk and dry N deposition (based on monitoring from 2011 to 2018) decreased from 2011 to 2018, with current average values of 19.4 ± 0.8 and 20.6 ± 0.4 kg N ha−1 yr−1, respectively. Oxidized N deposition, especially dry deposition, decreased after 2010 due to NOx emission controls. In contrast, reduced N deposition was approximately constant, with reductions in bulk NH4+-N deposition offset by a continuous increase in dry NH3 deposition. Elevated NH3 concentrations were found at nationwide monitoring sites even at urban sites, suggesting a strong influence of both agricultural and non-agricultural sources. Current emission controls are reducing Nr emissions and deposition but further mitigation measures are needed, especially of NH3, built on broader regional emission control strategies.
Intercropping, the simultaneous production of multiple crops on the same field, provides opportunities for the sustainable intensification of agriculture if it can provide a greater yield per unit ...land and fertilizer than sole crops. The worldwide absolute yield gain of intercropping as compared with sole crops has not been analysed. We therefore performed a global meta-analysis to quantify the effect of intercropping on the yield gain, exploring the effects of crop species combinations, temporal and spatial arrangements, and fertilizer input. We found that the absolute yield gains, compared with monocultures, were the greatest for mixtures of maize with short-grain cereals or legumes that had substantial temporal niche differentiation from maize, when grown with high nutrient inputs, and using multirow strips of each species. This approach, commonly practised in China, provided yield gains that were (in an absolute sense) about four times as large as those in another, low-input intercropping strategy, commonly practised outside China. The alternative intercropping strategy consisted of growing mixtures of short-stature crop species, often as full mixtures, with the same growing period and with low to moderate nutrient inputs. Both the low- and high-yield intercropping strategies saved 16-29% of the land and 19-36% of the fertilizer compared with monocultures grown under the same management as the intercrop. The two syndromes of production in intercropping uncovered by this meta-analysis show that intercropping offers opportunities for the sustainable intensification of both high- and low-input agriculture.
Magnesium (Mg) affects various critical physiological and biochemical processes in higher plants, and its deficiency impedes plant growth and development. Although potassium (K)-induced Mg deficiency ...in agricultural production is widespread, the specific relationship of K with Mg and especially its competitive nature is poorly understood. This review summarizes current knowledge on the interactions between K and Mg with respect to their root uptake, root-to-shoot translocation and distribution in plants. Their synergistic effects on certain physiological functions are also described. The antagonistic effect of K on Mg is stronger than that of Mg on K in root absorption and transport within plants, indicating that the balanced use of K and Mg fertilizers is necessary for sustaining high plant-available Mg and alleviating K-induced Mg deficiency, especially in plant species with high K demand or in high-available-K soil. The relationship between Mg and K in plant tissues may be antagonistic or synergistic depending on plant species, cell type, leaf age, source- and sink organs. There are synergistic effects of K and Mg on photosynthesis, carbohydrate transport and allocation, nitrogen metabolism, and turgor regulation. Definition of optimal K/Mg ratios for soils and plant tissues is desirable for maintaining proper nutritional status in plants, leading to a physiological state supporting crop production. Future research should concentrate on identifying the physiological and molecular mechanisms underlying the interactions between K and Mg in a given physiological function.
China has been seriously affected by particulate matter (PM) and gaseous pollutants in the atmosphere. In this study, we systematically analyse the spatio-temporal patterns of PM2.5, PM10, SO2, CO, ...NO2, and O3 and the associated health risks, using data collected from 1498 national air quality monitoring sites. An analysis of the averaged data from all the sites indicated that, from 2015 to 2018, annual mean concentrations of PM2.5, PM10, SO2 and CO declined by 3.2 μg m−3, 3.7 μg m−3, 3.9 μg m−3, and 0.1 mg m−3, respectively. In contrast, those of NO2 and O3 increased at rates of 0.4 and 3.1 μg m−3, respectively. Except for O3, the annual mean concentrations of all pollutants were generally the highest in North China and lowest in the Tibetan Plateau. The concentrations were generally higher in the north of the country than in the south. In all regions of China, the pollutant concentrations were the highest in winter and lowest in summer, except for O3, which showed an opposite seasonal pattern. Overall, the seasonal mean concentrations of all the pollutants (except for O3) significantly decreased between the same seasons in 2018 and 2015, whereas the seasonal mean O3 concentrations generally significantly increased, and/or remained at stable levels in all four seasons except for winter. Diurnal variations of all pollutants (except for O3) exhibited a bimodal pattern with peaks between 8:00 and 11:00 a.m. and 9:00 and 12:00 p.m., whereas O3 exhibited a unimodal pattern with maximum values between 5:00 and 7:00 p.m. No significant differences in the daily mean concentrations of all pollutants were found between weekdays and weekends in all regions, except for PM2.5 and PM10 in Northeast China. In Northwest China and Southeast China, PM2.5 showed stronger correlations with NO2 relative to SO2, suggesting that NOx emission control may be more effective than SO2 emission control for alleviating PM2.5 formation. Compared with 2015, the total PM2.5-attributable mortality, number of respiratory and cardiovascular diseases, and incidence of chronic bronchitis decreased overall by 23.4%–26.9% in 2018. In contrast, for O3-attributable deaths, there was an increase of 18.9%. Our study not only improves the understanding of the spatial and temporal patterns of air pollutants in China, but also highlights that synchronous control of PM2.5 and O3 pollution should be implemented to achieve dual benefits in protecting human health.
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•Hourly concentrations of six air pollutants were analysed at1498 sites in China.•Except O3 and NO2, all the pollutants concentrations decreased annually.•O3 peaked in the Tibetan Plateau, whereas the other pollutants in North China.•The diurnal variations of all pollutants displayed a bimodal pattern except for O3.•O3 pollution should be reduced to maximise the protection of human health.
Our study highlights the large variability in the spatial and temporal patterns of air pollutants over China and indicates that O3 pollution should be given greater consideration.
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