•The maize/pea intercropping improved by integrated with no-tillage and maize plant density.•The integrated system increased the crop production by 14.5 % compared to conventional practice.•The ...integrated system was beneficial in the carbon mitigation.•High carbon emission efficiency is attributed to reduce carbon emission of maize pea co-growth stage.
High yield is a benefit of production system with high input, but usually more CO2 emitted. It is unclear whether to integrate a multi-technology in the intercropping to achieve a high-yielding, low emission, and high efficiency agricultural integrated production system. In order to assess the crop production and carbon mitigation in integrated system, a field experiment of maize/pea intercropping was performed with two tillage (no-tillage and conventional tillage) and three maize plant density (low density-45,000, medium density-60,000, and high density-75,000 plants ha−1) in the oasis irrigation area of northwestern China during the 2016–2018. We found that no-tillage improved crop production and carbon mitigation, increasing maize density was able to improve yield in maize/pea intercropping, but increased the carbon emission. From the 3-year average, the integration of no-tillage and medium plant density (NI2) effectively increased the total grain yield (GY) by 14.5 %, reduced carbon emission by 3.5 % compared to conventional tillage with low maize density (CI1). Meanwhile, this integrated system had increased carbon emission efficiency (CEE) by 16.7 % compared to the CI1. For different crop components in maize/pea intercropping, no-tillage mainly reduced the carbon emission of the maize strip, but no significant effect of pea strip by increasing the maize plant density. In addition, this integrated system also increased net primary production (NPP), net ecosystem production (NEP) and carbon sequestration potential by 17.8, 19.9 and 21.8 % compared with CI1, while had highest economic benefits (average 3.1). Therefore, maize/pea intercropping compound production pattern integrated no-tillage and medium maize plant density (NI2) should be recommended as the high-efficiency model of farming system for resources saving and reducing carbon emission in oasis irrigation area of northwest China.
•Nitrogen and growing season reduction with high density sacrificed no cotton yield.•Yield compensation contributed from a higher sink growth rate after flowering.•Sink contributed yield directly, ...with flow and source did indirectly through sink.
Cotton (Gossypium hirustum L.) as well as other crops are asking for an effective production with cost reduction and environment stewardship globally, especially in the developing countries. A new cotton planting strategy should be possible by shortening the growth season (less than six months rather than seven to eight months by late sowing and early harvesting) with low nitrogen (N) and high density. Therefore, a two-year (2018–2019) field experiment was conducted with a split plot design, two planting densities (D1, 6 plants m−2; D2, 8 plants m−2) as the main plot and three N rates (150, 180 and 210 kg ha-1 referred as N1, N2, and N3, respectively) as the subplot, to determine the effects of planting density and N rate on cotton yield and biomass accumulation. Results showed that, averaged across years, cotton yield was greater for treatment D2 as compared with that in D1, and N3 did not differ from that in N2 but was greater than that in N1. The highest lint yield (1271.2 kg ha-1) was achieved in D2N2 which no differ from that in D2N3 and D1N3. The maximal biomass (K) was achieved in treatment D2N2 (1032.4 g m−2) with the average speed (VT) of 21.2 g m−2 d-1 during the fast accumulation period, and the maximal growth rate (Rm, 20.5 g m−2 d-1) of sink during the cotton growth and development. Seedcotton yield was positively correlated (r = 0.72) to the plant biomass during flowering and boll-setting period, and the yield was contributed directly by sink with a coefficient as high as 0.70, while it was contributed indirectly by flow and source with coefficients of 0.63 and 0.59, respectively. The results suggest that N reduction is feasible due to a quicker bulk sink biomass accumulation under a higher planting density, which benefits efficient cotton production in the Yangtze River Valley, China, and areas with similar ecology.
Abstract
The size of plant organs is highly responsive to environmental conditions. The plant’s embryonic stem, or hypocotyl, displays phenotypic plasticity, in response to light and temperature. The ...hypocotyl of shade avoiding species elongates to outcompete neighboring plants and secure access to sunlight. Similar elongation occurs in high temperature. However, it is poorly understood how environmental light and temperature cues interact to effect plant growth. We found that shade combined with warm temperature produces a synergistic hypocotyl growth response that dependent on PHYTOCHROME-INTERACTING FACTOR 7 (PIF7) and auxin. This unique but agriculturally relevant scenario was almost totally independent on PIF4 activity. We show that warm temperature is sufficient to promote PIF7 DNA binding but not transcriptional activation and we demonstrate that additional, unknown factor/s must be working downstream of the phyB-PIF-auxin module. Our findings will improve the predictions of how plants will respond to increased ambient temperatures when grown at high density.
Urban tree planting has the potential to reduce urban heat island intensity and building energy consumption. However, the heterogeneity of cities makes it difficult to quantitatively assess the ...integrated impacts of tree planting and street layouts. Scaled outdoor experiments were conducted to investigate the influence of tree plantings on wind and thermal environments in two-dimensional (2D) north-south oriented street canyons with various aspect ratios (building height/street width, AR = H/W = 1, 2, 3; H = 1.2 m). The effects of tree species with similar leaf area index (C. kotoense, big crown; C. macrocarpa, small crown), tree planting densities (ρ = 1, 0.5), and arrangements (double-row, single-row) were considered.
Vegetation reduces pedestrian-level wind speed by 29%–70%. For ρ = 1 and single-row arrangement, C. kotoense (big crown) has a better shading effect and decreases wall and air temperature during the daytime by up to 9.4 °C and 1.2 °C, respectively. In contrast, C. macrocarpa (small crown) leads to a temperature increase at the pedestrian level. Moreover, C. kotoense raises the air and wall temperature of the upper urban canopy layer and increases the street albedo during the daytime because of the solar radiation reflected by trees. C. kotoense/C. macrocarpa produces the maximum daytime cooling/warming and nighttime warming of air temperature when H/W = 2 owing to its weaker convective heat transfer. When H/W = 3, the building shade dominates the shading cooling and tree cooling is less significant. When ρ = 1, double-row trees (C. kotoense) reduce wall and air temperatures by up to 10.0 °C and 1.0 °C during the daytime. However, reducing ρ from 1 to 0.5 weakens the capacity of daytime cooling by C. kotoense and the warming effect by C. macrocarpa. Our study quantifies the influence of tree planting and aspect ratios on the thermal environment, which can provide meaningful references for urban tree planting and produce high-quality validation data for numerical modeling.
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•Scaled outdoor experiments are tested for tree impacts in streets (H/W = 1–3, H = 1.2 m).•Tree plantings may reduce the pedestrian-level wind speed by 29%–70%.•Species with big crown get better cooling effect than small one in the daytime.•Tree planting density of ρ = 0.5 (less dense) produces higher T than ρ = 1 (denser).•Trees reduce (raise) air-wall T below (above) them due to solar shading/reflection.
The mechanisms regulating community composition and local dominance of trees in species-rich forests are poorly resolved, but the importance of interactions with soil microbes is increasingly ...acknowledged. Here, we show that tree seedlings that interact via root-associated fungal hyphae with soils beneath neighbouring adult trees grow faster and have greater survival than seedlings that are isolated from external fungal mycelia, but these effects are observed for species possessing ectomycorrhizas (ECM) and not arbuscular mycorrhizal (AM) fungi. Moreover, survival of naturally-regenerating AM seedlings over ten years is negatively related to the density of surrounding conspecific plants, while survival of ECM tree seedlings displays positive density dependence over this interval, and AM seedling roots contain greater abundance of pathogenic fungi than roots of ECM seedlings. Our findings show that neighbourhood interactions mediated by beneficial and pathogenic soil fungi regulate plant demography and community structure in hyperdiverse forests.
Increasing the maize planting density is considered a potential approach for increasing the grain yield in China, but there is no consensus regarding its yield-increasing effect and the influence of ...specific factors. Thus, we established a database (2721 pairs of data from 187 publications) to quantify the effects of increasing the maize planting density on the phenotypic traits and yield, to determine an appropriate maize planting density for each planting area, and to quantify the effects of environmental factors and agricultural imputs on the outcomes of increasing the planting density. We found that increasing the planting density increased the individual competition among maize plants, with negative effects on their growth, but the grain yield increased by 11.18–13.43 % due to the increased population biomass. Using the database, we found large differences in the optimal density and peak grain yield among maize planting areas, and the factors that caused these differences were analyzed based on subgroup analysis. Field management practices significantly influenced the outcomes of increasing the planting density. In particular, higher agricultural inputs (irrigation amount, and nitrogen and phosphorus application rates) enhanced the positive effect of increasing plant density on the optimal plant density and peak grain yield. In addition, the effects of increasing the planting density were significantly influenced by environmental (climate and soil) factors. When the mean annual temperature was 7–14°C and the mean annual precipitation was 400–800 mm, the yield and maximum peak yield were highest in relatively fertile (high total nitrogen, available nitrogen, and soil organic matter contents) and neutral (pH 6–8) soils. Our results highlight the need to increase the current maize planting density and provide a scientific basis for determining reasonable planting densities for different maize growing areas in China.
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•It is necessary to increase the maize planting density (PD) in China.•Increasing planting density significantly increased maize grain yield.•There were differences in the optimal planting density among maize growing-areas.•The effects of increasing the PD were influenced by environmental factors.
•Single plough passage plus ridging is sufficient to increase cassava root yield in tropical soil.•Application of fertilizer generally improved cassava root yield in southwestern Nigeria.•Weed ...control in cassava by herbicide under zero plough system cannot be recommended.
Cassava is growing in importance in Nigeria as a food and industrial crop. Current yields are low due to poor soil fertility and because farmers do not use improved germplasm, clean planting material, or improved crop management in Nigeria. To provide feasible agronomic recommendations targeting increased root yield, the effects of tillage intensity, fertilizer application, plant density and weed control were tested in 230 farmers’ fields in southwestern Nigeria over two years. In 2016, tillage treatments were zero, single and double passage with a disc plough, followed by ridging (soil shaping) versus leaving the soil flat. Fertilizer application at 75:20:90 kg ha−1 NPK was tested against a control and two plant densities (10,000 versus 12,500 ha−1) were compared. In 2017, plant density at 10,000 ha−1 and double plough were excluded, while pre- and post-emergence herbicide application versus farmer’s choice of weed control (i.e. manual weeding using hand hoe) was introduced. Cassava was harvested at 12 months after planting, and yields were recorded as fresh root mass. In 2016, double plough (15.9 Mg ha−1) had a minor advantage over single plough (14.3 Mg ha−1), while zero plough produced 12.9 Mg ha−1 (P < 0.001). Ridging increased yield significantly (P < 0.01) by 2.3 Mg ha−1 after single and zero plough, but not after double plough. Across tillage treatments, planting at 12,500 plants ha−1 and fertilizer application increased yields by 1.5 and 4.2 Mg ha−1, respectively. In 2017, ridging resulted in a yield increase of 1.7 Mg ha−1 after single plough and 5.6 Mg ha−1 after zero plough. Fertilizer application increased root yield by 2.9 Mg ha-1 across tillage treatments. The use of herbicides negatively affected cassava yields in zero plough fields, compared with manual weeding. After ploughing, yield in herbicide based and manual weed control were not different. Cassava root yield response to tillage intensity strongly varied across fields, with low-yielding fields commonly responding less frequently to tillage. We conclude that unresponsive fields require measures other than increased tillage intensity to increase cassava root yields and that cost-intensive tillage operations must be targeted to responsive fields together with fertilizer application and improved weed control.
Plant-based technologies including phytomining, phytoextraction, phytodegradation, phytostabilization and phytovolatilization have drawn much attention during the last decade. To examine the ...feasibility of these nature-based solutions to accumulate, degrade, stabilize or volatize metal(loid)s and/or organic contaminants, an increasing number of field studies have been conducted. This review critically evaluates influencing factors in phytomining and phytoremediation approaches, including contaminant concentrations, fertilizer application and chelating agent addition, planting characteristics (e.g. plant density, seeding, cropping and harvesting methods), and soil properties (e.g. salinity, soil texture and soil pH). A proper trial design will assure the robustness of the results if these factors were taken into consideration seriously. We also summarized knowledge about additives used in field trials, especially biological waste-derived amendments such as biochar, compost, sewage sludge and manure. According to the literature reviewed, controversy remains whether these amendments can promote the plant performance. In addition, the utilization of microorganisms and transgenic plants in field trials, and the associated biosafety concerns such as horizontal gene transfer were discussed. Future research should examine the ecological risks associated with phytomining and phytoremediation (e.g. the secondary migration of contaminants due to improper handling of harvested plants). It is suggested that the results of field studies should guide commercial applications of phytomining and phytoremediation.
Summary
Wheat is the most widely grown crop globally, providing 20% of all human calories and protein. Achieving step changes in genetic yield potential is crucial to ensure food security, but ...efforts are thwarted by an apparent trade‐off between grain size and number. Expansins are proteins that play important roles in plant growth by enhancing stress relaxation in the cell wall, which constrains cell expansion.
Here, we describe how targeted overexpression of an α‐expansin in early developing wheat seeds leads to a significant increase in grain size without a negative effect on grain number, resulting in a yield boost under field conditions.
The best‐performing transgenic line yielded 12.3% higher average grain weight than the control, and this translated to an increase in grain yield of 11.3% in field experiments using an agronomically appropriate plant density.
This targeted transgenic approach provides an opportunity to overcome a common bottleneck to yield improvement across many crops.
See also the Commentary on this article by Cosgrove, 230: 403‐405.
In the context of ongoing climatic warming, certain landscapes could be near a tipping point where relatively small changes to their fire regimes or their postfire forest recovery dynamics could ...bring about extensive forest loss, with associated effects on biodiversity and carbon‐cycle feedbacks to climate change. Such concerns are particularly valid in the Klamath Region of northern California and southwestern Oregon, where severe fire initially converts montane conifer forests to systems dominated by broadleaf trees and shrubs. Conifers eventually overtop the competing vegetation, but until they do, these systems could be perpetuated by a cycle of reburning. To assess the vulnerability of conifer forests to increased fire activity and altered forest recovery dynamics in a warmer, drier climate, we characterized vegetation dynamics following severe fire in nine fire years over the last three decades across the climatic aridity gradient of montane conifer forests. Postfire conifer recruitment was limited to a narrow window, with 89% of recruitment in the first 4 years, and height growth tended to decrease as the lag between the fire year and the recruitment year increased. Growth reductions at longer lags were more pronounced at drier sites, where conifers comprised a smaller portion of live woody biomass. An interaction between seed‐source availability and climatic aridity drove substantial variation in the density of regenerating conifers. With increasing climatic water deficit, higher propagule pressure (i.e., smaller patch sizes for high‐severity fire) was needed to support a given conifer seedling density, which implies that projected future increases in aridity could limit postfire regeneration across a growing portion of the landscape. Under a more severe prospective warming scenario, by the end of the century more than half of the area currently capable of supporting montane conifer forest could become subject to minimal conifer regeneration in even moderate‐sized (10s of ha) high‐severity patches.
If climate change drives increases in wildfire activity while delaying postfire forest recovery, forested landscapes such as the Klamath Mountains (NW California/SW Oregon) could be at risk of extensive forest loss. To understand the vulnerability to such changes, we evaluated three decades of vegetation dynamics following high‐severity fire across the regional aridity gradient. Conifers faced a highly competitive environment following severe fire. They comprised only a small portion of live woody biomass, and recruitment was limited primarily to the first four years. Seedlings that established later faced pronounced growth suppression, particularly on drier sites. With increasing climatic aridity, more abundant seed sources were needed to support conifer recruitment at densities sufficient to develop a new forest canopy. Under a more severe warming scenario, by the end of the century just over half of the landscape could be at risk of minimal conifer recruitment following severe fire, even in relatively small high‐severity patches.
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