Low Soil Temperatures Research Articles

Negative effect of nitrogen addition on soil respiration dependent on stand age: Evidence from a 7-year field study of larch plantations in northern China

Increasing anthropogenic nitrogen (N) deposition will affect the global carbon (C) cycle, although the mechanisms and magnitudes of its effects are not yet fully understood. Soil respiration (Rs) and its components (i.e., heterotrophic (Rh) and autotrophic (Ra) respiration) represent the largest flux of carbon dioxide (CO2) from terrestrial ecosystems to the atmosphere. However, the potentially interactive effect of N addition and stand age on Rs in forests remains unclear. We conducted a 7-year (2010–2016) field experiment in three differently-aged larch plantations (11-, 20-, and 45-year-old, representing sapling, intermediate, and mature stands) to investigate the effects of different N addition rates (control: no N addition; low-N addition, N20: 20 kg N ha−1 year−1; and high-N addition, N50: 50 kg N ha−1 year−1) on Rs. We found significant seasonal variation in Rs, Rh, and Ra, with levels highest in summer and lowest in autumn. Rs correlated strongly with soil temperature and weakly with soil moisture, and Rs, Rh, and Ra increased exponentially with soil temperature. The temperature sensitivity (Q10) of Rs was lowest in the mature stand, which suggests that it will sequester relatively more C in a warmer climate. The Q10 of Ra was higher than that of Rh, indicating that it contributed proportionally more to the total soil CO2 efflux. N addition had no significant effect on Q10. Rs in the intermediate stand was significantly lower than Rs in the sapling and mature stands, which may be due to its lower soil temperature and poorer substrate quality. N addition decreased Rs by an average of 9%, but significant effects were only observed in the sapling and intermediate stands. The negative influence of N addition on Rs was largely dependent on soil temperature, with more negative effects observed in the summer when temperatures were higher, and attributable to a reduction in either Ra in the intermediate stand or Rh in the sapling stand. We hypothesize that N limitation in the young trees was alleviated by fertilization, which decreased C allocation to roots, whereas N addition may have exerted a more negative influence on soil microbial activity in the sapling stand. In summary, our results highlight the importance of stand age in regulating the negative effects of N addition on Rs and its components, which has implications for projecting the global C–climate feedback in the future.

Optimizing yield and quality in malting barley by the governance of field cultivation conditions

This study evaluates how cultivation location, year, soil conditions and starter fertilizer interact and determine yield and quality of malting barley. Size exclusion high performance liquid chromatography (SE-HPLC) was applied to determine protein composition in mature and malted barley.The effects of starter fertilizer treatments on yield and quality of malting barley was largely hidden by the impact of growing location and cultivation year on these parameters. Here, the highest yield and the lowest grain protein concentration was found in samples cultivated on sandy soil with adequate precipitation and a relatively low soil temperature (below 15–17 °C) during grain filling. In malted grains, the general change in protein composition as related to mature grains, was a decrease in the polymerized protein fractions and an increase in the more easily extractable and smaller proteins. However, cultivation conditions impacted the changes of the protein fractions; the highest break-down rates of polymerized proteins was found for samples cultivated on sandy soil with enough precipitation and a relatively low soil temperature (below 15–17 °C) during grain filling. Thus, the sandy soil, enough precipitation and relatively low soil temperature were the most beneficial both for grain yield and for protein based quality of the malting barley.

Mulch Based No‐Tillage and Compost Effects on Nitrogen Fertility in Organic Melon

Core Ideas No‐till roller crimper was confirmed to be a suitable technology for weed management. Melon yield and quality declined under no‐till roller crimped barley. Compost application and agro‐ecological service crop cultivation showed high potential carbon sink effect. Cropping systems and varieties should be adapted to no‐till roller crimper. Agro‐ecological service crop management and compost should be combined to fit the specific local conditions. Soil fertility management in organic farming systems relies on agro‐ecological service crops (ASCs, i.e break crops, living mulch) and organic compost application. This study was conducted to determine the effect of tillage, ASC termination, and compost rates on yield and soil N fertility in organic vegetable production in Central Italy. In a long‐term organic field, in a strip plot design, barley was cultivated before melon. Two termination strategies of barley (green manure–GM, flattening by the use of a roller crimper–RC) were compared with a control without barley (FA). Three compost application rates (0, 15, and 30 Mg ha−1) were studied. While the compost rates did not show any difference among compared production parameters, the combined tillage–ASC termination strategy significantly increased melon yield in the GM compared with RC treatments, probably due to the lower soil temperature under the thick barley mulch. Soil mineral N (SMN) during the melon cycle was not a limiting factor for plant growth. Mean SMN values ranged from 22 for the 2012 RC and 36 mg kg−1 for the 2012 FA. High C and N inputs in barley treatments and high compost rates indicated an N surplus, which, in the medium–long term, could represent an N storage for subsequent crops in the rotation and potentially determine C sequestration. The results demonstrated that, to assure adequate yield, the ASC mulch based no‐tillage approach should follow the redesign of the whole cropping system, taking into account the entire suite of techniques of crop management.

The use of soil cooling for growing temperate crops under tropical climate

Global climate changes have been reported to be affecting the already stressed agricultural ecosystem, especially temperate agriculture which is highly dependent on low soil temperature for optimum growth performance. The current trends of temperate agriculture include enclosed greenhouses or hydroponics techniques, but shown to be inadequate to produce temperate crops under hot and humid weather of tropical climate. This urges the need for a more sustainable farming system which is soil cooling method as described in this study. Soil cooling system cools the soils to temperate soil temperature ranges between 14.6 and 20.1 °C providing a conducive growth condition for temperate produce. The aim of this study is to confirm the usefulness of soil cooling for growing temperate crops under tropical climate. In this study, a model temperate crop, loose leaf lettuce, was grown in an enclosed greenhouse with soil cooling system for its 3-growth cycle. Air and soil temperatures were recorded during the lettuce growth. Lettuces were evaluated in terms of weight, height, number of leaves, leaf area and root length upon each harvest cycle. Under soil cooling, lettuces showed significant difference in average weight (p < 0.05) and positive development in the roots, shoot and leaves of lettuces for its 3-growth cycle. The findings showed that soil cooling approach was able to prepare soils to temperate soil temperature which serves as a potential alternative for growing temperate crops in the future, throughout the year under unpredictable climate changes.

Silicon Improves Chilling Tolerance During Early Growth of Maize by Effects on Micronutrient Homeostasis and Hormonal Balances.

Low soil temperature in spring is a major constraint for the cultivation of tropical and subtropical crops in temperate climates, associated with inhibition of root growth and activity, affecting early growth and frequently plant performance and final yield. This study was initiated to investigate the physiological base of cold-protective effects induced by supplementation with silicon (Si), widely recommended as a stress-protective mineral nutrient. Maize was used as a cold-sensitive model plant, exposed to chilling stress and low root-zone temperature (RZT) during early growth in a lab to field approach. In a pot experiment, 2–weeks exposure of maize seedlings to low RZT of 12–14°C, induced leaf chlorosis and necrosis, inhibition of shoot and root growth and micronutrient limitation (particularly Zn and Mn). These phenotypes were mitigated by seed treatments with the respective micronutrients, but surprisingly, also by Si application. Both, silicon and micronutrient treatments were associated with increased activity of superoxide dismutase in shoot and roots (as a key enzyme for detoxification of reactive oxygen species, depending on Zn and Mn as cofactors), increased tissue concentrations of phenolics, proline, and antioxidants, but reduced levels of H2O2. These findings suggest that mitigation of oxidative stress is a major effect of Zn, Mn, and Si applied as cold stress protectants. In a soil–free culture system without external nutrient supply, Si significantly reduced large leaching losses of Zn and Mn from germinating seeds exposed to low-temperature stress. Silicon also increased the translocation of micronutrient seed reserves to the growing seedling, especially the Zn shoot translocation. In later stages of seedling development (10 days after sowing), cold stress reduced the root and shoot contents of important hormonal growth regulators (indole acetic acid, gibberellic acid, zeatin). Silicon restored the hormonal balances to a level comparable with non-stressed plants and stimulated the production of hormones involved in stress adaptation (abscisic, salicylic, and jasmonic acids). Beneficial effects of Si seed treatments on seedling establishment and the nutritional status of Zn and Mn were also measured for a field-grown silage maize, exposed to chilling stress by early sowing. This translated into increased final biomass yield.

Contrasting surface soil hydrology regulated by biological and physical soil crusts for patchy grass in the high-altitude alpine steppe ecosystem

How the presence of biological soil crusts (BSCs) and physical soil crusts (PSCs) regulates surface soil hydrological processes in the high-altitude alpine ecosystems is still a pressing scientific issue owing to a lack of convincing field observation data. This study highlights the interesting phenomenon whereby BSCs and PSCs are jointly distributed in opposite orientations under a canopy of patchy Achnatherum splendens grass on the alpine steppe of the Qinghai Lake watershed (Qinghai-Tibet Plateau, northwestern China). The vegetation characteristics (plant species, cover, and biomass) and soil properties (volumetric soil water content, hydraulic conductivity, temperature, salinity, and macroporosity) were investigated for BSCs zones, PSCs zones, and interpatch zones (IPZs) in the A. splendens patches (ASPs) system. The experimental results show that BSCs increased infiltration during wet periods by increasing significantly greater hydraulic conductivity and macroporosity (p < 0.01), and reduced soil evaporation by maintaining a lower soil temperature than PSCs and IPZs during dry periods. BSCs had an important role in improving water retention in ASPs and thereby provided highly favorable conditions for plant recruitment and survival. However, PSCs reduced the infiltration capacity of surface soils and were suspected of generating runoff after intense rainfall events, which might promote connectivity of the horizontal water flux for ASPs. PSCs had a negative effect on the vegetation community by creating a saline environment (e.g. 28-fold higher salinity than for BSC zones and IPZs at 5 cm depth) for other herbaceous plants. The predominant wind direction, canopy effects of A. splendens on local microclimate, and salt accumulation were identified as the main factors determining the opposite distribution of BSCs and PSCs. The results suggest that BSCs and PSCs play contrasting roles in soil hydrology in ASPs, and provide valuable insights for understanding the spatial distribution of soil crusts and vascular plants as well as their interactions in high-altitude alpine steppe ecosystems.

Effect of tillage and crop residue on soil temperature following planting for a Black soil in Northeast China

Crop residue return is imperative to maintain soil health and productivity but some farmers resist adopting conservation tillage systems with residue return fearing reduced soil temperature following planting and crop yield. Soil temperatures were measured at 10 cm depth for one month following planting from 2004 to 2007 in a field experiment in Northeast China. Tillage treatments included mouldboard plough (MP), no till (NT), and ridge till (RT) with maize (Zea mays L.) and soybean (Glycine max Merr.) crops. Tillage had significant effects on soil temperature in 10 of 15 weekly periods. Weekly average NT soil temperature was 0–1.5 °C lower than MP, but the difference was significant (P < 0.05) only in 2007 when residue was not returned in MP the previous autumn. RT showed no clear advantage over NT in increasing soil temperature. Higher residue coverage caused lower soil temperature; the effect was greater for maize than soybean residue. Residue type had significant effect on soil temperature in 9 of 15 weekly periods with 0–1.9 °C lower soil temperature under maize than soybean residue. Both tillage and residue had small but inconsistent effect on soil temperature following planting in Northeast China representative of a cool to temperate zone.

Water relations in olive trees under cold conditions

Abstract A common effect of cold temperatures on plants is dehydration. When the temperature decreases below some specific thresholds, olive trees, as other sensitive crops, reduce their leaf water potential and transpiration rates even when soil water content is not limiting. The aim of our trial was to study the relationships between climatic conditions and plant water status, to elucidate the different roles played by soil and air temperature. Olive plants were randomly divided in heated and non-heated soils and plant water status was weekly determined. In heated plants, soil temperature was maintained above 15 °C, while in non-heated soils, plants were maintained in field conditions. The effect of air temperature was determined by analyzing the plant’s water status in heated plants, while the effect of soil temperature was studied through the plant water status differences between heated and non-heated soil treatments. Plant water status in the heated treatment fit into the vapour pressure deficit model, according to previous works conducted in warm conditions. Plant water status differences showed great variations in short periods of time, an unusual event with warm temperatures. In this study, two thresholds of soil temperature were found: above 10 °C, it had no effect on plant water status; between 10 °C and 6.5 °C, there was a linear relationship between plant water status and soil temperature, and below 6.5 °C, wind and relative humidity determined the plant water status. Our hypothesis is that low soil temperature produces a high resistance to water movement, while wind and relative humidity control the desiccation process in the leaf, so the great variations in plant water status are only at the leaf level and can therefore change quickly.

Soil degassing at the Los Humeros geothermal field (Mexico)

The Los Humeros geothermal field is the third most important producer of geothermal electricity (70MW) in Mexico. Geothermal fluids are hosted in fractured andesitic lavas and mostly consist of high enthalpy steam with limited water content (vapor fraction>0.9). Despite the high reservoir temperature (~300–400°C), thermal manifestations at the surface are scarce and locally appear as steaming grounds, weak steam vents and advanced argillic alteration. Geothermal fluid upflow from the reservoir towards the surface is limited by welded ignimbrite deposits that act as a low-permeability barrier. In this study, we present the first measurements of CO2, CH4 and H2S degassing rates from the soil performed at Los Humeros. Flux measurements were complemented with δ13C composition of degassing CO2 and soil temperatures to discuss gas origin and thermal anomalies. We measured high soil degassing rates (up to 7530gm−2d−1 CO2, 33gm−2d−1 CH4 and 22gm−2d−1 H2S) in three localized areas (Humeros North – HN, Humeros South – HS and Xalapazco – XA) as well as high soil temperatures reaching the boiling temperature at the local altitude (90.6°C). The particular location of these three areas suggests that the steam-dominated reservoir degases to the surface through permeable faults crossing the ignimbritic deposits. The remaining surveyed areas are characterized by weak CO2 fluxes (≤44gm−2d−1), non-detectable CH4 and H2S fluxes, and lower soil temperatures (5–21°C). The compositions in δ13CCO2 from HN-HS-XA areas (δ13CCO2=−7.94 to −2.73‰) reflect a magmatic source with some possible contribution from the sedimentary basement, as well as fractionation induced by boiling and CO2 dissolution in shallow water bodies. We also discuss the processes causing the spread in CO2/CH4 flux ratios. Finally, we estimate the heat output from the three high degassing areas to a value of 16.4MWt.

Soil Carbon Dioxide Respiration in Switchgrass Fields: Assessing Annual, Seasonal and Daily Flux Patterns

Quantifications of annual soil respiration in switchgrass systems are limited to the growing season or coarse-scale temporal sampling. This study evaluates daily and seasonal soil CO2 respiration in switchgrass croplands. Hourly measurements during a 12-month period were taken for soil CO2 flux, soil temperature, and soil moisture. Although both soil temperature and moisture were positively correlated with soil CO2 flux rates, soil temperature was the primary driver of soil respiration. During winter, lower soil temperatures corresponded with significant decreases in average daily CO2 flux rates, however, CO2 pulses associated with precipitation events increased flux rates up to three times the seasonal daily average. Soil temperature influenced both daily and seasonal flux patterns where the highest flux rates, up to 31.0 kg CO2 ha−1 h−1, were observed during the warmest hours of the day (13:00 to 15:00) and during the warmest season (Summer). Summer and Spring emissions combined accounted for 80.1% of annual flux, indicating that exclusion of non-growing season time periods may result in an underestimation of total annual CO2 efflux. Our results indicate that inclusion of the non-growing season and a fine-resolution temporal sampling approach provides more accurate quantifications of total annual CO2 emissions in switchgrass croplands.

Differential effects of feather and Sphagnum spp. mosses on black spruce germination and growth

Abstract The composition of the bryophyte layer influences boreal forest regeneration and growth through its effect on soil conditions. Canopy openings in boreal spruce stands can favor the expansion of Sphagnum spp. in the understory at the expense of feather mosses. We use an experimental approach in both paludified field and greenhouse fully-randomized conditions to examine the differential effects of these two ground cover types on black spruce germination and growth, specifically the role of nutrient limitation in generating these effects. We also tested the impact of ground cover shading, simulating the effect of a closed forest canopy on the ground layer, with the assumption that the stress induced to mosses, especially to Sphagnum spp., would have a beneficial impact on tree growth. The two moss types had no differential effects on spruce germination and 0–6-month-old seedling growth in the greenhouse. However, the growth of 2-year-old seedlings in the greenhouse was lower in Sphagnum spp. than in feather mosses. This negative effect was removed by fertilization, suggesting that soil nutrient availability could explain the seedling growth difference between moss types. Greenhouse 2-year-old seedlings also allocated a greater proportion of biomass to roots in Sphagnum spp. than in feather mosses. In the field, feather and Sphagnum spp. mosses had no differential effects on 3-year-old seedling growth, and ground cover shading did not have any short-term positive impact on spruce growth. Although they were not validated in the field, the results we obtained in the greenhouse suggest that the replacement of feather mosses by Sphagnum spp. mosses do not only affect spruce growth through the build-up of an organic layer often associated with low soil temperature and excess water, but also through more direct effects on nutrient availability. Therefore, silvicultural treatments that would favor Sphagnum spp. expansion at the expense of feather mosses, such as partial or total harvesting with protection of regeneration and soils, may result in subsequent tree growth problems even in sites with moderate organic layer accumulation.

Early-season Production of Grafted Seedless Cucumbers in High Tunnels

Seedless cucumber (Cucumis sativus) is a popular and high-value crop found in many local food markets. Worldwide, it is the third most important high tunnel crop after tomato (Solanum lycopersicum) and pepper (Capsicum annuum). One challenge of growing seedless cucumbers in high tunnels is low soil temperatures in the early season that suppress plant growth even when air temperatures would be adequate. Grafting cucumbers to enhance crop tolerance to suboptimal temperature stresses has been widely used in Asian countries. However, little information is available in the United States about graft compatibility, cold hardiness, and seasonal extension potential of growing grafted seedless cucumbers in high tunnels. In this study, we tested the effects of grafting with two winter squash (Cucurbita moschata) rootstocks (‘Titan’ and ‘Marvel’) on vegetative growth and yield of three seedless cucumbers (‘Excelsior’ pickling cucumber, ‘Socrates’ Beit Alpha cucumber, and ‘Taurus’ long-type cucumber) in the spring seasons of 2016 and 2017 in high tunnels located in U.S. Department of Agriculture (USDA) hardiness zone 6. Nongrafted plants were included as controls. All grafted plants survived the suboptimal temperature stress during transplant period, whereas 59% of nongrafted plants died in the 2016 season. Irrespective of rootstock and cucumber cultivar, vine growth rates of nongrafted cucumbers in April of both years were lower than those of the grafted crops. Cucumber cultivars Excelsior and Taurus grafted onto Marvel winter squash rootstock had higher yields in May 2016 compared with the yields of the nongrafted plants in the same month. The enhanced early-season yields of grafted plants were observed on cucumber cultivars Excelsior and Socrates in 2017 regardless of rootstocks. Grafting also increased the entire season’s yields of the three cucumber cultivars in 2017, but not in 2016. More comprehensive evaluations about cold tolerances of newly released cucumber rootstocks are needed. Further studies are also warranted to improve our understanding of effects of rootstock and scion interactions on cucumber growth and yield in high tunnel production.

Dominant plant species shape soil bacterial community in semiarid sandy land of northern China.

Plant species affect soil bacterial diversity and compositions. However, little is known about the role of dominant plant species in shaping the soil bacterial community during the restoration of sandy grasslands in Horqin Sandy Land, northern China. We established a mesocosm pots experiment to investigate short‐term responses of soil bacterial diversity and composition, and the related soil properties in degraded soils without vegetation (bare sand as the control, CK) to restoration with five plant species that dominate across restoration stages: Agriophyllum squarrosum (AS), Artemisia halodendron (AH), Setaria viridis (SV), Chenopodium acuminatum (CA), and Corispermum macrocarpum (CM). We used redundancy analysis (RDA) to analyze the association between soil bacterial composition and soil properties in different plant species. Our results indicated that soil bacterial diversity was significantly lower in vegetated soils independent of plant species than in the CK. Specifically, soil bacterial species richness and diversity were lower under the shrub AH and the herbaceous plants AS, SV, and CA, and soil bacterial abundance was lower under AH compared with the CK. A field investigation confirmed the same trends where soil bacteria diversity was lower under AS and AH than in bare sand. The high‐sequence annotation analysis showed that Proteobacteria, Actinobacteria, and Bacteroidetes were the most common phyla in sandy land irrespective of soil plant cover. The OTUs (operational taxonomic units) indicated that some bacterial species were specific to the host plants. Relative to bare sand (CK), soils with vegetative cover exhibited lower soil water content and temperature, and higher soil carbon and nitrogen contents. The RDA result indicated that, in addition to plant species, soil water and nitrogen contents were the most important factors shaping soil bacterial composition in semiarid sandy land. Our study from the pot and field investigations clearly demonstrated that planting dominant species in bare sand impacts bacterial diversity. In semiarid ecosystems, changes in the dominant plant species during vegetation restoration efforts can affect the soil bacterial diversity and composition through the direct effects of plants and the indirect effects of soil properties that are driven by plant species.

Importance of Soil Temperature for the Growth of Temperate Crops under a Tropical Climate and Functional Role of Soil Microbial Diversity.

A soil cooling system that prepares soil for temperate soil temperatures for the growth of temperate crops under a tropical climate is described herein. Temperate agriculture has been threatened by the negative impact of temperature increases caused by climate change. Soil temperature closely correlates with the growth of temperate crops, and affects plant processes and soil microbial diversity. The present study focuses on the effects of soil temperatures on lettuce growth and soil microbial diversity that maintains the growth of lettuce at low soil temperatures. A model temperate crop, loose leaf lettuce, was grown on eutrophic soil under soil cooling and a number of parameters, such as fresh weight, height, the number of leaves, and root length, were evaluated upon harvest. Under soil cooling, significant differences were observed in the average fresh weight (P<0.05) and positive development of the roots, shoots, and leaves of lettuce. Janthinobacterium (8.142%), Rhodoplanes (1.991%), Arthrospira (1.138%), Flavobacterium (0.857%), Sphingomonas (0.790%), Mycoplana (0.726%), and Pseudomonas (0.688%) were the dominant bacterial genera present in cooled soil. Key soil fungal communities, including Pseudaleuria (18.307%), Phoma (9.968%), Eocronartium (3.527%), Trichosporon (1.791%), and Pyrenochaeta (0.171%), were also recovered from cooled soil. The present results demonstrate that the growth of temperate crops is dependent on soil temperature, which subsequently affects the abundance and diversity of soil microbial communities that maintain the growth of temperate crops at low soil temperatures.

Prescribed Fire in Grassland Butterfly Habitat: Targeting Weather and Fuel Conditions to Reduce Soil Temperatures and Burn Severity

Prescribed burning is a primary tool for habitat restoration and management in fire-adapted grasslands. Concerns about detrimental effects of burning on butterfly populations, however, can inhibit implementation of treatments. Burning in cool and humid conditions is likely to result in lowered soil temperatures and to produce patches of low burn severity, both of which would enhance survival of butterfly larvae at or near the soil surface. In this study, we burned 20 experimental plots in South Puget Sound, Washington, USA, prairies across a range of weather and fuel conditions to address the potential for producing these outcomes. Risk to diapausing butterfly larvae, assessed by measuring subsurface soil temperatures and heat dosages, was lower when air temperature was less than 26°C and dead fuel moisture was greater than 9 %. The likelihood that unburned or low-severity patches would be left was affected by dead fuel moisture, but also required pre-existing fuel discontinuities. Burns conducted in the morning hours during the summer drought season (the main prescribed-fire season in this system) were cooler and had lower severities. This research increases our understanding of how fine fuel moisture and fuel continuity during grassland burning can affect fire intensity, severity, and spread. It also provides support for burning earlier in the day as a way to increase burn heterogeneity and has allowed us to create recommendations for burning in sensitive butterfly habitat.

Effect of snow cover on soil frost penetration

AbstractSnow cover occurrence affects wintering and lives of organisms because it has a significant effect on soil frost penetration. An analysis of the dependence of soil frost penetration and snow depth between November and March was performed using data from 12 automated climatological stations located in Southern Moravia, with a minimum period of measurement of 5 years since 2001, which belong to the Czech Hydrometeorological institute. The soil temperatures at 5 cm depth fluctuate much less in the presence of snow cover. In contrast, the effect of snow cover on the air temperature at 2 m height is only very small. During clear sky conditions and no snow cover, soil can warm up substantially and the soil temperature range can be even higher than the range of air temperature at 2 m height. The actual height of snow is also important – increased snow depth means lower soil temperature range. However, even just 1 cm snow depth substantially lowers the soil temperature range and it can therefore be clearly seen that snow acts as an insulator and has a major effect on soil frost penetration and soil temperature range.

Yield loss compensation effect and water use efficiency of winter wheat under double-blank row mulching and limited irrigation in northern China

Maize straw residues as a surface mulching material would be an effective soil water-saving practice in wheat production for a wheat-maize rotation system in northern China. Additionally, combining a mulching pattern and limited irrigation could play an important role in enhancing the productivity of winter wheat. Therefore, open field experiments were carried out during 2012–2014 to study soil water content in depth, water use efficiency (WUE), soil temperature, wheat grain yield and root parameters under a mulching pattern [each-row mulching (ERM) and double-blank row mulching (DRM) with three mulching masses of 0. 4.5 and 9.0tha−1] and limited irrigation [no irrigation (I0) and one-time irrigation in winter (I1)].Results indicated that wheat yields increased (mean 3.3%) or decreased (mean 5.4%) a little under ERM groups with no irrigation. Irrigation for each row of mulch increased the wheat yield (mean 8.8%). With or without irrigation, yields under DRM0 were lower compared to ERM0, whereas, DRM4.5 and DRM9.0 had a higher grain yield than ERM4.5 and ERM9.0 (mean 25% under I0 and 18.8% under I1) as well as DRM0 (mean 24.1%). The DRM patterns with a high yield could have an equal effect with irrigation in winter. Additionally, irrigation could enhance the effects of DRM on wheat yield increase (mean 6.87tha−1in DRM4.5 and 7.06tha−1 in DRM9.0). Effective tillers and above-ground biomass would be the key factors for determining wheat yield, especially under certain mulching patterns, although these effects were not reflected in wheat roots.Mulching on soil temperature had a more significant difference in an early growth period than the later stages of wheat. An additional feature was that the DRM pattern had a persistent heat preservation effect in the regrowth stage, while there was a lower soil temperature in ERM groups in this stage when there was no irrigation. Mulching managed to shorten the period of negative accumulated temperatures of wheat (mean of 7days under ERM and 15days under DRM) under I0. Winter water irrigation enhanced the shorten effect to a certain extent. Mulching had a more significant water conservation effect in the overwinter stage with lower precipitation and higher soil evaporation. Soil water content under DRM groups was richer than ERM groups in the late growth stage, when there was lower plant density and evapotranspiration, but there was a higher yield and WUE (with a mean of 18.6% under I0 and 20.3% under I1).The results suggest that the DRM pattern optimizes soil temperature, water content, balance roots and group effects as well as increasing wheat yield. Thus, this approach could be a better field management option for wheat growth and yield production under the limitations of water in northern China.

Mulching type-induced soil moisture and temperature regimes and water use efficiency of soybean under rain-fed condition in central Japan

Soybean (Glycine max) is a high water-demand crop and grown under moderate temperature in Japan. To protect the crop from hot summer and to utilize rainfall for its cultivation, selection of appropriate mulching material(s) is crucial. For optimum production of the crop, soil moisture and temperature regimes as well as water use efficiency (WUE) of the crop were investigated under straw, grass, paper, plastic and bare soil (control) mulching under rain-fed condition at Gifu university farm in Japan. The mulching treatments, compared to the control, lowered soil temperature by 2°C at 5cm depth and 0.5°C at 15 and 25cm depths. The plastic and straw mulching stored the highest quantity of soil moisture at 5 and 15cm depths; the bare soil stored the lowest quantity. At 25cm depth, soil-moisture content was the highest under paper mulch but invariable under the other mulches. Plastic mulching reduced evaporation rate from the soil surface and, consequently, the reduced soil-water consumption (SWC) from the root zone augmented WUE of soybean. The paper mulching, by conserving soil-moisture and reducing soil temperature, provided better crop growth attributes, while the plastic mulching improved WUE of green soybean. Therefore, the plastic mulch performed best in reducing soil-water consumption and increasing WUE, while the paper mulch was good for soil-moisture conservation and temperature modification that increased soybean yield.

Seasonal dynamics of the ectomycorrhizal fungus Lactarius vinosus are altered by changes in soil moisture and temperature

Ectomycorrhizal fungi are important components of the carbon and nitrogen cycles in forest soils and improve the nutrient uptake of many plants. There have been few assessments of how soil fungal biomass is affected by climate; however, a good understanding of how soil mycelium is correlated with climate is essential to predict long-term responses to global warming. Soil extramatrical mycelia (EMM) of Lactarius vinosus, a highly valued and edible ectomycorrhizal species, was quantified by performing qPCR analyses of soil samples that were collected monthly from 28 long-term experimental plots. The belowground moisture and temperature of these plots were individually recorded every 2 h. L. vinosus soil EMM biomass fluctuated between 44 and 261 kg ha−1, with the maximum biomass occurring during spring months and the minimum occurring during winter and summer months. Mean mycelial turnover was estimated to occur 7.0 times year−1. Soil EMM was reduced under low soil temperatures and when there was a combination of high soil temperatures and low soil moisture, most likely caused by reduced C allocation from the host under both winter and summer conditions. Preliminary models using simulated reductions in soil moisture and increases in soil temperature showed that soil EMM increased significantly during winter–spring months, whereas EMM decreased significantly during summer months. These results suggest that warmer conditions would lengthen the period of L. vinosus biological activity during winter months, whereas increasing periods of drought would prevent the growth of this species during summer months. Our study shows significant soil EMM seasonality and highlights potential climate-driven annual cycle shifts of soil mycelia.

Growth performance and lignin content of Acacia mangium Willd. and Acacia auriculiformis A. Cunn. ex Benth. under normal and stressed conditions

Acacia mangium Willdenow and Acacia auriculiformis A. Cunningham ex Bentham are fast-growing species with wide environmental adaptability. Fast-growing species which thrive in otherwise non-arable problematic soil and which hold the added advantage of improving the condition of the soil, can be used to increase production area, and, thus, are highly desired. We investigated the growth performance and lignin content under normal and stressed conditions for these Acacia mangium Willd. and Acacia auriculiformis A. Cunn. ex Benth. Normal growing conditions was represented by fertile soil, high water-holding capacity due to low soil drainage, high organic matter, low soil temperature, overall consistent rainfall and relatively milder temperatures, whilst stressed conditions were achieved with a sandy soil with low fertility, low water-holding capacity due to high drainage and low organic matter, and high soil temperature accompanied by inconsistent monthly temperature and rainfall. Growth performance under normal conditions was significantly better compared to the stressed conditions. A. mangium performed better than A. auriculiformis under the normal conditions. However A. auriculiformis performed better under stressed conditions due to better adaptability. The lignin content under normal conditions fluctuated from one DBH class to another. As for the stress conditions, A. mangium exhibited incremental increases in lignin content with increasing biomass. In contrast, lignin content in A. auriculiformis decreased with increasing biomass. The differences in performance may be attributable to both the micro- and macro-environments and adaptive differences between the two species. For growth under normal conditions, A. mangium appears to be the superior choice, whereas for problematic soils, A. auriculiformis can be recommended. However, for the selection of superior plants with a combination of desired growth rates and lower lignin content the breeding of interspecific hybrids would be a desirable approach.