Field Water-holding Capacity Research Articles

Growth Performance and Osmolyte Regulation of Drought-Stressed Walnut Plants Are Improved by Mycorrhiza

This study aims to evaluate whether a selected arbuscular mycorrhizal fungus, Diversispora spurca, improves growth in drought-stressed walnut (Juglans regia L. cv. Qingxiang) plants and whether this improvement is associated with changes in osmolyte (fructose, glucose, sucrose, soluble protein, proline, and betaine) levels. After 60 days of soil drought treatment (50% of maximum field water-holding capacity), root D. spurca colonization rate and soil mycelium length decreased by 13.57% and 64.03%, respectively. Soil drought also inhibited the growth performance of aboveground (stem diameter, leaf number, leaf biomass, and stem biomass) and underground (root projected area, surface area, and average diameter) parts, with uninoculated plants showing a stronger inhibition than D. spurca-inoculated plants. D. spurca significantly increased these growth variables, along with aboveground part variables and root areas being more prominent under drought stress versus non-stress conditions. Although drought treatment suppressed the chlorophyll index and nitrogen balance index in leaves, mycorrhizal inoculation significantly increased these indices. Walnut plants were able to actively increase leaf fructose, glucose, sucrose, betaine, and proline levels under such drought stress. Inoculation of D. spurca also significantly increased leaf fructose, glucose, sucrose, betaine, proline, and soluble protein levels under drought stress and non-stress, with the increasing trend in betaine and soluble protein being higher under drought stress versus non-stress. Drought stress dramatically raised leaf hydrogen peroxide (H2O2) levels in both inoculated and uninoculated plants, while mycorrhizal plants presented significantly lower H2O2 levels, with the decreasing trend higher under drought stress versus non-stress. In conclusion, D. spurca symbiosis can increase the growth of drought-stressed walnut plants, associated with increased osmolyte levels and decreased H2O2 levels.

Assessing the effects of agricultural waste returning on soil moisture characteristics

AbstractAgricultural waste is an emerging and promising resource due to its abundant organic compounds and high water‐holding capacity. It plays a crucial role in improving soil water use efficiency and contributing to sustainable agricultural development. This study aimed to investigate the impact of returning agricultural waste on soil moisture characteristics. Different volume ratios (4:5:1:0, 3:5:1:1, 2:5:1:2, 1:5:1:3, and 0:5:1:4) of agricultural waste blend (AWB) consisting of cattle manure, yellow loam soil, wheat straw, and distiller's grains were examined, and the water‐holding performance of the five AWB ratios under various suction forces was compared. The analysis confirmed the suitability of the Van Genuchten‐Mualem model for fitting soil moisture characteristic curves at different ratios. The study also examined the influences of AWB ratios on soil‐specific water capacity, hydraulic parameters, and equivalent pore size. The results showed that agricultural waste effectively increased soil‐specific water capacity, available water content, soil WHC(Water‐holding capacity), and soil pore count. Furthermore, reducing cattle manure and increasing distiller's grains enhanced these effects. For instance, when the AWB ratio was 0:5:1:4, soil‐specific water capacity increased by 47.7%, while field WHC and available water content increased by 9.9% and 3.8%, respectively. Additionally, the number of extremely small and small pores increased by 1.4% and 0.77%, respectively. These findings provide valuable theoretical guidance for agricultural waste treatment and improving soil WHC. Based on the results, it is recommended to increase the proportion of distiller's grains and reduce organic fertilizer when using agricultural waste for improving soil WHC.

Poplar Sawdust Biochar Altered Community Composition of Dominant Soil Fungi but Not Bacteria Depending on Pyrolysis Temperature

There is a growing focus on the production of biochar from organic wastes and its forestry use. However, it is unclear how applying biochar pyrolyzed at different temperatures influences both soil bacterial and fungal communities. In this study, two kinds of biochar were pyrolyzed at 350 °C and 600 °C, from poplar sawdust, and then applied as an auxiliary substrate material (15% addition by volume) for the container seedling cultivation of Cyclocarya paliurus, a native timber and medically used tree species, to compare the response of the soil’s microbial traits. The results showed that after 5 months of cultivation, the addition of the biochar application improved the soil’s physical and chemical properties to a certain extent by decreasing its bulk density and increasing its field water-holding capacity, pH and organic carbon content. The soil’s pH and content of organic C, available N and available P were significantly higher in the substrate with the addition of the biochar pyrolyzed at 600 °C (Bioc600) than in that of the substrate with added pyrolyzed biochar at 350 °C (Bioc350). The biochar application also enhanced the soil’s microbial N (MBN) but showed no changes in the MBC/MBN ratio. The biochar application had no effect on the diversity and composition of the soil’s bacterial community, but showed a certain effect on its fungal community composition and had different influences between low and high pyrolysis temperatures. The relative abundance of several of the dominant fungal phyla and genera increased with the addition of biochar due to the increase in the soil’s pH when compared to the CK (no biochar or sawdust addition). When compared with Bioc350, the dominant phylum Basidiomycota and genus Vanrija further increased in abundance with Bioc600. These findings reveal the consistent effects of biochar pyrolysis temperature and demonstrate the different regulatory roles of biochar application in soil bacterial and fungal communities, providing valuable information on how biochar can effectively be used as a substrate for seedling cultivation.

Structural characteristics of the moss (bryophyte) layer and its underlying soil structure and water retention characteristics

The influence of the moss layer on soil structure and soil water retention is not well understood. Therefore, this study aims to investigate the changes in soil structure and soil water retention under moss layer and to reveal the influencing factors of these changes. 3D networks of moss layer and soil macropores were quantified using CT scanning and image analysis techniques, and soil water retention characteristics were explored through soil water retention curves (SWRCs) and VG model. The length densities of the soil macropores under the thin moss and thick moss layers were approximately 2.7 and 1.6 times higher than that under no moss cover. The soil water retention under the thin and thick moss layers were greater than those under no moss cover, with the highest plant-available water capacity under the thin moss layer. The maximum water-holding capacity of the moss layer was significantly positively correlated with the field water-holding capacity of the soil and negatively correlated with the equivalent diameter of the macropores, while the storage capacity of the moss layer was significantly and negatively correlated with the maximum effective water content of the soil. The field capacity (FC) and permanent wilting point (PWP) were significantly and positively correlated with the soil organic matter. The effect of the moss layer on water retention may be mainly realized by influencing the pore distribution and organic matter accumulation. The moss layer had a positive ecohydrological effect on soil water retention and even water conservation in forest soils.

Big-sized trees and higher species diversity improve water holding capacities of forests in northeast China

High water-holding forests are essential for adapting to drought climates under global warming, and a central issue is which type of forests could conserve more water in the ecosystem. This paper explores how forest structure, plant diversity, and soil physics impact forest water-holding capacities. We investigated 720 sampling plots by measuring water-holding capacities from 1440 soil and litter samples, 8400 leaves, and 1680 branches and surveying 18,054 trees in total (28 species). Water-holding capacities were measured as four soil indices (Maxwc, maximum water-holding capacity; Fcwc, field water-holding capacity; Cpwc, soil capillary water-holding capacity; Ncpwc, non-capillary water-holding capacity), two litter metrics (Maxwcl, maximum water-holding capacity of litters; Ewcl, effective water-holding capacity of litters), and canopy interception (C, the sum of estimated water interception of all branches and leaves of all tree species in the plot). We found that water-holding capacity in the big-sized tree plots was 4–25 % higher in the litters, 54–64 % in the canopy, and 6–37 % in the soils than in the small-sized plots. The higher species richness increased all soil water-holding capacities compared to the lowest richness plot. Higher Simpson and Shannon-Wiener plots had 10–27 % higher Ewcl and C than the lowest plots. Bulk density had the strongest negative relations with Maxwc, Cpwc, and Fcwc, whereas field soil water content positively affected them. Soil physics, forest structure, and plant diversity explained 90.5 %, 5.9 %, and 0.2 % of the water-holding variation, respectively. Tree sizes increased C, Ncpwc, Ewcl directly (p < 0.05), and richness increased Ewcl directly (p < 0.05). However, the direct effects from the uniform angle index (tree distribution evenness) were balanced by their indirect effect from soil physics. Our findings highlighted that the mixed forests with big-sized trees and rich species could effectively improve the water-holding capacities of the ecosystem.

Synergistic effects of biochar and carboxymethyl cellulose sodium (CMC) applications on improving water retention and aggregate stability in desert soils

Making improvements to the water-holding characteristics and water-erosion resistance of desert soils, particularly in inland extremely arid areas, is vital for achieving both sustainable water resource utilisation and food security. The aim of this study is to evaluate the effects of the co-application of biochar and carboxymethyl cellulose sodium (CMC) on the physical properties of sandy desert soil, including infiltration rate, saturated water conductivity, field water-holding capacity and aggregate stability. Sandy desert soil samples were collected from jujube plantations on the southern edge of the Taklimakan Desert in the Hotan Prefecture, Xinjiang, China. Five CMC application ratios (C0:0, C1:0.01 g/kg, C2:0.02 g/kg, C3:0.04 g/kg and C4:0.08 g/kg) and five biochar application ratios (B0:0, B1:1.0 g/kg, B2:2.0 g/kg, B3:4.0 g/kg and B4:8.0 g/kg) were designed and a total of 11 experimental treatments were performed, which were labelled as CK (control group), B2C0, B2C1, B2C2, B2C3, B2C4, B4C4, B0C2, B1C2, B3C2 and B4C2. Compared with CK, the combined application of biochar and CMC reduced the soil bulk density (BD) by 1.29–9.41% and the saturated hydraulic conductivity (Ks) by 29.64–94.98%, and increased the soil saturated water content (SSWC) by 8.81–30.74% and the water holding capacity (WHC) by 13.91–36.87%. Similarly, the water-stable aggregates that were co-applied with biochar and CMC increased by 29.10–256.86%. This resulted in significant improvement in the stability of sandy desert soil against water erosion. The principal component analysis (PCA) results found B4C4 to have the best comprehensive improvement effect. Therefore, 0.08 g/kg of CMC and 8.0 g/kg of biochar were used as recommended for improving the hydraulic properties of desert soils. Generally, CMC and biochar have a mutually complementary effect on improving sandy desert soil, providing new ideas and approaches for the improvement of soil and the sustainable development of agriculture in desert areas.

Conceptual principles of watering control under irrigation

The conceptual principles of watering control under irrigation using decision support systems are outlined. Based on the analysis and research of foreign and domestic authors, it has been proven that the effectiveness of watering control depends to a large extent on the methodological approaches used to determine the terms and rates of watering in various decision support systems. It is shown that the most complete potential of varieties and hybrids of various types of crops under irrigation can be realized when establishing and implementing irrigation regimes ensuring the moisture supply of the soil root layer in a narrow range of high humidity (close to field water-holding capacity (FWHC) during the entire growing season.&#x0D; It was grounded that the implementation of such irrigation regimes is possible only by applying decision support systems using GIS technologies, which combine hydrogeological models for calculation and forecasting of watering terms and rates, based on the use of soil moisture potential as a criterion of moisture supply availability for plants and Earth remote sensing data (ERSD). Such a combination makes it possible to analyze and apply measurement and forecasting data to the areas not covered by ground observations and provides highly efficient ecologically safe irrigation providing high irrigation water productivity and ecological safety of irrigation.&#x0D; The implementation of these principles in the practice of irrigation management ensures the yield of irrigated crops as of 0.85-0.90 of the potential of modern varieties and hybrids, while simultaneously reducing the consumption of irrigation water per unit of yield, as well as minimizing or eliminating losses of irrigation water due to infiltration, development of flooding processes, salinization, and secondary salinization of soils.

Synergism Between Water Management and Phosphorus Supply Enhances the Nodulation and Root Growth and Development of Chinese Milk Vetch (Astragalus sinicus L.).

The response of root development and nodule formation of the manure crop Chinese milk vetch to different levels of soil moisture and phosphorous (P) fertilizer remains unclear. In this study, a pot experiment was performed to trace the root growth and nodule formation of Chinese milk vetch at the seedling, branching and full-flowering stages, under various soil moisture gradients [25% (W1), 50% (W2), 75% (W3), and 100% (W4) of the maximum field water-holding capacity] and P levels [0 (P0), 30 (P1), 60 (P2), and 90 (P3) kg hm–2]. The root/shoot ratio, root vitality, number of nodules, nodule weight, and nitrogenase activity were affected remarkably by soil moisture or the level of added P across the whole stage. Differences were found in the interaction effect between soil moisture and added P on the characteristic indices of the root and nodule at the different growth stages. There were obvious differences in root activity and nitrogenase activity at seedling stage, but no evident differences were found in other indices. Certain differences were also found in the indicators mentioned above at the branching stage. W1P0 and W2P0 showed the highest root/shoot ratio, W2P2 and W3P2 resulted in the highest root activity; W3P3 and W3P2 had the highest number and weight of nodules; and W3P2, W2P2, and W3P1 had higher nitrogenase activity than the other treatments at the full-flowering stage. The application of P at 60 kg hm–2 and the relative soil moisture of 75% was the best P-water combination suitable for the root development, nodule formation, and nitrogen fixation of Chinese milk vetch. This study will provide a theoretical basis for the production of this plant by managing the synergistic interaction between P fertilizer and soil moisture.

Effects of water saving and nitrogen reduction on the yield, quality, water and nitrogen use efficiency of Isatis indigotica in Hexi Oasis

Isatis indigotica planting is the backbone of the medicinal industry in Hexi Oasis, Gansu. In order to solve the problems insufficient water resources and excessive application of nitrogen fertilizer in this area, this paper explored the irrigation and nitrogen levels that can meet the multiple goals of Isatis indigotica. The two-factor split-plot field experiment (2018‒2019) was conducted in Minle County, Gansu Province, China, which contains 9 treatments. There were three levels of irrigation water: W1(low), W2(medium), and W3(high). The soil moisture contents were 60–70%, 70–80%, and 80–90% of the field water-holding capacity, respectively. The nitrogen application rate was classified into three levels, N1(low), N2(medium) and N3(high), which were 150, 200 and 250 kg N/ha, respectively. The standard local irrigation water amount and nitrogen application rate corresponded to W3N3. The results showed that the yield of Isatis indigotica increased first and then decreased with the increase of irrigation amount and nitrogen application rate, the yield of W2N2 is 12.2–17.1% higher than that of W1N1, the yield of W3N3 was 12.1–17.5% lower than that of W2N2. Saving water and reducing nitrogen can improve the quality of Isatis indigotica, compared with W3N3, the indigo, indirubin, (R,S)-epigoitrin and polysaccharides of W2N2 increased by 4.5–5.9%, 2.7–3.1%, 5.2–6.0%, and 1.8–2.1%, respectively. With the increase of nitrogen application rate, the water use efficiency (WUE) first increased and then decreased, as the irrigation volume increases, WUE decreases. Compared with W3N3, the WUE of W2N2 increased by 24.3–27.2%. With the increase of water input, the nitrogen fertilizer use efficiency (NUE) first increased and then decreased, as the nitrogen application rate increases, NUE decreases. Compared with W3N3, the NUE of W2W2 increased by 31.8–34.5%. Therefore, W2N2 can improve quality and increase water and nitrogen utilization efficiency on the basis of ensuring yield.

Bottom-up redistribution of biomass optimizes energy allocation, water use and yield formation in dryland wheat improvement.

Modern wheat cultivars have been developed having distinct advantages in many aspects under drought stress, such as plasticity in biomass allocation and root system architecture. A better understanding of the biomass allocation mechanisms that enable modern wheat to achieve higher yields and yield-based water use efficiency (WUEg ) is essential for implementing best management strategies and identifying phenotypic traits for cultivar improvement. We systematically investigated the biomass allocation, morphological and physiological characteristics of three ploidy wheat genotypes under 80% and 50% field water-holding capacity (FC) conditions. Some crucial traits were also assessed in a complementary field experiment. The diploid and tetraploid genotypes were found to allocate more biomass to the root system, especially roots in the topsoil under drought stress. Our data illustrated that lower WUEg and yield of these old genotypes were due to excessive investment in the root system, which was associated with severely restricted canopy development. Modern hexaploid genotypes were found to allocate smaller biomass to roots and larger biomass to shoots. This not only ensured the necessary water uptake, but also allowed the plant to distribute more assimilates and limited water to the shoots. Therefore, the hexaploid genotypes have evolved a stable plant canopy structure to optimize WUEg and grain yield. This study demonstrated that the biomass shift from below ground to above ground or a more balanced root:shoot ratio tended to optimize water use and yield of the modern cultivars. This discovery provides potential guidance for future dryland wheat breeding and sustainable management strategies. © 2021 Her Majesty the Queen in Right of Canada Journal of The Science of Food and Agriculture © 2021 Society of Chemical Industry. Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada.

Effects of Crop and Grass Intercropping on the Soil Environment in the Karst Area

The karst area in Southwest China is facing the challenges of environmental degradation and agricultural safety. Intercropping is a green and efficient planting mode that can make full use of the differences in crops’ physiological and ecological characteristics and land and climate resources while considering the environmental and yield benefits. This study selected five treatments: Salvia miltiorrhiza monoculture, Dactylis glomerata intercropped with S. miltiorrhiza, Cichorium intybus intercropped with S.miltiorrhiza, Trifolium repens intercropped with S.miltiorrhiza, and Lolium perenne intercropped with S.miltiorrhiza. Using one-way ANOVA, principle component analysis (PCA), and linear correlation analysis, we analyzed the changes in the soil physicochemical factors and the coupling relationship between them in the intercropping mode. The results showed that at different soil depths, the soil bulk density in the intercropping mode was significantly lower than that in the single cropping mode (p &lt; 0.05), and the soil water content and total porosity were significantly increased (p &lt; 0.05). There were no significant differences in soil pH among the five models (p &gt; 0.05), the content of soil organic matter was significantly higher than that in the single cropping mode (p &lt; 0.05), and the content of nitrogen and phosphorus also showed different changes. The correlation analysis showed that there was no significant correlation between the pH and soil physical properties (p &gt; 0.05); bulk density and chemical properties were negatively correlated, while the soil water content, field water-holding capacity, and total porosity were significantly positively correlated with the chemical properties (p &gt; 0.05). Therefore, it is suggested to strengthen the management of agricultural grass intercropping, improve soil pore structure, regulate the distribution of soil water and fertilizer, and improve the resilience of agricultural systems in the karst area of southwest China.

Effect of bentonite as a soil amendment on field water-holding capacity, and millet photosynthesis and grain quality

A field experiment was conducted in a semi-arid region in northern China to evaluate the effects of bentonite soil amendment on field water-holding capacity, plant available water, and crop photosynthesis and grain quality parameters for millet [Setaria italic (L.) Beauv.] production over a 5-year period. Treatments included six rates of bentonite amendments (0, 6, 12, 18, 24 and 30 Mg ha−1) applied only once in 2011. The application of bentonite significantly (P < 0.05) increased field water-holding capacity and plant available water in the 0–40 cm layer. Bentonite also significantly (P < 0.05) increased the emergence rate, above-ground dry matter accumulation (AGDM), net photosynthesis rate (Pr), transpiration rate (Tr), soil and plant analysis development (SPAD) and leaf water use efficiency (WUE). It also increased grain quality parameters including grain protein, fat and fiber content. Averaged over all the years, the optimum rate of bentonite was 24 Mg ha−1 for all plant growth and photosynthesis parameters except for grain quality where 18 Mg ha−1 bentonite had the greatest effect. This study suggests that bentonite application in semi-arid regions would have beneficial effects on crop growth and soil water-holding properties.

Investigation of biochars application on potassium forms and dynamics in a calcareous soil under different moisture conditions

ABSTRACT Biochar due to its high K content may affect K forms and dynamics. The effect of biochars produced from licorice root pulp, municipal waste and cow manure at 300 °C and 600 °C on K forms, release and fixation in a loamy calcareous soil was investigated. The soil samples were analyzed after biochar application and incubation at field water-holding capacity or saturation conditions. The cow manure and municipal waste biochars increased all K forms, while licorice root pulp biochar only increased exchangeable K (10%). Cumulative K released to 0.01 M CaCl2 for the control soil was 101 mg kg−1, increasing to 108, 182 and 418 mg kg−1, with the application of licorice root pulp, municipal waste and cow manure biochars produced at 300 °C, and increased to 112, 200 and 486 mg kg−1 with the application of the biochars produced at 600 °C, respectively. Generally, 0.025 M CaCl2 extracted more K than 0.01 M CaCl2 (means of 250 vs. 230 mg kg−1). Saturation had a smaller effect on K forms and dynamics; increasing non-exchangeable K. Biochar increased soil K fixation. Biochar depending on its origin and pyrolysis conditions may be used as an amendment for increasing K supplying power of calcareous soils.

Effects of high CO2 concentration, drought, and their interaction on different stay-green wheat seedlings

In this study, a pot experiment was carried out to examine the effects of high CO2 concentration, drought and interaction on seedling growth traits, biomass accumulation and physiological characteristics of different stay-green wheat seedlings, with a stay-green wheat variety Yannong 19 and a non stay-green wheat variety Hanxuan 3 as test materials. There were four treatments in the Open Top Chamber with factorial of CO2 concentration (370 μmol·mol-1 vs 550 μmol·mol-1) and drought (45%-55% vs. 75%-85% of field water-holding capacity). Drought significantly inhibited the growth and development of wheat seedlings, while CO2 concentration significantly increased the number of tillers and promoted the growth and development of wheat seedlings. Under drought condition, high CO2 concentration increased the number of tillers of Hanxuan 3 and Yannong 19 by 61.0% and 42.3%, respectively. Under both water conditions, high CO2 concentration significantly increased the biomass of wheat seedlings, and decreased the content of peroxidase and proline in leaves. Under drought condition, high CO2 concentration showed stronger "fertilizer effect". Furthermore, different varieties had different responses to high CO2 concentration, with higher sensitivity of Hanxuan 3 to enhancement of CO2 concentration. Under the scenario of increasing CO2 concentration, the amount of irrigation water applied to a field can be appropriately reduced for efficient use of water resources. Meanwhile, it is necessary to pay attention to the selection of suitable wheat varieties.

Effects of soil water stress and atmospheric CO2 concentration on photosynthetic and post-photosynthetic fractionation

Analysis of plant photosynthesis and post-photosynthetic fractionation can improve our understanding of plant physiology and water management. By measuring δ13C in the atmosphere, and δ13C of soluble compounds in leaves and branch phloem of Platycladus orientalis, we examined discrimination pattern, including atmosphere-leaf discrimination during photosynthesis (ΔCa-leaf) and leaf-twig discrimination during post-photosynthesis (ΔCleaf-phlo), in response to changes of soil water content (SWC) and atmospheric CO2 concentration (Ca). The results showed that ΔCa-leaf reached a maximum of 13.06‰ at 95%-100% field water-holding capacity (FC) and Ca 400 μmol·mol-1, and a minimum of 8.63‰ at 35%-45% FC and Ca 800 μmol·mol-1. Both stomatal conductance and mesophyll cell conductance showed a significant linear positive correlation with ΔCa-leaf, with a correlation coefficient of 0.43 and 0.44, respectively. ΔCleaf-phlo was not affected by SWC and Ca. Our results provide mechanism of carbon isotopes fractionation and a theoretical basis for plant survival strategies in response to future climate change.

Evaluation of the composition, properties and fertility of Haplic Ferralsol on the fields abandoned for five years in the Republic of Chad

The article deals with the fertility of red ferralitic soils in the Republic of Chad. The studies were carried out in the period between 2016 and 2018 in the southern part of the province of Moundou on the red ferralitic soils (Haplic Ferralsol)of the Cotton-Chad farm, which cultivates cotton first of its formation. Haplic Ferralsols are characterized by significant reservoir thickness and are not rich in nutrients. The aim of our research was to study the composition and properties of the Haplic Ferralsols of the fields abandoned for five years for their use under cotton export culture. We have evaluated the morphological structure of the soil on neglected fields and its description by genetic horizons, studied the particle size distribution of the soil profile, its gross composition, cation exchange capacity, the content of exchangeable cations, and also considered the agrochemical and agrophysical properties of soil horizons. It has been established that Haplic Ferralsols have their own characteristics: red color, thick soil profile and a gradual transition between genetic horizons, and lightweight granulometric composition in the upper part of the profile. The basis of the gross chemical composition of Haplic Ferralsols is SiO 2 , Fe 2 O 3 and Al 2 O 3 , the content of which varies depending on the depth of the soil profile within the ranges of 61.83–82.73 %, 3.50–6.40 % and 11.46–29.25 % correspondingly. Haplic Ferralsols are characterized by a high cation exchange capacity (6.6–11.1 сmol (eq)/kg). Among the exchangeable cations, calcium (Ca 2+ ) is the most essential. Haplic Ferralsols are moderately provided with humus. In the upper soil layers (up to 42 cm), its content varied within 1.53–1.66 %. Soils are characterized by acidic reactions – from moderately acidic in the upper horizons to very strongly acidic in the lower horizon. The content of mobile compounds of phosphorus and potassium in the profile is low and very low, respectively, 0.76–1.09 mg/100 g and 0.05–1.48 mg/100 g. According to its agrophysical properties, the soil may be used for cotton growing. In the upper soil layer (0–42 cm) the bulk density is 1.36–1.45 g/cm 3 , the total porosity is 45.9–48.9 % and the field water-holding capacity is 22.4–25.7 %.

Response of water-soluble salt accumulation in weathered gneiss spoil substrate to the addition of superabsorbent polymer under a semiarid climate

Superabsorbent polymer (SAP) has been widely used to improve soil moisture conditions in the ecological restoration of mining land. The effect of SAP on water-soluble salt movement in SAP-modified gneiss spoil in a semiarid region was studied in this experiment. Weathered gneiss spoil, dress soil, SAP, and turf were mixed via the L25(56) orthogonal test, and the semiarid environmental conditions were controlled for 1 year in a climate chamber. The results showed that bulk density, field water-holding capacity, and daily average evaporation rate of the substrate were dominated by the proportions of the soil and turf contents but were not significantly influenced by the SAP. The water-soluble salt in the top layer of the substrate increased significantly as the SAP concentration increased; i.e., it increased by 36.5% per 0.1% increase in the SAP within the range of 0 to 1%. The major ions influenced by the SAP were Na+, Mg2+, Ca2+, Cl−, and SO42−. The SAP decreased the pH of the substrate before the experiment, but only the top layer was influenced by the increase in the SAP after 1 year. The electrical conductivity (EC), which reflects the content of soluble ions in different substrate layers, was significantly influenced by the SAP in the following order: EC-middle layer < EC-bottom layer < EC-top layer. Based on the above results, we can conclude that the strong water and salt ion absorption ability of the SAP may limit the leaching of water-soluble ions and aggravate the accumulation of surface salts under semiarid environmental conditions. This study will be helpful for understanding the salt accumulation caused by the use of SAP in the remediation of mine spoil with high soluble salt contents.

Урожайність насіння томата сорту легінь залежно від схеми посіву та удобрення в Південному Степу України

Урожайність насіння томата сорту легінь залежно від схеми посіву та удобрення в Південному Степу України

Low-volume irrigation systems influence Pratylenchus penetrans populations, root colonization by arbuscular mycorrhizal fungi, and replant establishment of sweet cherry

Abstract A four-year study was conducted to establish the effects of drip and microsprinkler irrigation systems on populations of Pratylenchus penetrans, early plant growth, and fruit yield of sweet cherry trees planted into soil previously used for apple production. The effects of irrigation type on root colonization by arbuscular mycorrhizal fungi, the abundance of soil microbial antagonists, soil biological suppressiveness, plant nutrition, and soil water content were also evaluated. Trees that received drip irrigation had larger trunk diameters than trees irrigated with microsprinklers throughout the first four years of orchard establishment, with greater total fruit yield also observed with drip irrigation in the fourth growing season. Populations of P. penetrans in soil and roots were smaller under drip irrigation than microsprinkler. Trees irrigated using drip emitters had higher per cent root colonization by arbuscular mycorrhizal fungi than those irrigated by microsprinklers, and had a greater density of fine roots in soil. Drip irrigation also increased soil volumetric water content in the root zone, with soil moisture content often approaching or exceeding field water-holding capacity relative to that of microsprinklers. Overall, drip irrigation shows potential as a component of an integrated pest management strategy for reducing the effect of P. penetrans on newly planted sweet cherry.

Moisture effect on soil humus characteristics in a laboratory incubation experiment

Li C., Gao S., Zhang J., Zhao L., Wang L. (2016): Moisture effect on soil humus characteristics in a laboratory incuba tion experiment. Soil & Water Res., 11: 37–43. A 180-day laboratory incubation experiment (30°C) was conducted to investigate the quantitative and qualitative characteristics of humic fractions in a Mollisol at different moisture conditions. The soil moisture contents were 30, 60, and 250% field water-holding capacity (WHC), which represented the low, middle, and high moisture levels, respectively. The results showed that the carbon contents of the total soil and corresponding humic fractions gener ally decreased with increasing soil moisture. A significant difference was observed between the 250% WHC and the two other moisture levels. By contrast, the carbon content of the water soluble fraction significantly increased with increasing soil moisture levels. The solid-state 13 C nuclear magnetic resonance (NMR) spectra showed that the alkyl C/O-alkyl C, aliphatic C/aromatic C, and hydrophobic C/hydrophilic C ratios were in the order of 250% WHC > 30% WHC ≈ 60% WHC, 30% WHC ≈ 60% WHC > 250% WHC and 250% WHC > 60% WHC ≈ 30% WHC for humic acid, and 250% WHC > 30% WHC ≈ 60% WHC, 60% WHC ≈ 250 % WHC > 30% WHC and 30% WHC ≈ 250% WHC > 60% WHC for humin, respectively. These results indicated that a high moisture level was unfavourable for the carbon accumulation of the total soil and humic fractions, whereas it was favourable for the accumulation of water soluble carbon. Although soil moisture levels had a distinct effect on the chemical composition of humic acid and humin, the decomposition degree of the two humic substances components, as indicated by the alkyl C/ O-alkyl C ratio, were both higher at a high moisture level than at a low moisture level. Therefore, the lower soil organic carbon content at a high moisture level than at a low moisture level can be ascribed to the higher water soluble carbon content and larger decomposition degree of humic acid and humin in the former. Our results are important for understanding the behaviour and mechanisms of humic substances at specific soil moisture conditions.