Gravel Mulching Research Articles

Planting Ages Inhibited Soil Respiration and CO2-C Emissions Attribute to Soil Degradation in Gravel-Mulched Land in Arid Areas

Gravel mulching is a widely employed strategy for water conservation in arid agricultural regions, with potential implications for soil carbon (C) sequestration and greenhouse gas emissions. However, soil respiration and CO2-C emissions remain uncertain owing to less consideration of the influence of precipitation patterns and planting age. In this study, we investigated the soil respiration rate (Rsoil) and cumulative CO2-C emission (Ccum), both measured over a period of 72 h, along with soil properties and enzyme activities under different precipitation conditions based on gravel mulching with different planting ages. We analyzed the effects of planting ages on Rsoil and Ccum and revealed the underlying mechanisms driving changes in environmental factors on Rsoil and Ccum. The results demonstrated that the Rsoil reached the maximum value at about 1 h, 0.5 h, and 0.25 h after rewetting in 1, 10, and 20 years of gravel mulching under the condition with 1 mm, 5 mm, and 10 mm of precipitation, respectively, whereas the Rsoil exhibited its maximum at about 8 h after soil rewetting under precipitation of 30 mm. The Ccum induced by precipitation pulses tends to decrease with increasing years of gravel mulching. The Ccum was 0.0061 t ha−1 in the 20-year gravel-mulched soil, representing a 53.79% reduction compared to the 1-year gravel-mulched soil. Soil organic matter (SOM), planting ages, and alkaline phosphatase (ALP) were the primary factors influencing the Rsoil and Ccum in 0–20 cm, while SOM, planting ages, and soil porosity (AirP) were the key factors affecting the Rsoil and Ccum in 20–40 cm. The Rsoil and Ccum in the 0–20 cm soil were regulated by soil enzyme activities, while those of 20–40 cm soil were controlled by soil properties. This indicates that the decrease in Rsoil and Ccum is caused by soil degradation, characterized by a decrease in SOM and ALP. This study offers a novel insight into the long-term environmental impact of gravel mulching measures in arid areas, which is helpful in providing a theoretical basis for dryland agricultural management. It is imperative to consider the duration of gravel mulching when predicting the potential for C sequestration in arid agricultural areas.

Gravel Mulching Significantly Improves Crop Yield and Water Productivity in Arid and Semi-Arid Regions of Northwest China: Evidence from a Meta-Analysis

In the arid and semi-arid regions of Northwest China, periodic rainfall deficits, high field evaporation, limited freshwater resources, and high irrigation costs restrict crop yield and water productivity (WP). Gravel mulching (GM), a traditional agricultural tillage management practice widely used in arid and semi-arid regions, improves crop yield and WP. However, the combined impacts of GM on crop yield and WP are unclear. This study aimed to examine the effects of GM on crop yield and WP under different factors and to find the most critical regional factors and gravel characteristics that affect crop yield and WP. To quantitatively assess the impact of GM on crop yield and WP, this study performed a meta-analysis, a regression analysis, and a path analysis of 185 yield comparisons and 130 WP comparisons from 30 peer-reviewed scientific reports. This study found that GM significantly increased crop yield and WP by an average of 29.47% and 28.03%, respectively. GM was reported with the highest response percentages (I) of crop yield and WP in regions whose average annual precipitation (AAP) was 200–400 mm, average annual temperature (AAT) was 0–9 °C, and altitude (A) was >1000 m. Overall, AAP, AAT, and A had significant effects on the I of crop yield (p < 0.001), but AAT and A had an insignificant impact on the I of crop WP (p > 0.05). Gravel size (GS), the amount of gravel mulching (AGM), the degree of gravel mulching (DGM), and the gravel mulching thickness (GMT) had a significantly positive impact on crop yield and WP (p < 0.05). The stepwise multiple linear regression analysis results indicated that the primary regional factors influencing yield were AAT and A, contributing 43.14% and 53.09%, respectively. GMT and GS were identified as significant gravel characterization factors impacting yield, contributing 82.63% and 17.37%, respectively. AAP and GMT were the main regional factors and gravel characterization factors affecting WP. Furthermore, the I values for cash crop yield and WP were higher than that for food crops, and moderate fertilization and irrigation would increase the I values of yield and WP. The benefits of GM are strongly correlated with the planting year. This study’s results show that GM generally improves crop yield and WP, although the extent of this impact varies based on different conditions. These findings are not only useful in relation to their direct applicability to other countries worldwide but also due to their potential to provide new ideas for agricultural practices in similar crop-growing environments.

Effect of gravel coverage on the hydrodynamic characteristics of overland flow on the Loess Plateau in China

In the Loess Plateau of China, the presence of gravel mulching is widespread, and investigating the dynamic changes in hydrodynamic properties induced by gravel coverage is crucial for optimizing soil and water conservation in this region. In this study, the effect of gravel coverage on the hydrodynamic parameters characterizing the overland flow was investigated through indoor artificially simulated scouring experiments, considering ten different gravel coverages, four slope gradients, and nine flow discharges. The results demonstrated significant differences in hydrodynamic parameters under various experimental conditions (P < 0.01). The flow depth exhibited a linear increase with increasing gravel coverage. Compared to flow velocity observed on non-gravel-covered slope, the reduction percentage of flow velocity ranged from 13.62 % to 72.4 % on gravel-covered slopes. Furthermore, a prediction model was developed to quantify the impact of gravel coverage on the mean flow velocity of overland flow. The model achieved a high R2 of 0.858 and a low RME of 13.61 %. The experiments revealed that the overland flow was distributed in the “virtual laminar”-subcritical and transitional-supercritical zones, with mutual restrictions between the influence of gravel coverage and slope gradient on the flow regime. Finally, it was observed that the Darcy–Weisbach resistance coefficient increased with an increase in gravel coverage. These findings provide a solid theoretical basis for optimizing soil erosion prediction models based on the hydrodynamic characteristics of overland flow, and offer guidance for the rational allocation of soil and water conservation measures for gravel-covered slopes.

Temporal and Habitat Dynamics of Soil Fungal Diversity in Gravel-Sand Mulching Watermelon Fields in the Semi-Arid Loess Plateau of China.

Mulching is an important agricultural management tool for increasing watermelon productivity and land-use efficiency because it helps improve water use efficiency and reduce soil erosion. However, there is relatively little available information regarding the effects of long-term continuous monoculture farming on soil fungal communities and related fungal pathogens in arid and semiarid regions. In this study, we characterized the fungal communities of four treatment groups, including gravel-sand-mulched farmland, gravel-sand-mulched grassland, fallow gravel-sand-mulched grassland, and native grassland, using amplicon sequencing. Our results revealed that the soil fungal communities differed significantly between mulched farmland and mulched grassland as well as the fallow mulched grassland. Gravel-sand mulch significantly impaired the diversity and composition of soil fungal communities. Soil fungal communities were more sensitive to gravel-sand mulch in grassland than in other habitats. Long-term continuous monoculture (more than 10 years) led to decreased abundance of Fusarium species, which contains include agronomically important plant pathogens. In the gravel-mulched cropland, some Penicillium and Mortierella fungi were significantly enriched with increasing mulch duration, suggesting potential beneficial properties of those fungi that could be applied to disease control. We also found that long-term gravel mulching in continuous monoculture farming could potentially form disease-suppressive soils and alter soil microbial biodiversity and fertility. Our study provides insights into the exploration of novel agricultural management strategies along with continuous monoculture practice to control watermelon wilt disease by maintaining a more sustainable and healthier soil environment. IMPORTANCE Gravel-sand mulching is a traditional agricultural practice in arid and semiarid regions, providing a surface barrier for soil and water conservation. However, application of such practice in monocropping systems may lead to outbreaks of several devastating plant diseases, such as watermelon Fusarium wilt. Our results with amplicon sequencing suggest that soil fungal communities differ significantly between mulched farmland and mulched grassland and are more sensitive to gravel-sand mulch in grassland. Under continuous monoculture regimens, long-term gravel mulch is not necessarily detrimental and may result in decreased Fusarium abundance. However, some known beneficial soil fungi may be enriched in the gravel-mulch cropland as mulch duration increases. A possible explanation for the reduction in Fusarium abundance may be the formation of disease-suppressive soils. This study provides insight into the need to explore alternative strategies using beneficial microbes for sustainable watermelon wilt control in continuous monocropping system.

What drives soil degradation after gravel mulching for 6 years in northwest China?

Gravel mulch is an agricultural water conservation practice that has been widely used in the semi-arid region of northwest China, but its effectiveness is now lessening due to soil degradation caused by long-term gravel mulching. In this study, we report on a 6-year-long gravel mulch experiment conducted in the northwestern Loess Plateau to evaluate the impact of gravel mulch on soil physicochemical properties and microbial communities, with the objective of clarifying the causes of long-term gravel mulching-induced land degradation. After 6 years mulching, we found that gravel mulched soil contained significantly higher concentrations of total carbon and total organic carbon than non-mulched soil (control). Long-term gravel mulching significantly changed the soil microbial diversity and abundance distribution of bacterial and fungal communities. Notably, the relative abundance of Acidobacteria was significantly higher under gravel mulching than the control (no mulching), being significantly greater in the AG treatment (small-sized gravel, 2-5 mm) than all other treatments. Conversely, the relative abundance of Actinobacteria was significantly lower under gravel mulching than the control, being the lowest in the BG treatment (large-sized gravel, 40-60 mm). At the same time, the relative abundance of Bacteroidetes was significantly lower in AG yet higher in BG vis-à-vis the other treatments. Of the various factors examined, on a 6-year scale, the capture of dust by gravel mulch and altered carbon and nitrogen components in soil play major contributing roles in the compositional change of soil microorganisms. These results suggest that modified soil material input from gravel mulching may be the key factor leading to soil degradation. More long-term experimental studies at different sites are now needed to elucidate the mechanisms responsible for soil degradation under gravel mulching.

Evaporation effect of infiltration hole and its comparison with mulching

Reducing ineffective evaporation of soil water is an important way to relieve drought in semi-arid rainfed agricultural areas. An infiltration hole is a supplemental measure for slope rainwater harvesting measure and is commonly used in vegetation restoration and orchard management of slopes. However, the evaporation effects of infiltration holes are unclear. In this study, we determined the evaporation effects of infiltration holes under a high initial soil water content and compared the differences in inhibition of soil evaporation among infiltration holes, mulching, and their combination after a rainstorm event. The results showed that the infiltration holes at different depths increased soil daily evaporation in the first 26 days under the high initial soil water content, after which it decreased. Compared with the control, the average daily evaporation while covering the top surface and the hole (sidewall and bottom) decreased by 74.3% and 4.3%, respectively. After the rainstorm event, cumulative evaporation (97 days) significantly decreased by 42.0% and 34.0% under the infiltration hole compared to gravel mulching and branch mulching, respectively. Overall, the infiltration hole increased soil evaporation at the early stage. Soil water mainly evaporated through the top surface of the soil column rather than through the hole itself. In the long term after rainstorms, infiltration holes have better effects in inhibiting evaporation than mulching. Our findings determine the evaporation effects of infiltration holes in the process of harvesting rainwater to replenish soil water in semi-arid rainfed agricultural areas.

Effects of Surface Mulching on the Growth and Water Consumption of Maize

This study provides understandings of the effect of mulching on the growth, development, and water consumption of dry maize. Parameters including soil temperature, soil water-filled pore space (WFPS), water storage capacity, water consumption, grain yield, water-use efficiency, and biomass yields were followed and analyzed by applying straw mulching (SM), gravel mulching (GM), and plastic film mulching (FM). The results show that the soil temperature (0–20 cm) throughout the whole observation period (2011–2013) was significantly increased by applying GM and FM, while SM reduced the soil temperature. SM increased the WFPS, while FM and GM showed no significant effect. SM and FM increased the soil water storage and water-use efficiency in the early stages of maize growth (from sowing to vegetative growth) compared with using GM. With the progress of time, fewer differences between all treatments were observed. Water consumption of the three treatments was in the order of SM &lt; FM &lt; GM, indicating that SM was the most effective in preventing water evaporation. The resulting yields of corn also varied. Compared with the control, FM significantly increased the yields by 1.7, 0.5, and 2.2 ton/ha in the tested three years, respectively. In contrast, GM showed no significant difference in the three years, and SM showed no significant difference in 2011 and 2012 but increased the yield by 2.2 ton/ha in 2013. FM is shown to be an effective method for increasing the yields of corn for the studied region, GM is not recommended, and SM is the most effective in improving the water availability in the soil, while its effect on corn yields needs to be further explored.

Long-term film mulching with manure amendment increases crop yield and water productivity but decreases the soil carbon and nitrogen sequestration potential in semiarid farmland

Plastic film and gravel mulching in combination with fertilization are widely used to increase crop yields and water productivity (WP) in arid and semiarid areas, but soil surface mulching may stimulate soil organic carbon (SOC) mineralization; therefore, film mulching with manure amendment was proposed to improve soil fertility. However, the combined effects of these practices on yield, WP, and the stocks of SOC and total nitrogen (TN) need to be better understood. This study investigated the long-term effects of different practices on crop yields, WP, and SOC and TN stocks in the 0–20, 20–40 and 40–60 cm layers based on a 12-year spring maize (Zea mays L.) field experiment on the Loess Plateau. The treatments included no mulching + NPK (CK), gravel mulching + NPK (GM), film mulching + NPK (FM), and film mulching + NPK + cow manure (FCM). In 2019 and 2020, compared with the control, both FM and FCM significantly increased crop yields, WP, N uptake efficiency (NupE) and N fertilizer productivity (NfP). Compared with CK, the FCM treatment significantly increased the SOC and TN stocks by 44.10% and 39.51%, respectively, on average, and the minimum C input that could maintain the soil C balance on the Loess Plateau was 0.67 Mg ha−1 yr−1. Over the 12 experimental years, compared with the initial value in 2009, the trends of SOC and TN contents in the FM treatment were downward, while those in the FCM treatment increased by 41.61% and 30.27%, respectively, but yearly input of manure led to SOC equilibrium. Compared with CK, the FCM treatment significantly decreased SOC and TN sequestration potential by 33.38% and 19.59%, respectively, on average in topsoil (0–20 cm), but it had less of an effect on SOC and TN sequestration at 20–40 and 40–60 cm soil depths. The reasons for SOC reaching equilibrium in the FCM treatment were analyzed, and periodic subsoiling was proposed to break the equilibrium state to further improve the sequestration amount of SOC and TN at 0–60 cm soil depths. In conclusion, film mulching with manure amendment was recommended as a long-term strategy to improve soil productivity and soil fertility in semiarid farmland.

Effects of organic fertilizer proportion on the distribution of soil aggregates and their associated organic carbon in a field mulched with gravel

Gravel and sand mulching is an indigenous technology that has been used for increasing soil temperature and improving crop yield and water use efficiency for at least 300 years in northwestern China. However, long-term application of inorganic fertilizer with gravel and sand mulch could decrease the soil organic carbon content, and how to improve soil fertility under gravel and sand mulching remains largely unknown. Thus, we evaluated the effects of the application of inorganic (chemical) and organic (manure) fertilizers on the distribution of soil aggregates and their associated organic carbon in a field mulched with gravel and sand. A 5-year (2014–2018) field experiment was conducted in the arid region of northwestern China. Total organic carbon (TOC), permanganate oxidizable carbon (POC), TOC reserves in soil aggregates with different particle sizes, and watermelon (Citrullus lanatus) productivity in gravel-mulched fields were analysed for the following six fertilization modes: no N fertilizer input as a control (CK), N fertilizer without organic fertilizer (CF), and organic fertilizer replacing 25%, 50%, 75%, and 100% of mineral nitrogen (recorded as OF-25%, OF-50%, OF-75% and OF-100%, respectively). The results showed that, higher manure to nitrogen fertilizer ratios were positively correlated with the percentage of soil macroaggregates (> 0.25 mm), mean weight diameter (MWD), TOC and POC concentrations, and their ratios in different particle sizes. Compared with CF, the treatments with 50% to 100% organic fertilizer significantly increased TOC storage (5.91–7.84%) in the soil profile (0–20 cm). Moreover, the CF treatment did not increase SOC concentrations or TOC storage, compared with CK. The fruit yield (2014–2018) of watermelon significantly increased by an average of 31.38% to 45.70% in the treatments with 50% to 100% organic fertilizer, respectively, compared with CF. Our results suggest that the partial replacement of chemical fertilizer with organic manure (OF-50%, OF-75% and OF-100%) could increase the proportion of macroaggregates, POC and TOC concentrations, and TOC stock in aggregates with different particle size and improve the yield of watermelon in the gravel fields of arid northwestern China mulched with gravel and sand.

Analysis of UV–Vis spectral characteristics and content estimation of soil DOM under mulching practices

Dissolved organic matter (DOM), which is generally expressed in terms of dissolved organic carbon (DOC), is a key indicator used to monitor the short-term dynamics of soil quality. However, its content and molecular composition are strongly influenced by agricultural practices, and the determination of DOC content is cumbersome and expensive. A field experiment with three treatments, including (i) no mulching (CK), (ii) gravel mulching (GM) and (iii) film mulching (FM), was selected to study the content and composition characteristics of DOC under different agricultural practices using ultraviolet visible (UV–Vis) technology. The results showed that the GM and FM treatments significantly decreased the DOC contents in topsoil (0–20 cm) by 6.15% and 12.18%, respectively, in comparison with the control. The FM treatment significantly decreased the values of specific UV absorbance at 254 nm (SUVA254), 260 nm (SUVA260) and Chromophoric DOM (CDOM) in each soil layer, indicating the aromaticity, hydrophobicity and CDOM content in the FM treatment were significantly decreased in each soil layer. To establish an accurate model for rapid determination of soil DOC, Spearman correlation analysis was performed on normally and non-normally distributed datasets, and linear regression analysis was utilized for modeling with normalized data. The results of linear regression analysis showed that the regression models established among CDOM/DOC, CDOM, SUVA254, SUVA260, and specific UV absorbance at 280 nm (SUVA280) had a high degree of fit, with coefficients of determination (R2) all exceeding 0.95. The model validation results showed that the regression model established between CDOM/DOC and CDOM had the highest accuracy with the lowest root mean squared error (RMSE) (3.58 mg kg−1) and the lowest relative error (RE) (2.74%), which was DOC = 58.065 + 184.355 × A(355) mg kg−1. The results showed that the estimation of soil DOC can be achieved with good prediction using UV–Vis technology. This study highlights the potential of UV–Vis spectroscopic technology to rapidly estimate soil DOM in agriculture.

Effects of Different Gravel Mulching on Soil Moisture Status and Regression Model Prediction in Arid Regions

Drought is one of the main factors limiting the agricultural planting and production; gravel mulching is an effective inhibiting evaporation and water-saving planting pattern in the arid regions. In this study, experiments were conducted to study soil moisture effect and regression model with different gravel mulching, the soil moisture content and evaporation were compared that gravel mulched with different particle sizes, different thickness layer and different mulched years. The results showed that: 1) The cumulative soil evaporation of gravel mulched was only 29.3% of that bare fields. Mulching gravel could significantly reduce soil moisture evaporation. 2) The effects of inhibiting soil moisture evaporation are the best when mulch gravel thickness is 10 - 15 cm. 3) The particle size of gravel mulched is smaller, the evaporation inhibition effect will be better. Considering the water holding capacity and material economy, it is the most suitable to mulch gravel with the particle size of 3 - 5 cm. 4) Mulching gravel on the soil surface for 1 - 3 years can improve the soil moisture content. However, the gravel was mulched for more than five years, the soil moisture content decreased significantly. 5) The quadratic polynomial regression fitting model can better simulate and predict the cumulative evaporation on different gravel mulched, and the regression fitting degree R2 is more than 0.98.

The effect of long-term soil surface mulching on SOC fractions and the carbon management index in a semiarid agroecosystem

Soil organic carbon (SOC) and its fractions are widely considered to be valuable indicators for monitoring soil carbon (C) pools and dynamics induced by mulching practices. Thus, a 10-year experiment with three treatments, including no mulching (CK), gravel mulching (GM) and film mulching (FM), was established on the Loess Plateau. The results showed that SOC under GM treatment (7.88 g kg−1) in surface soil (0–20 cm) decreased significantly compared with that of CK (8.59 g kg−1), and that of FM (8.09 g kg−1) did not change significantly. Compared with CK in surface soil, water soluble C (WSC) under FM treatment decreased by 9.36% on average, and hot-water extractable C (HWC) under GM and FM treatments increased by 12.36% and 24.56% on average, respectively. Labile organic C (LOC) determined by the potassium permanganate (P-P) method did not decrease significantly under FM treatment in surface soil, but recalcitrant organic C (ROC), determined by the P–P method, significantly decreased by 9.88% on average. Compared with CK, less labile C (CLL), determined by the modified Walkley-Black (M–W–B) method under GM and FM treatments, significantly decreased by 11.21% and 17.54% on average, respectively, which suggested that CLL was converted to very labile C (CVL) and labile C (CL). This result indicated that the M-W-B method was superior in explaining C turnover. Combined with the C management index (CMI) results of previous studies, CMI was consistently lower under GM treatment, and it was unstable under FM treatment. The sensitivity index (SI) results indicated that HWC was the most sensitive SOC fraction, and LOC and ROC determined by the M–W–B method were more sensitive than those determined by the P–P method. Moreover, CMI calculated by the M–W–B method (10–35%) was more sensitive than that calculated by the P–P method (9–12%). In conclusion, the decrease in SOC under long-term mulching is mainly from ROC, and the M–W–B method is superior to the P–P method.

Effect of using an infiltration hole and mulching in fish‐scale pits on soil water, nitrogen, and organic matter contents: Evidence from a 4‐year field experiment

AbstractSoil water, nitrogen, and organic matter contents are among the main limiting factors for successful vegetation restoration on degraded slopes in arid and semi‐arid areas. Combining slope engineering measures for revegetation is considered an effective eco‐rehabilitation practice used to restore degraded slopes. However, a single slope measure is insufficient to efficiently utilize runoff and sediments to improve soil water, nitrogen, and organic matter for revegetation. In this study, four treatments were implemented on a hilly slope in a temperate continental semiarid area slope engineered with fish‐scale pits (semicircle‐shaped pit, 1.0 m in diameter, 0.5 m in radius, and 0.2 m deep), namely: with gravel mulching (GM), straw mulching (SM), infiltration hole (IH), and without other measures (CK). The effects of the combined measures on soil water, nitrogen, and organic matter contents were analyzed over 4 years. The results showed that the soil water storage (0–100 cm) showed no significant differences among all treatments; however, the soil (100–260 cm) of GM/SM/IH treatment increased by 11.65%/8.62%/7.10% compared with CK (p &lt; 0.05). The soil organic matter and nitrogen (0–100 cm) under IH were 73.34%/81.29%/98.32% and 77.37%/80.27%/85.31% higher than CK/SM/GM, respectively (p &lt; 0.05). Overall, IH is the most effective measure for increasing nitrogen and organic matter, and it is equally effective with GM and SM to increase the water replenishment of deep soils in semiarid areas. Our findings provide the combined measures to combat soil water, nitrogen, and organic matter deficits for slope revegetation in arid and semiarid areas.

Experimental study of mulching effects on water restoration of deep, desiccated soil in a loess hilly region

ABSTRACT Drought climate and human activity have led to serious soil desiccation in the loess hilly region. Mulching measures can effectively increase rainfall infiltration and reduce evaporation, thus improving soil moisture status. The objective of this study was to explore the characteristics of water restoration of deep desiccated soil under different mulching measures and determine a promising mulching measure. We built large-scale simulation desiccated soil columns in the field (soil columns with an 0.8-m diameter and 10-m depth). Six kinds of treatments were tested: film mulching, gravel mulching, branch mulching, planting of jujube tree (Ziziphus jujuba Mill.) and robinia (Robinia pseudoacacia L.), and bare land as the control. The results showed that different mulching measures can increase soil water storage and alleviate the soil drying phenomenon to different degrees. Compared with other treatments, film mulching is more effective, with larger increment of soil water storage, deeper restoration of soil dry layer, and simple to operate in loess hilly region. So, we recommend film mulching, which is a feasible method to improve the soil desiccation status in hilly loess areas.

Runoff and soil and nutrient losses from gravel mulching: A field experiment with natural rainfall on the Loess Plateau of China

Gravel mulch has been used effectively to conserve agricultural water for three centuries in the semiarid Loess Plateau of northwestern China. In this study, gravel mulch field experiments on the slopes of the plateau were carried out to evaluate the effects of different particle sizes of gravel mulch and different slope gradients on surface runoff, soil erosion, and nutrient losses under natural rainfall throughout 2017 and 2018. Experiment plots (3 m × 5 m) on slopes of 5°, 10°, 15°, and 30° were implemented; in each plot, three gravel mulch treatments were investigated: fine gravel (2 to 5 mm in size, FG), coarse gravel (40 to 60 mm, CG), and the control that lacked any mulching (CK). We found that gravel mulching on soil significantly reduced both the amounts of runoff and soil loss under natural rainfall conditions in 2017 and 2018, for which the soil loss-suppression effect was most pronounced under FG mulching. Applying FG also significantly increased the rainfall threshold to generate runoff, and caused the fewest runoff events during the two years of monitoring. Coarse gravel mulching caused a strong reduction in soil loss on the relatively flat slopes (i.e., 5° and 10°) whereas its effect was weak on relatively steep slopes (i.e., 15° and 30°). The respective effects of FG and CG mulching on the losses of various nutrients from soil also differed markedly. The gravel mulching significantly increased the amounts of total nitrogen (TN), potassium (K), and nitrate-nitrogen (NO₃-N) in the runoff but greatly decreased those of iron (Fe), copper (Cu), and zinc (Zn). Furthermore, the amount of nutrients lost in runoff increased with a steeper slope, with notably greater variability of nutrient elements in the runoff on the steepest slopes. Accordingly, FG mulching is recommended for use in arid and semiarid areas from the perspective of water, soil, and nutrient conservation.

Effects of gravel-sand mulch on the runoff, erosion, and nutrient losses in the Loess Plateau of north-western China under simulated rainfall

Gravel mulching is a characteristic agricultural technique that has been used for hundreds of years in the north-western Loess Plateau of China. However, the effects of the gravel-sand mulch on the processes of the runoff, soil erosion, and nutrient losses are neither fully distinguished nor even known in many parts of the world. This study investigated how different gravel particle sizes in the mulch affected the runoff, erosion as well as the extent of the nutrient losses in the surface runoff. The laboratory experiments were conducted using a rainfall simulator with three gravel mulch treatments: (1) fine gravel mulch (FG); (2) medium gravel mulch (MG); (3) coarse gravel mulch (CG) and a control group, bare soil (BS). The results of these rainfall simulation experiments gave estimates on how the grain size influences the runoff and losses of the soil and its nutrients. Applying the gravel mulch significantly delayed the runoff’s starting time when compared with the bare soil. Both the total runoff and soil loss increased with the grain size of the gravel mulch. Compared with the bare soil, the lowest surface runoff and soil loss was observed from the fine gravel treatment. These results clearly show that gravel mulch plays an important role in the runoff and sediment generation processes, and that it significantly reduces the surface runoff and soil loss. The losses of the total nitrogen (TN), total phosphorus (TP), and total organic carbon (TOC) from the bare soil were much higher than those under the gravel mulching. The fluctuations in these nutrient-loss processes were the most intense in the CG treatment, while the TC content, in initial runoff, was significantly higher in the FG than the other treatments. Our findings suggest gravel mulch is a useful water and soil conservation technique in the loess area of north-western China, and these results can inform one on the theoretical principles for properly utilising gravel-mulched fields.

Water harvesting techniques for improving soil water content, and morpho-physiology of pistachio trees under rainfed conditions

Water harvesting techniques have shown promising outcomes in mitigating risks, increasing yields and delivering positive influences on other ecosystems. A field study was conducted in Northern Jordan to assess the influence of combined in-situ water harvesting techniques, micro-catchment and mulching on soil moisture content, plant morphology, gas exchange [photosynthesis (Pn), transpiration (E), and stomatal conductance (gs)] and midday stem water potential (Ψsmd) of young pistachio (Pistacia vera cv. Ashori) trees. Four mulching treatments [straw, vertical gravel, horizontal gravel and control (no mulching)] and three micro-catchment areas (36, 64 and 100 m2) were used. Pistachio trees were grown under rainfed conditions for two growing seasons. Gravel mulching (vertical and horizontal) and 36 m2 micro-catchment had the highest percentage increase in plant height compared with other treatments. In addition, 36 m2 micro-catchment significantly increased gas exchange variables (Pn, gs, and E). We partially attributed that to higher soil water content and Ψsmd in the 36 m2 compared with 64 and 100 m2 micro-catchment. Interestingly, the runoff water collected from 36 m2 treatment was 75 % higher than 64 m2 (53.4 vs. 30.6 L) and 28 % higher than 100 m2 (53.4 vs. 41.7 L). Therefore, the 36 m2 is the best micro-catchment area in term of runoff efficiency. Overall, the combined water harvesting techniques, gravel mulching (vertical and horizontal) and the 36 m2 micro-catchment hold promise for improving the morphology and physiology of young pistachio trees grown under rain-fed regime.

Effects of Embedded Gravel or Gravel Mulching in Southern Red Soil on Slope Sediment Yield and Runoff

Effects of Embedded Gravel or Gravel Mulching in Southern Red Soil on Slope Sediment Yield and Runoff

Cultivation and mulching materials strategies to enhance soil water status, net ecosystem and crop water productivity of winter wheat in semi-humid regions

Different cultivation practices with mulching materials have been applied in the semi-arid areas of China. However, there is still insufficient systematic research on its eff ;ects on ecological indexes and crop water productivity. Therefore, a field trial was carried out in three consecutive study years (2015–2018) to evaluate ecological productivity, crop water productivity, and wheat production under six different treatments: CT: conventional flat tillage without mulching; TSM: conventional flat tillage with gravel mulching; TPM: conventional flat tillage with plastic film mulching; RP: ridges covered with plastic film and furrows without mulching; RSM: ridges covered with plastic film and furrows with gravel mulching; RPM: ridges and furrows covered with plastic film mulching. We found that different cultivation and mulching materials practices considerably improved soil moisture content, crop productivity, ecological eff ;ects and evapotranspiration (ET) rates. The RP cropping system with different mulching practices significantly increased soil moisture and ecosystem CO2 and NO2 emissions during the three consecutive study years. The RP cropping system with gravel or plastic film mulching on the furrows improved the dry matter per plant and LAI at the late growth stage, and it improved crop water productivity. Compared to the CT cultivation practice, the annual net primary productivity (NPP) and net ecosystem productivity (NEP) were significantly increased by 13% and 70%, respectively, with the RPM. In the RPM treatment, the CWPeco and CWPyield were significantly improved by 66% and 84%, respectively, relative to the CT cultivation practice. In addition, RPM treatment improved the spike partitioning index by 16%, maintained a fruiting efficiency that was 12% higher, increased water soluble carbohydrates (WSC) in the stem, increased apparent translocation (amount and ratio), and ultimately achieved an 89% higher grain yield. Taking into account the ecological eff ;ects, wheat production and ET rate, RPM treatment is an eff ;ective approach for saving water and improving CWP and production in semi-humid conditions.

Plastic-soil mulching increases the photosynthetic rate by relieving nutrient limitations in the soil and flag leaves of spring wheat in a semiarid area

The stoichiometric characteristics of plants are significantly affected by soil nutrients and moisture, which regulate photosynthesis. In wheat, they can be assessed to determine environmental adaptability. The selected spring wheat was investigated in a field experiment conducted from 2015 to 2017 in a semiarid area. The three treatments were (1) plastic-soil mulching (PMS), (2) gravel mulching (SM), and (3) without mulching (CK). The soil chemical properties and the net photosynthetic rate in flag leaves were recorded; the stoichiometric parameters of soil and flag leaves were calculated. The soil organic carbon (C) of PMS increased significantly in the 0–30-cm profile when compared with SM and CK, respectively. The soil nitrogen (N)/phosphorus (P) ratio of PMS increased in the filling stage when compared with SM and CK, respectively. The C/N ratio in flag leaves of wheat under PMS significantly decreased and increased compared with SM and CK at the filling stage during a wet year, respectively, and significantly decreased compared with CK during a drought year. The C/N and C/P ratios were significantly correlated between soil and wheat flag leaves in SM, and the net photosynthetic rates and the C/N, C/P, and N/P ratios of flag leaves under PMS and SM were also significantly correlated. The PMS treatment relieved soil nutrient limitations in flag leaves and increased the net photosynthetic rate by optimizing foliar C/N, C/P, and N/P ratios. This resulted in increased photosynthesis under drought conditions and significantly increased the yield and water-use efficiency.