Ridge Soil Research Articles

Ridge with no-tillage facilitates microbial N2 fixation associated with methane oxidation in rice soil

Aerobic methane-oxidizing bacteria (MOB) play a crucial role in mitigating the greenhouse gas methane emission, particularly prevalent in flooded wetlands. The implementation of ridge with no-tillage practices within a rice-rape rotation system proves effective in overcoming the restrictive redox conditions associated with waterlogging. This approach enhances capillary water availability from furrows, especially during periods of low rainfall, thereby supporting plant growth on the ridges. However, the microbe-mediated accumulation of soil organic carbon and nitrogen remains insufficiently understood under this agricultural practice, particularly concerning methane oxidation, which holds ecological and agricultural significance in the rice fields. In this study, the ridge and ditch soils from a 28-year-old ridge with no-tillage rice field experiment were utilized for incubation with 13C-CH4 and 15NN2 to estimate the methane-oxidizing and N2-fixing potentials. Our findings reveal a significantly higher net production of fresh soil organic carbon in the ridge compared to the ditch soil during methane oxidation, with values of 626 and 543 μg 13C g−1 dry weight soil, respectively. Additionally, the fixed 15N exhibited a twofold increase in the ridge soil (14.1 μg 15N g−1 dry weight soil) compared to the ditch soil. Interestingly, the result of DNA-based stable isotope probing indicated no significant differences in active MOB and N2 fixers between ridge and ditch soils. Both Methylocystis-like type II and Methylosarcina/Methylomonas-like type I MOB catalyzed methane into organic biomass carbon pools. Soil N2-fixing activity was associated with the 15N-labeling of methane oxidizers and non-MOB, such as methanol oxidizers (Hyphomicrobium) and conventional N2 fixers (Burkholderia). Methane oxidation also fostered microbial interactions, as evidenced by co-occurrence patterns. These results underscore the dual role of microbial methane oxidation – not only as a recognized sink for the potent greenhouse gas methane but also as a source of soil organic carbon and bioavailable nitrogen. This emphasizes the pivotal role of microbial methane metabolism in contributing to soil carbon and nitrogen accumulation in ridge with no-tillage systems.

INVESTIGATION OF CALIFORNIA BEARING RATIO VALUE OF BAMA RIDGE SOIL ADMIXED WITH METAKAOLIN

The study focused on assessing the impact of Metakaolin on the properties of Bama Ridge Soil in the Maiduguri region and its environs. Soil samples, collected using a disturbed sampling method from two distinct locations, were transported to the laboratory in polythene bags to prevent moisture loss. According to the American Association of States Highway and Transport Officials (AASHTO) and the Unified Soil Classification System (USCS), the soil was classified as A-3(0) and CL. The California Bearing Ratio (CBR) values ranged from 19.23% to 26.66% for soaked conditions and 25.01% to 32.46% for un-soaked conditions, indicating its suitability as sub-grade material. The study suggested that a 15% Metakaolin content would suffice for lightly trafficked roads. However, caution was advised against using the soil as sub-base material for roads with heavy traffic density, as CBR values slightly exceeded 30%. This implies that while the soil shows promise for specific construction applications, it may not be optimal for handling the substantial loads associated with high traffic volumes.

Topography-driven differences in soil N transformation constrain N availability in karst ecosystems

Fragile karst ecosystems are characterized by complex topographic landscapes associated with high variations in vegetation restoration. Identifying the characteristics and driving factors of nitrogen (N) availability across the topographic gradient is essential to guide vegetation restoration in karst regions. In this study, we collected soil samples and plant leaves along the topographic gradient (ridge, upper slope, middle slope, and foot slope) of convex slopes in the karst fault basin of southwest China, and determined the indicators reflecting soil N availability, N transformation rates, and their controlling factors. Our results showed that foliar N content and δ15N value, soil inorganic N content and δ15N value, and foliar N:P ratio were substantially lower on the steep hillslopes than on the flat top ridge. Steep slope soils also had a lower enzyme C:N ratio but a higher enzyme N:P ratio than the flat ridge soils. Furthermore, the vector angles calculated by soil extracellular enzyme analysis were below 45o in all studied soils and decreased significantly with increasing slope, indicating that microbial growth was generally limited by N. These results jointly suggest the declines in soil N availability across the topographic gradient, which are further explained by the changes in soil inherent N transformation processes. As the slope became steeper, soil mineralization and autotrophic nitrification (ONH4) rates decreased significantly, while ratio of microbial NH4+ immobilization to ONH4 and NH4+ adsorption rate increased significantly, indicating the decrease in soil inorganic N supply capacity. We further found that deteriorated soil structure, decreased soil organic matter and calcium content, altered microbial abundance, and increased ratios of fungi to bacteria and gram-positive bacteria to gram-negative bacteria were the primary drivers of reduced N transformation rates and N availability across the topographic gradient. Overall, this study highlights the critical role of the topography in controlling soil N availability by regulating N transformation processes in karst regions. The topography should be considered an important factor affecting the functions and services of karst ecosystems.

Optimization of macronutrient and micronutrient concentrations in roots and leaves for Florida HLB-affected sweet orange trees

Florida sweet orange production has declined largely due to Huanglongbing (HLB) disease. The causative agent, Candidatus Liberibacter asiaticus (CLas) bacteria, lowers tree performance by reducing water and nutrient uptake. HLB-affected trees have a fibrous root density loss of about 30 to 50%, which increases as HLB symptoms develop in the canopy. Currently, no guidelines exist for optimal nutrient concentrations in citrus roots. This study aimed to develop root nutrient and fertilization guidelines for HLB-affected sweet orange trees. The research was conducted on two sites with 5- to 6-year-old ‘Valencia’ sweet orange trees grafted on ‘Swingle’ rootstock. The two sites were representative of the different soil characteristics of the state of Florida, namely Ridge and Flatwood regions. Seven treatments were tested using a randomized complete block design. The Ridge soils site has a high density of trees of about 1359 trees ha−1 while the Flatwoods soils site of southwest Florida has a lower tree density of about 716 trees ha−1. The experiment began in May 2019 and concluded in May 2021. Foliar, root and soil samples were collected from both sites twice a year and nutrient concentrations were analyzed. No significant patterns were observed; however, differences in soil nutrients were found between sites. The obtained data represent trends that could become significant over a longer-term study which encompasses the two different citrus-growing regions in Florida. These lengthier trials are especially needed in the age of HLB in order to curb the declining citrus production.

Soil ridging combined with biochar or calcium-magnesium-phosphorus fertilizer application: Enhanced interaction with Ca, Fe and Mn in new soil habitat reduces uptake of As and Cd in rice

Reducing the bioavailability of both cadmium (Cd) and arsenic (As) in paddy fields is a worldwide challenge. The authors investigated whether ridge cultivation combined with biochar or calcium-magnesium-phosphorus (CMP) fertilizer effectively reduces the accumulation of Cd and As in rice grains. Field trial showed that applying biochar or CMP on the ridges was similar to the continuous flooding, which maintained grain Cd at a low level, but grain As was reduced by 55.6%, 46.8% (IIyou28) and 61.9%, 59.3% (Ruiyou 399). Compared with ridging alone, the application of biochar or CMP decreased grain Cd by 38.7%, 37.8% (IIyou28) and 67.58%, 60.98% (Ruiyou399), and reduced grain As by 38.9%, 26.9% (IIyou28) and 39.7%, 35.5% (Ruiyou 399). Microcosm experiment showed that applying biochar and CMP on the ridges decreased As in soil solution by 75.6% and 82.5%, respectively, and kept Cd at a comparably low level at 0.13–0.15 μg L−1. Aggregated boosted tree (ABT) analysis revealed that ridge cultivation combined with soil amendments altered soil pH, redox state (Eh) and enhanced the interaction of Ca, Fe, Mn with As and Cd, which promoted the concerted reduction of As and Cd bioavailability. Application of biochar on the ridges enhanced the effects of Ca and Mn to maintain a low level of Cd, and enhanced the effects of pH to reduce As in soil solution. Similar to ridging alone, applying CMP on the ridges enhanced the effects of Mn to reduce As in soil solution, and enhanced the effects of pH and Mn to maintain Cd at a low level. Ridging also promoted the association of As with poorly/well-crystalline Fe/Al and the association of Cd on Mn-oxides. This study provides an effective and environmentally friendly method to decrease Cd and As bioavailability in paddy fields and mitigate Cd and As accumulation in rice grain.

Soil properties and tree growth at medieval ridge and furrow sites in Brandenburg, northeastern Germany

AbstractBackgroundRidge and furrow (RIFU) systems and associated soils are a widespread legacy of medieval agriculture, are archives of historical land use, and might affect recent ecosystems. Open questions about RIFU formation and potential legacy effects still exist, especially related to physical soil properties.AimsOur aims were (1) to characterize the soil properties of RIFU soils and (2) to compare the drought sensitivity and the growth resistance in extremely dry years of trees growing on ridges and furrows, respectively.MethodsWe studied soil physical (bulk density, saturated soil hydraulic conductivity, and texture) and chemical (soil pH, soil organic matter, and nitrogen content) properties and the climate sensitivity of tree growth on RIFU systems for three study sites in Prignitz, Germany.ResultsRIFU systems showed a high spatial heterogeneity of soil stratigraphy due to ridge construction and increased accumulation of soil moisture and organic matter in furrows due to post‐abandonment pedogenesis. Slight spatial differences in soil physical properties were found, with increased air capacity in ridge soils and higher available water contents in furrow soils. No differences in drought sensitivity were observed for trees growing on ridges and furrows, except for a wet site, where trees in furrows showed a higher sensitivity. Resistance in dry years tended to be similar or increase from furrows to ridges.ConclusionsThe results reflect a spatial differentiation of stratigraphy and post‐abandonment pedogenesis on abandoned RIFU systems and suggest an adaption to different moisture conditions through RIFU construction. Differences in drought sensitivity of tree growth with relative land surface could only be detected for one of the three sites, where trees were found to be less drought sensitive on ridges.

Granulometric composition of the finite moraine ridge soils of the Upper Volga postglacial region (East European plain, Tver region)

At the experimental field of VNIIMZ (Tver region, village Emmauss) laid a series of 8 soil sections. The first three sections of the southern slope are confined to the transit-accumulative, transit and eluvial-transit microlandscape with a complex of gleevate and gleev soils, which changes to an eluvial-accumulative flat-topped section and similar microlandscapes of the northern slope with slightly bent and gleevate sod-podzolic light loamy soils. In samples taken every 10 cm, the particle size distribution of soils was determined by laser diffraction and sieve (>0.25 mm) methods. The differential distribution curves of soil particles are dominated by fractions of fine sand with a maximum content of diameters of 100–150 µm and silt (1–50 µm). Three granulometrically homogeneous layers are distinguished in the soil profile: the upper one with an arable horizon (0–40 cm), medium (up to 70–80 cm) and super-moraine (up to 120 cm). In the middle part of the soil profile of the northern slope, silty fractions prevail; and in the soils of the southern part of the landscape, a relatively high content of the sandy fraction is observed (the fraction of fine sand, 50–250 µm, dominates, and followed by the coarse silt fraction, 10–50 µm), which, apparently associated with the historical processes of profiles development on binary deposits, erosion, and, possibly, with modern agrotechnological processes.

Design and experiment of the components for soil flow direction control of hilling machine based on EDEM

Cultivation and hilling are important steps in crop field management and provide an important guarantee of crop quality and quantity. With the aim of addressing how the soil flow direction of a traditional cultivation and hilling machine is difficult to control, and because it is difficult to achieve high ridge soil cultivation, among other issues, the components of the soil flow direction control of a hilling machine was designed. The components of the soil flow direction control consisted of a soil-feeding plough device, spiral knives and guide cover devices, etc. The design and analysis of the guiding parts for the two tools of the soil-feeding plough device and the spiral knife were performed to obtain an appropriate guide wall and helix angle. The guiding principle in the flow direction control components was analyzed. The design of the guide wall adopts the torsional columnar plough surface, and the elementary line angle changes from stable to increasing. The analysis of spiral milling showed that when the spiral angle is large, the milling effect is better. According to the discrete element method, the working part of the machine-soil interaction model was established. EDEM software was used to simulate the control components for the soil flow direction of the hilling machine for compound cutting. The design method with a two-factor comprehensive test was used to study the linear velocity along the outer part of the spiral knife and the influence of the forward velocity of machine of the implement on the soil cultivation effect. The results of the discrete element simulation showed that both the linear velocity along the outer part of the spiral knife and the forward velocity of the machine have extremely significant effects on the transportation of particles to the ridge top and the hilling thickness. Following multiple comparisons of the average hilling thickness with different linear velocities along with the outer spiral knife and different forward velocities of the machine, it is concluded that the performance of the machine is better when the linear velocity along the outer spiral knife is 3.01 m/s and the forward velocity of the machine is 0.7 m/s. The research conclusion had great theoretical value and practical significance for the design of the machine, which worked for cultivation and hilling. Keywords: compound cutting, hilling machine, flow direction control, discrete element method, design DOI: 10.25165/j.ijabe.20221503.5857 Citation: Tong Z W, Li L H, Zhang X L, Chen Y, Liu X C, Zhou P L, et al. Design and experiment of the components for soil flow direction control of hilling machine based on EDEM. Int J Agric & Biol Eng, 2022; 15(3): 122–131.

Theoretical Substantiation of the Traction Resistance of the Ridge Seeder

The analysis of the current state of the enterprises of the agro-industrial complex of Russia has shown that various energy-saving cultivation technologies of agricultural crops, including row crops on ridges, are being applied on a large scale. Mainly, such technologies imply a reduction in the number of technological operations performed, the replacement of sowing on pre-treated soil with sowing according to minimal technology or no-till at all. When implementing comb sowing of row crops, the problem of energy saving remains relevant. Keeping in mind the design features and the operation principle of tillage rollers, it can be stated that they are designed mainly for the destruction of soil lumps and compaction of soil on a flat field before or after sowing. There is a problem of high-quality rolling of soil ridges formed simultaneously with the sowing of row crops. (Research purpose) The research purpose is to substantiate the traction resistance of a roller aggregated with a combed roller theoretically. (Materials and methods) The algorithms used to assess the quality of the rollers are imperfect, for reliable justification of the optimization parameter, it is necessary to solve a number of issues, in particular, the methodology for determining the traction resistance of rollers designed for the final creation of soil ridges by simultaneous action of spherical disks and conical wheels on their sides. A skating roller has been developed for the finishing operation of forming a soil ridge with the required parameters and density simultaneously with sowing, the novelty of which is confirmed by patents of the Russian Federation No. 194330, No. 194348, No. 196712. (Results and discussion) The article presents the process of forming a soil ridge by a roller, and the justification of the traction resistance of a ridge drill roller. A vertical load artificially created by a spring additionally acts on the roller of the comb seeder, this load evenly spreads to the conical core and spherical disks of the roller. (Conclusions) The total traction resistance of the roller of the comb seeder is affected by the weight of the conical wheel, frame, additional spring compression load, the size of the rolling wheel and spherical discs, the speed of the roller, as well as the physical and mechanical properties of the soil.

Substantiation of the Density of the Soil Formed by a Ridge Drill Roller

A method is presented for determining the density of soil in the ridge from the simultaneous action of spherical disks and a conical roller wheel. Heuristic and technical analysis of the process of forming soil ridges by rollers made it possible to conclude with a 90 % reliability that the main factorsб which significantly affect the quality of soil ridge formation, are the angle of attack of spherical discs (α = 10°), the speed of the roller (vс = 5.4 km / h) and the compression force of its spring (Fspr. = 180 N).

Processes and rates of formation defined by modelling in alkaline to acidic soil systems in Brazilian Pantanal wetland

Within a soil system, it is generally difficult to relate the observed secondary phases and their spatial distribution to past or current processes. Geochemical modelling can help to identify present-days processes and to quantify formation rates if the system is sufficiently constrained. Here we used the PHREEQC model for this purpose, applying it to soil alkaline to acidic soil systems in the Nhecolândia area. A large amount of data was available, but scientific questions remained opened. We carried out a complementary field study to clarify a key point necessary for modelling, confirming the disconnection between two types of groundwater, perched, alkaline and deep, acidic. Our simulations showed that the observed soil system corresponds to the current biogeochemistry and that paleoclimatic genetic hypotheses are unnecessary. We found that the ridge soil formation rate ranges from 396 to 638 kg ha−1 y−1, depending on hypotheses. We showed that the downslope soils act as buffers to store labile species during the dry season, allowing alkalinity to be maintained from one year to the next. At least 125 y were necessary to obtain downslope alkaline lakes, and this alkaline nature can quickly disappear after changing drainage conditions. We explained how hyperacidic horizons (pH < 4) can neighbor alkaline horizons (pH > 10) with a sharp contact. When correctly informed, geochemical modelling appeared as an effective tool to answer questions about soil processes.

Effect of Tillage on Agro-morphological Parameters and Yield of Cassava (Manihot esculenta crantz) in Abongoua, East-Central Côte d'Ivoire

The objective of this work is to improve the production and yield of cassava cultivated by tillage. The experiment was conducted in the field for 13 months (June 2019-july 2020) in Abongoua in the department of Bongouanou (East-central Côte d'Ivoire). After the cleaning of a 900 m2 surface of a fallow of more than 5 years, and cleared of all plant debris, soil samples were taken with an auger in the 40 cm surface in each corner and in the center of the experimental plot to constitute the composite sample for laboratory analysis. The trials were conducted in a randomized complete block design with four replicates in which four elementary plots were distributed. Three treatments T1 (tilled soil), T2 (mounded soil) and T3 (ridged soil) compared to a control treatment T0 (no-till soil) were applied in each microplot. The cuttings were directly sown at a rate of 12 cuttings per treatment. The data of the different parameters collected underwent an analysis of variance (ANOVA) performed with SAS software version 9.4 and the means were separated using the Newman and Keuls test at the 5% probability threshold. The results showed an acidic soil with a sandy texture and a good supply of nutrients, particularly major elements, trace elements and clay-humus complex. Good growth and development of agro-morphological parameters as well as yield were obtained with treatments T3 (ridged soil), T2 (mounded soil) and T1 (tilled soil) in decreasing order of importance compared to the control treatment (T0). In conclusion, the study clearly showed that the type of tillage, particularly the ridged tillage technique, improves the agro morphological parameters, productivity and yield of cassava. What we recommend to farmers for a good yield of cassava in the area.

Impacts of soil and water conservation practices after half of a generation age, northwest highlands of Ethiopia

Soil and water conservation practices (SWCPs) have been implemented in many parts of Ethiopia for the past 4–5 decades, however, farmers’ are destructing the constructed SWCPs claiming lack of short-term benefits like minimizing slope gradient, reducing soil erosion, improving soil fertility and consequently increasing crop productivity. The aim of this study was to investigate the impacts of SWCPs age on maize grain yield, sediment trapping, soil moisture conservation and slope gradient change in Koga catchment, in the northwest highland of Ethiopia. Physical (fanya juu and soil bund) and biophysical (fanya juu integrated with grass) SWCPs were investigated using field experiment. SPSS version 24 software was used for data analysis. Three treatments were designed in three replications: (i) Fields treated with Fanya Juu (FJ), (ii) Fields treated with soil bund (SB), and (iii) Fields treated with a combination of FJ and Grass (G). The investigated SWCPs were grouped into three age classes (<5 years, 5−10 years and >10 years). The result shows that significantly higher maize grain yield was recorded in fields treated with aged SWCPs than recently constructed SWCPs. Maize grain yield was also higher in fields treated with biophysical SWCPs than fields treated with physical SWCPS alone. Unlike aged SWCPs, significantly higher amount of sediment was recorded behind recently constructed SWCPs because of soil erosion from the newly constructed unstable soil ridges in addition to soil erosion from upslope fields. The sediment trapping efficiency of SWCPs decreases as age increases, because the area of sediment deposition was filled by sediment due to lack of maintenance. Aged SWCPs significantly reduced slope gradient due to the long year trapped sediment and man-made ridge lines made during construction. In general, although the investigated SWCPs improved crop grain yield, maintained soil moisture and reduced slope gradient; the effects were insignificant compared with expectations after 4–5 decades. For instance, slope gradient didn’t change to its minimum. Hence, researchers and experts are expected to develop alternative approaches like ‘’Slope Reversing Terrace (SRT)’’ or modify the existing practices, after half of a generation age experience.

Variation of soil carbon accumulation across a topographic gradient in a humid subtropical mountain forest

Topography is tightly coupled with soil organic carbon (SOC) cycling in sloping landscapes. However, we know little about the spatial variation of SOC accumulation and persistence along a topographic gradient and the controlling processes. Here, we assessed the spatial variation of SOC and its composition along a topographic gradient in a humid mountain forest. The variables associated with environmental factors, topographical traits, carbon input from plants, and soil physico-chemical properties were analyzed to assess their contributions. Results showed that both SOC and mineral-bound organic carbon (MOC) contents were comparable among the topographic positions (ridge, middle slope, lower slope and valley). However, particulate organic carbon (POC) content decreased significantly from ridge to valley. Our measured environmental variables explained 67%, 74% and 77% of the variations in SOC contents for 0–10 cm, 10–20 cm and 20–40 cm soils, respectively. Soil physico-chemical properties (including pH and soil reactive Fe/Al oxides) were the main driver on SOC and MOC variations. In contrast, the variation in POC was more explained by topographical traits and carbon input. We also observed significantly lower SOC stability for ridge soil than valley soil. The significant topographic patterns for SOC fraction and SOC stability suggested that the soil carbon cycling processes were dependent on landscape positions. Future carbon budget and carbon dynamic researches in the humid sloping landscapes should take into account the topographic effects, especially for the free and light carbon fractions.

Process modeling of the first inter-row cultivation in laboratory conditions

The paper considers the formation process of secondary soil ridges by working bodies with flat discs during the first mechanized interrow cultivation of crops in laboratory conditions. Taking account of the agrotechnical requirements and the physical and mechanical properties of the soil, we adopted the reference profile of the soil ridge formed during mechanized inter-row cultivation of crops, which can conditionally be accepted as ideal, as well as the original optimization criterion kсэ1 . After practical implementation of studies in the tillage bin and statistical processing of the obtained data, the corresponding equations were obtained in which the independent process factors were expressed in natural and encoded values. It was found that a change in the speed of a cultivator within 1.2 2.4 m / s, with angles of attack&gt;кk of flat discs from 5º to 20º, increases the distance at which the soil is thrown off and the thickness of the soil layers covering the sides and the upper base of the primary ridge (kсэ1 → max). At angles of attack&gt;кk of flat discs within the limits of 25º ... 30º and the speed of the cultivator from 1.2 m / s to 1.6 m / s, an increase in the thickness of the covered soil layers hпр, occurs, and the coefficient kсэ1 is maximum ((kсэ1 = 0.98 with a flat disc diameter of 0.3 m).

Effect of the Soil Amendments on the Physical and Chemical Properties of the Soil under Centre Pivot Irrigation System

A field trial was conducted to evaluate the application of four soil amendments: sand, gypsum, cow manure and granular sulfur to improve the soil conditions under center pivot irrigation system to manage the mechanization of potato crop harvest in the autumn of 2012; the application of sand amendment was to facilitate mechanical harvest. Evaluation on the improvement of the soil properties were carried out during the growing season through monitoring the changes on soil texture and structure, saturation percentage, bulk density, soil pH and soil salinity. Clods formation occurred at all of the treatments at the harvest time an indication of negative structure improvement due to field trafficking for soil ridging, and spraying during the growing season. The clods samples contained higher %calcium carbonate and higher level of % (Silt+Clay) and less %sand than normal soil samples. Bulk density in the sand treatment was 1.41 gram/cm3 which was significantly higher than the other treatments which ranged 1.13 - 1.19 gram/cm3. Saturation percentage increased at all of the treatments over the period of the experiment from 21 to 31 an indication of significant improvement on the soil water holding capacity. Salinity as measured by the soil Ec was significantly increased over the period of the experiment due to fertilizer application, and salinity at the cow manure treatment was higher than other treatments due to high salt level in the cow manure which reached an Ec average of 5.57 mS/cm over the period of the experiment. Chloride and bicarbonate levels were high and increased on all of the treatments at most sampling occasions of the trial, and sodium level was within the acceptable level.

Topographic controls on the variability of soil respiration in a humid subtropical forest

Knowledge of the spatial and temporal variabilities of soil respiration is important in estimating the soil carbon budget and in understanding how soils may respond to global changes. In areas with complex terrain, the topography can modify the hydrological conditions and other biophysical variables, which complicates the spatial and temporal heterogeneity of soil respiration. Herein, we investigated soil respiration along topographic transects with ridge, middle slope, lower slope and valley positions in a humid subtropical mountain forest in China to assess the driving factors of the variations in soil respiration. Our results showed that there were substantial temporal and spatial variations in soil respiration. The temporal variation of soil respiration could be well explained by the dynamics of soil temperature and moisture. Soil respiration rates also showed clear topographic pattern and decreased significantly from the ridge to valley soils, with the mean rates equaled 3.43 ± 0.13, 2.64 ± 0.30, 2.13 ± 0.26 and 1.88 ± 0.24 μmol m−2 s−1 at the ridge, middle slope, lower slope, and valley, respectively. Correlation analyses revealed that the spatial variation of soil respiration could be explained by multiple variables (e.g., soil temperature, basal area of the trees, thickness of the forest floor, root biomass and stock of soil dissolved carbon, soil C/N and soil bulk density). Results from partial least squares path modeling suggested that the topography modified the fine root distribution and the lateral losses of light and dissolved organic materials that created areas of high carbon sources for soil respiration at the ridge. The topographically regulated processes further resulted in a high soil C/N at the ridge that favored SOC decomposition. The higher respiration rate for the ridge soil and its higher sensitivity to soil temperature and moisture changes suggested that the ridge position was a potential hot spot for future environmental changes. Future studies and management practices regarding the soil carbon efflux in forest ecosystems with topographical variations should take into account the topographic effects.

Integrated influence of soil tillage, nitrogen–potassium fertiliser and mulching on pineapple (Ananas comosus (L.) Merr.) growth and yield

Pineapple is one of the most important fruit in the world and its production requires appropiate cultural practices. This work aimed to investigate the influences of soil tillage, nitrogen–potassium (N-K) fertiliser and mulching on pineapple growth and yield. The experimental design was a split-split plot with four replications. The main factor was soil tillage (at two levels: flat tillage and ridging), the subplot factor was N-K fertilisation (at five levels: 1.6 N and 1.6 K, 5.8 N and 6.6 K, 10 N and 11.6 K, 1.6 N and 11.6 K, and 10 N and 1.6 K, in g plant−1) and the sub-subplot factor was use of fresh pineapple residues (at three levels: surface mulching (at 10 t ha−1), 10 t ha−1 buried residues at 10 cm depth, and no mulching). Growth and yield parameters were recorded. A mixed ANOVA model was performed on ‘D’ leaf characteristics, biomass production and yield. The results suggested that soil ridging and burying of 1 kg m−2 of crop residues improved pineapple growth and yield. Nitrogen–potassium combinations 10 N and 11.6 K, 1.6 N and 11.6 K, and 5.8 N and 6.6 K (in g plant−1) resulted in better plant development and higher yield.

Development of a Combine Hoeing Machine for Flat and Ridged Soil

This study aims to develop a suitable hoeing machine for the crop planted at flat and the ridged soil with ridges reforming, and evaluate it by studying some effective factors such as blades shape, kinematic indices, crop planting methods and power requirements. The experiments were carried out in the Rice Mechanization Center at Meet El Deeba, Kafr El-Sheikh Governorate. The results indicated that using the developed machine using L-shaped blade increased the weeding efficiency by about 4%, plants damage about 0.8%, operating power requirement about 1.6% in comparison with C-shaped blade. In addition increasing the kinematic index increased the weeding efficiency and also plants damage percentage using L and C-shaped blades and crop planting methods.

Effects of ridge–furrow mulching on soil CO2 efflux in a maize field in the Chinese Loess Plateau

Ridge–furrow mulching system (RFMS) is widely used in arid and semi–arid areas, but its effect on soil respiration (Rs) and its components, including heterotrophic (Rh) and autotrophic respiration (Ra) are still poorly understood. In this study, CO2 flux from the soil of furrows and ridges was measured across different RFMS practices (i.e., three different ridge/furrow ratios) and conventional flat planting (CK). A trenching method was used to estimate the contribution of Rh to Rs. Compared with CK, RFMS significantly increased soil temperature of the ridge, promoted soil moisture of the furrow, and enhanced microbial diversity at the early crop growth stage, resulting in increased Rs and its components. The ridge soils exhibited much higher Rs (3.43 μmol m–2 s–1) than the furrow soils (2.98 μmol m–2 s–1) under all three RFMS practices. The contribution ratios of Rh to Rs across the different practices ranged from 50.4% to 59.6%. Soil temperature rather than soil moisture explained the seasonal variation of Rs and its components for both CK and RFMS. Nonetheless, high Rs and Rh values in RFMS did not induce a decline of soil organic carbon during the two–year experimental period. Improved root growth in RFMS practices may provide more exudates to the soil, thus offsetting soil carbon decomposition. Compared with CK, RFMS with ridge/furrow ratios of 40:70 cm, 55:55 cm, and 70:40 cm, significantly increased soil CO2 emissions by 10.6%, 19.6%, and 20.4%, respectively, while increasing maize yield by 26.1%, 36.4%, and 50.3%, respectively. Carbon emission efficiency (CEE) was significantly higher in RFMS than in CK in both years. This study suggests that, due to its high CEE, RFMS with a ridge/furrow ratio of 70:40 cm could be a highly promising strategy for sustaining crop productivity while minimizing environmental impacts.