Rongjiang Yao

The Effects of Farmyard Manure and Mulch on Soil Physical Properties in a Reclaimed Coastal Tidal Flat Salt-Affected Soil

Careful soil management is important for the soil quality and productivity improvement of the reclaimed coastal tidal flat saline land in northern Jiangsu Province, China. Farmyard manure (FYM) and mulch applications, which affect soil characteristics and plant significantly, are regard as an effective pattern of saline land improvement. As a conventional management in the study region, FYM and mulch are used for the amendment of the new reclaimed tidal flat regularly, but little is known about their effects on soil physical properties functioning. A study was conducted on a typical coastal tidal flat saline land, which was reclaimed in 2005, to evaluate the effects of FYM, polyethylene film mulch (PM), straw mulch (SM), FYM combined with PM (FYM+PM), FYM combined with SM (FYM+SM), on soil hydraulic properties and soil mechanical impedance. CK represented conventional cultivation in study area without FYM and mulch application and served as a control. The experiment, laid out in a randomized complete block design with three replications, was studied in Huanghaiyuan Farm, which specialized in the agricultural utilization for coastal tidal flat. Result showed that capillary water holding capacity (CHC), saturated water content (SWC), saturated hydraulic conductivity (Ks) and bulk density (BD), cone index (CI) were affected significantly by the FYM and mulch application, especially in the 0-10 cm soil layer. FYM and mulch management increased CHC, SWC and Ks over all soil depth in the order of FYM+SM>FYM+PM>FYM>SM>PM>CK. With the contrary sequence, BD and CI decreased significantly; however, FYM and mulch application affected BD and CI only in the upper soil layers. CHC, SWC and Ks decreased significantly with the increasing of soil depth, BD and CI, and a significant liner equation was found between CHC, SWC, Ks and BD, CI. With the highest CHC (38.15%), SWC (39.55%), Ks (6.00 mm h−1) and the lowest BD (1.26 g cm−3) and CI (2.71 MPa), the combined management of FYM and SM was recommend to be an effective method for the melioration of reclaimed coastal tidal flat saline soil.

Digital Mapping of Soil Salinity and Crop Yield across a Coastal Agricultural Landscape Using Repeated Electromagnetic Induction (EMI) Surveys

Reliable and real-time information on soil and crop properties is important for the development of management practices in accordance with the requirements of a specific soil and crop within individual field units. This is particularly the case in salt-affected agricultural landscape where managing the spatial variability of soil salinity is essential to minimize salinization and maximize crop output. The primary objectives were to use linear mixed-effects model for soil salinity and crop yield calibration with horizontal and vertical electromagnetic induction (EMI) measurements as ancillary data, to characterize the spatial distribution of soil salinity and crop yield and to verify the accuracy of spatial estimation. Horizontal and vertical EMI (type EM38) measurements at 252 locations were made during each survey, and root zone soil samples and crop samples at 64 sampling sites were collected. This work was periodically conducted on eight dates from June 2012 to May 2013 in a coastal salt-affected mud farmland. Multiple linear regression (MLR) and restricted maximum likelihood (REML) were applied to calibrate root zone soil salinity (ECe) and crop annual output (CAO) using ancillary data, and spatial distribution of soil ECe and CAO was generated using digital soil mapping (DSM) and the precision of spatial estimation was examined using the collected meteorological and groundwater data. Results indicated that a reduced model with EMh as a predictor was satisfactory for root zone ECe calibration, whereas a full model with both EMh and EMv as predictors met the requirement of CAO calibration. The obtained distribution maps of ECe showed consistency with those of EMI measurements at the corresponding time, and the spatial distribution of CAO generated from ancillary data showed agreement with that derived from raw crop data. Statistics of jackknifing procedure confirmed that the spatial estimation of ECe and CAO exhibited reliability and high accuracy. A general increasing trend of ECe was observed and moderately saline and very saline soils were predominant during the survey period. The temporal dynamics of root zone ECe coincided with those of daily rainfall, water table and groundwater data. Long-range EMI surveys and data collection are needed to capture the spatial and temporal variability of soil and crop parameters. Such results allowed us to conclude that, cost-effective and efficient EMI surveys, as one part of multi-source data for DSM, could be successfully used to characterize the spatial variability of soil salinity, to monitor the spatial and temporal dynamics of soil salinity, and to spatially estimate potential crop yield.

Soil quality in east coastal region of China as related to different land use types

PurposeThe impacts of different land use practices on soil quality were assessed by measuring soil attributes and using factor analysis in coastal tidal lands. The study provided relevant references for coastal exploitation, land management and related researches in other countries and regions.Materials and methodsMeasured soil attributes include physical indicators [bulk density (ρb), total porosity (ƒt) and water-holding capacity (WHC)], chemical indicators [pH, electrical conductivity (EC), total nitrogen (TN), soil organic matter (SOM), available N, available P and available K] and biological indicators (urease activity, catalase activity and phosphatase activity), and 60 soil samples were collected within five land use types [(1) intertidal soils, (2) reclaimed tidal flat soils, (3) farmland soils, (4) suburban vegetable soils, (5) industrial area soils) in Jianggang village of Dongtai county, Jiangsu province of China.Results and discussionThe results from the investigation indicated that selected soil properties reduced to three factors for 0–20-cm soil depth; “Soil fertility status” (factor 1), “Soil physical status” (factor 2) and “Soil salinity status” (factor 3). For the first factor, the measured soil attributes with higher loadings were TN and SOM, which represented soil fertility feature, and for the second and third factors, the measured soil attributes with higher loadings were ρb and available K as well as EC, which reflected soil physical properties and soil salinity feature, respectively.ConclusionsChanges in different land use types due to plants (corn, wheat and green vegetable) and application of fertilizers were characterized by promoted soil quality, including improvements in chemical properties (increasing SOM concentration, TN and nutrient available to plants; decreasing EC), improvements in soil physical properties (decreasing ρb; increasing ƒt and WHC) and enhancements in soil enzyme activities. Judging from the soil quality indices, the soil quality was affected by different land use practices and decreased in sequence of suburban vegetable soils, farmland soils, industrial area soils, reclaimed tidal flat soils and intertidal soils in the study area.

Fertilization Affects Biomass Production of Suaeda salsa and Soil Organic Carbon Pool in East Coastal Region of China

Abstract Land use practice significantly affects soil properties. Soil is a major sink for atmospheric carbon, and soil organic carbon (SOC) is considered as an essential indicator of soil quality. The objective of this study was to assess the effects of N and P applied to Suaeda salsa on biomass production, SOC concentration, labile organic carbon (LOC) concentration, SOC pool and carbon management index (CMI) as well as the effect of the land use practice on soil quality of coastal tidal lands in east coastal region of China. The study provided relevant references for coastal exploitation, tidal land management and related study in other countries and regions. The field experiment was laid out in a randomized complete block design, consisting of four N-fertilization rates (0 (N0), 60 (N1), 120 (N2) and 180 kg ha−1 (N3)), three P-fertilization rates (0 (P0), 70 (P1) and 105 kg ha−1 (P2)) and bare land without vegetation. N and P applied to S. salsa on coastal tidal lands significantly affected biomass production (above-ground biomass and roots), bulk density (ρb), available N and P, SOC, LOC, SOC pool and CMI. Using statistical analysis, significantly interactions in N and P were observed for biomass production and the dominant factor for S. salsa production was N in continuous 2-yr experiments. There were no significant interactions between N and P for SOC concentration, LOC concentration and SOC pool. However, significant interaction was obtained for CMI at the 0-20 cm depth and N played a dominant role in the variation of CMI. There were significant improvements for soil measured attributes and parameters, which suggested that increasing the rates of N and P significantly decreased ρb at the 0–20 cm depth and increased available N and P, SOC, LOC, SOC pool as well as CMI at both the 0–20 and 20–40 cm depth, respectively. By correlation analysis, there were significantly positive correlations between biomass (above-ground biomass and roots) and SOC as well as LOC in 2010 and 2011 across all soil depth, respectively. The treatment with N at 180 kg ha−1 and P at 105 kg ha−1 was superior to the other treatments. The results from the 2-yr continuous experiments indicated that, in short-term, there were a few accumulation of SOC and LOC concentrations by means of N and P application to S. salsa, whereas in the long run, S. salsa with N and P application was recommended for coastal tidal lands because of its great potential of carbon sequestration, improvements of soil nutrition status and promotion of soil quality.

Determining soil salinity and plant biomass response for a farmed coastal cropland using the electromagnetic induction method

An interval of 16m in EM survey transect meet the need of spatial prediction.Salt accumulation occurs in shallow groundwater area and lower-lying regions.Plant biomass is better explained by measured ECe than by estimated ECe.Relationship between ECe and crop biomass helps to derive site specific yield goals. Apparent electrical conductivity (ECa) measured by electromagnetic induction (EM) instruments has been successfully used as an ancillary variable to estimate soil salinity from field to watershed scales. It is particularly useful in the case of coastal farming area where reliable estimates of soil salinity aid farmers and researchers in understanding the development of salinization and establishing appropriate management practices. The objectives of this research were to estimate soil salinity (ECe) using intensive EM survey data and prediction equations relating soil salinity to ECa, to determine the optimal data interval in EM survey and to validate the prediction reliability using plant biomass response to soil salinity. This study was conducted in a typical coastal rain-fed farmland in north Jiangsu Province, China. The results indicated that apparent electrical conductivity showed significant correlation with ECe and EM readings from the horizontal coil orientation can be used as the sole predictor in a linear mixed model. Field EM survey data exhibited directional trend resulting from the impact of anthropogenic activities on soil salinity. An optimal sampling interval of 16m in the survey transect essentially meets the need of spatial prediction when field EM survey is performed. Soil salinity increased with depth and higher soil salinity mainly occurs in areas where rice was previously planted, particularly in lower-lying regions and areas adjacent to the aquaculture plant. Plant biomass is negatively related to both, measured and estimated soil salinity. The relation to measured soil salinity was closer than to estimated soil salinity. Boundary line analysis shows that root zone salinity (ECe) causes a 4.4% and 6.4% plant biomass reduction per dS/m for rice and cotton, respectively. Such results allowed us to conclude that a larger data interval of EM survey than the present could produce satisfactory estimation accuracy of field soil salinity, and the relationship between soil salinity (or ECa data) and plant biomass could help to derive site specific yield goals and management practices in the farmed coastal cropland.

Effects of Rice-Wheat Rotation and Afforestation on Microbial Biomass Carbon in Coastal Salt-Affected Soils of Eastern China

Abstract Rice-wheat rotation and poplar afforestation are two typical land use types in the coastal reclaimed flatlands of eastern China. This study investigated two rice-wheat rotation lands (one reclaimed from 1995 to 2004 and cultivated since 2005, RW1, and the other reclaimed from 1975 to 1995 and cultivated since 1996, RW2) and a poplar woodland (reclaimed from 1995 to 2004 and planted in 2004, PW1) to determine the effects of land use types and years of cultivation on soil microbial biomass and mineralizable carbon (C) in this coastal salt-affected region. The results showed that the soil in PW1 remained highly salinized, whereas desalinization was observed in RW1. The total organic C (TOC) in the top soil of PW1 and RW1 did not show significant differences, whereas at a soil depth of 20–30 cm, the TOC of RW1 was approximately 40%–67% higher than that of PW1. The TOC of 0–30-cm soil in RW2 was approximately 37% higher than that in RW1. Microbial biomass C (MBC) and mineralizable C (MNC) exhibited the trend of RW2 > RW1 > PW1. Sufficient nutrition with more abundant C substrates resulted in higher MBC and MNC, and soil respiration rates were negatively correlated with C/N in RW1 and RW2. Nutrient deficiency and high salinity played key roles in limiting MBC in PW1. These suggested that rice-wheat rotation was more beneficial than poplar afforestation for C accumulation and microbial biomass growth in the coastal salt-affected soils.