Northeast Institute of Geography and Agroecology, Chinese Academy Of Sciences
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Evaluating ephemeral gully erosion impact on Zea mays L. yield and economics using AnnAGNPS
No full textEphemeral gully erosion causes serious water quality and economic problems in the Midwest United States. A critical barrier to soil conservation practice adoption is often the implementation cost, although it is recognized that erosion reduces farm income. Yet few, if any, understand the relationship between cost of conservation practice implementation and potential economic benefit gained from erosion control practices, especially as related to ephemeral gully erosion. The objectives of this research are to: (1) evaluate the soil loss and corresponding topsoil depth reduction due to annually ephemeral gully filling; and (2) estimate the economic loss associated with the crop production reduction attributed to topsoil thinning. Surface runoff and watershed sediment yield were flume measured at the approximately 1-ha drainage scale in Iowa. Sediment yield of the developing ephemeral gully was partitioned from measured total watershed sediment loss, by modeling ephemeral gully development with the Annualized Agricultural Non-Point Source Pollution model (AnnAGNPS), and subtracting this soil loss value from the flume measured watershed total. Topsoil thinning in the adjacent area used to fill the ephemeral gully was calculated based on the corresponding ephemeral gully sediment yield. The effect of A horizon thickness on corn yield obtained from published literature was used to calculate the corn (Zea mays L.) yield reduction due to topsoil thinning. Ephemeral gully erosion negatively impacts farm economics in the long term and implies that soil conservation measures should be carefully designed and well maintained. However, this evidence suggests that costs associated with establishment and use of structures such as grass waterways to minimize or eliminate ephemeral gully formation will not be recuperated in the short term through yield potential maintenance. (C) 2015 Elsevier B.V. All rights reserved
Experimental warming-driven soil drying reduced N2O emissions from fertilized crop rotations of winter wheat-soybean/fallow, 2009-2014
No full textNitrous oxide (N2O) emissions from agricultural soils play an important role in the global greenhouse gas budget. However, the response of N2O emissions from nitrogen fertilized agricultural soils to climate warming is not yet well understood. A field experiment with simulated warming (T) using infrared heaters and its control (C) combined with a nitrogen (N1) fertilization treatment (315 kg N ha(-1) y(-1)) and no nitrogen treatment (NO) was conducted over five years at an agricultural research station in the North China Plain in a winter wheat-soybean double cropping system. N2O fluxes were measured using static chambers about once every week during July 2009-June 2014. In the N1 treatment, warming decreased the soil moisture and N2O emissions in spring, autumn and winter and the annual cumulative emissions. Across all years, N2O fluxes were positively correlated with soil temperature and soil moisture. The effect of lower soil moisture on N2O fluxes exceeded that of higher temperature, leading to less N2O being released by the drier soils under warming. Nitrogen fertilizer increased N2O emissions without warming, but did not routinely increase N2O emissions under warming treatment. In the NO treatment, warming neither decreased soil water content nor N2O emissions. Temperature and nitrogen input had significant direct and antagonistic effects on cumulative N2O flux in the N1 treatment. The decrease in N2O emissions from N1 T was due to the significant decrease of soil water content, soil total nitrogen and organic matter, which consequently accelerated N cycle dynamics and advanced wheat growth. (C) 2015 Elsevier B.V. All rights reserved
Fate of N-15 fertilizer under different nitrogen split applications to plastic mulched maize in semiarid farmland
No full textA 2-year field microplot experiment was conducted to determine the effects of nitrogen (N) splits on grain yields and the fate of N-15-labelled fertilizer applied to plastic mulched maize (Zea mays L.). Three N split applications at the same rate of 225 kg N hm(-2) were performed. The N was applied at the day before sowing, the eight-leaf stage (V8), and the silking stage (R1) in the following ratios: 100 %-0-0 (N1), 40-60 %-0 (N2), and 40-30-30 % (N3). N-15-labelled urea (10.14 atom%) was used to trace the fate of each N application in the microplots. The results showed that grain yields increased by 8.3 and 10.7 % in the treatments N2 and N3, respectively, compared with the N1 treatment. Plant N uptake derived from fertilizer (Ndff, %) averaged 26.8-32.4 % compared with 67.6-73.2 % derived from soils (Ndfs, %). Split applications of N significantly increased the Ndff in plant. The residual N-15 in the 0-200 cm soil layer ranged from 48.3 to 51.3 % at maize harvest, approximately half of which remained in 0-20 cm soil layer. The N-15 recovery efficiency ((NRE)-N-15) was 37.5 and 39.1 % for treatments N2 and N3, respectively, and was significantly higher than that for N1 treatment (27.9 %). The potential N losses in the treatments N2 and N3 were 11.2 and 12.7 %, respectively, and were significantly lower than losses in treatment N1 (22.2 %). In conclusion, applying N with two splits could produce higher grain yields, higher NRE, and lower N losses in semiarid plastic mulched maize cropping system
Genetically engineered Pseudomonas putida X3 strain and its potential ability to bioremediate soil microcosms contaminated with methyl parathion and cadmium
No full textA multifunctional Pseudomonas putida X3 strain was successfully engineered by introducing methyl parathion (MP)-degrading gene and enhanced green fluorescent protein (EGFP) gene in P. putida X4 (CCTCC: 209319). In liquid cultures, the engineered X3 strain utilized MP as sole carbon source for growth and degraded 100 mg L-1 of MP within 24 h; however, this strain did not further metabolize p-nitrophenol (PNP), an intermediate metabolite of MP. No discrepancy in minimum inhibitory concentrations (MICs) to cadmium (Cd), copper (Cu), zinc (Zn), and cobalt (Co) was observed between the engineered X3 strain and its host strain. The inoculated X3 strain accelerated MP degradation in different polluted soil microcosms with 100 mg MP kg(-1) dry soil and/or 5 mg Cd kg(-1) dry soil; MP was completely eliminated within 40 h. However, the presence of Cd in the early stage of remediation slightly delayed MP degradation. The application of X3 strain in Cd-contaminated soil strongly affected the distribution of Cd fractions and immobilized Cd by reducing bioavailable Cd concentrations with lower soluble/exchangeable Cd and organic-bound Cd. The inoculated X3 strain also colonized and proliferated in various contaminated microcosms. Our results suggested that the engineered X3 strain is a potential bioremediation agent showing competitive advantage in complex contaminated environments
Impact of cultivation year, nitrogen fertilization rate and irrigation water quality on soil salinity and soil nitrogen in saline-sodic paddy fields in Northeast China
No full textSaline-sodic soils are widely distributed in the western Songnen Plain of Northeast China and planting rice has been found to be an effective and feasible approach for improving saline-sodic soil and increasing food production. Assessment of the effectiveness and sustainability of this method requires monitoring of the changes in soil salinity and nutrient content. The objective of the current study was to investigate the changes of soil salinity and nitrogen (N) contents over 1, 3, 6 and 9 years of cultivation, four application rates of N (N-0: no N, N-1: 100 kg N/ha, N-2: 200 kg N/ha and N-3: 300 kg N/ha) and two irrigation water types: ground water irrigation (GWI) and river water irrigation (RWI). Salinity and N contents of soil and water samples were analysed before planting and after harvest throughout the experiments. Soil pH and electrical conductivity (EC), especially in the surface layer of 0-40 cm depth, decreased with years of cultivation with both GWI and RWI, while soil inorganic N and total N contents increased. Moreover, with increasing N application rates, soil inorganic N and total N contents increased significantly in the 0-20 cm soil layer. Increasing N application had little effect on soil pH and EC. Reclaiming and planting rice promoted desalination of the surface and formation of a fertile tillage layer in saline-sodic paddy fields. In terms of irrigation and drainage in saline-sodic paddy fields, both soil salinity and N contents increased. Soil total salinity increased annually by 34 and 12.8 kg/ha, and inorganic N contents increased annually by 9 and 13.5 kg/ha with GWI and RWI, respectively. Therefore, comprehensive agricultural practices should be adopted for improving and cropping rice in saline-sodic paddy fields
Microwave Unmixing With Video Segmentation for Inferring Broadleaf and Needleleaf Brightness Temperatures and Abundances From Mixed Forest Observations
No full textPassive microwave sensors have better capability of penetrating forest layers to obtain more information from forest canopy and ground surface. For forest management, it is useful to study passive microwave signals from forests. Passive microwave sensors can detect signals from needleleaf, broadleaf, and mixed forests. The observed brightness temperature of a mixed forest can be approximated by a linear combination of the needleleaf and broadleaf brightness temperatures weighted by their respective abundances. For a mixed forest observed by an N-band microwave radiometer with horizontal and vertical polarizations, there are 2 N observed brightness temperatures. It is desirable to infer 4 N + 2 unknowns: 2 N broadleaf brightness temperatures, 2 N needleleaf brightness temperatures, 1 broadleaf abundance, and 1 needleleaf abundance. This is a challenging underdetermined problem. In this paper, we devise a novel method that combines microwave unmixing with video segmentation for inferring broadleaf and needleleaf brightness temperatures and abundances from mixed forests. We propose an improved Otsu method for video segmentation to infer broadleaf and needleleaf abundances. The brightness temperatures of needleleaf and broadleaf trees can then be solved by the nonnegative least squares solution. For our mixed forest unmixing problem, it turns out that the ordinary least squares solution yields the desired positive brightness temperatures. The experimental results demonstrate that the proposed method is able to unmix broadleaf and needleleaf brightness temperatures and abundances well. The absolute differences between the reconstructed and observed brightness temperatures of the mixed forest are well within 1 K
Nitrogen and Phoshporus Removal by Five Ornamental and Wetland Plants from Upstream of Hunhe River, China
No full textPhytoremediation is a promising technique to remove nitrogen (N) and phosphorus (P) from wastewater by plants, and it is useful to control eutrophication and restore the water ecosystem. In the present study, five ornamental and wetland plants, Lythrum salicaria, Alisma orientale, Acorus calamus, Monochoria korsakowii and Sagittaria sagittifolia, are chosen to study the effects of N and P on plant growth and chlorophyll contents, and evaluate the removal ability of N and P by the five aquatic plants. It was shown that the changes of chlorophyll contents in A. calamus and M. korsakowii were accordance with their better growth. The results indicated that the good tolerance of the two plants to N and P might result from the effective mechanisms including the capacity to maintain good growth and photosynthetic pigment composition, which would be useful for the plant's utility in phytoremediating water contaminated by N and P. A. calamus had the highest relative growth rate (RGR), and had the best removal efficiency of TN (95.3%) and TP (95.4%), which indicated that the plant could be considered as the most promising one for phytoremediating N and P contamination in the wastewater. The study results would provide a reference for the construction of wetland technology
Optimum harvest maturity for Leymus chinensis seed
No full textTimely harvest is critical to achieve maximum seed viability and vigour in agricultural production. However, little information exists concerning how to reap the best quality seeds of Leymus chinensis, which is the dominant and most promising grass species in the Songnen Grassland of Northern China. The objective of this study was to investigate and evaluate possible quality indices of the seeds at different days after peak anthesis. Seed quality at different development stages was assessed by the colours of the seed and lemmas, seed weight, moisture content, electrical conductivity of seed leachate and germination indices. Two consecutive years of experimental results showed that the maximum seed quality was recorded at 39 days after peak anthesis. At this date, the colours of the seed and lemmas reached heavy brown and yellow, respectively. The seed weight was highest and the moisture content and the electrical conductivity of seed leachate were lowest. In addition, the seed also reached its maximum germination percentage and energy at this stage, determined using a standard germination test (SGT) and accelerated ageing test (AAT). Thus, Leymus chinensis can be harvested at 39 days after peak anthesis based on the changes in parameters. Colour identification can be used as an additional indicator to provide a more rapid and reliable measure of optimum seed maturity; approximately 10 days after the colour of the lemmas reached yellow and the colour of the seed reached heavy brown, the seed of this species was suitable for harvest
Quantification winter wheat LAI with HJ-1CCD image features over multiple growing seasons
No full textRemote sensing images are widely used to map leaf area index (LAI) continuously over landscape. The objective of this study is to explore the ideal image features from Chinese HJ-1 A/B CCD images for estimating winter wheat LAI in Beijing. Image features were extracted from such images over four seasons of winter wheat growth, including five vegetation indices (VIs), principal components (PC), tasseled cap transformations (TCT) and texture parameters. The LAI was significantly correlated with the near-infrared reflectance band, five VIs [normalized difference vegetation index, enhanced vegetation index (EVI), modified nonlinear vegetation index (MNLI), optimization of soil-adjusted vegetation index, and ratio vegetation index], the first principal component (PC1) and the second TCT component (TCT2). However, these image features cannot significantly improve the estimation accuracy of winter wheat LAI in conjunction with eight texture measures. To determine the few ideal features with the best estimation accuracy, partial least squares regression (PLSR) and variable importance in projection (VIP) were applied to predict LAI values. Four remote sensing features (TCT2, PC1, MNLI and EVI) were chosen based on VIP values. The result of leave-one-out cross-validation demonstrated that the PLSR model based on these four features produced better result than the ten features' model, throughout the whole growing season. The results of this study suggest that selecting a few ideal image features is sufficient for LAI estimation. (C) 2015 Elsevier B.V. All rights reserved
Tonic Immobility Behavior Used by Lobella sokamensis to Adapt Water-saturated Environment in Marshes
No full textCollembola is well known as one of the most important soil meso-faunas of terrestrial ecosystem. As terrestrial arthropods, some water-dependent Collembola live in or near water environment. However, hydrodynamic analysis of water-walking showed that Collembola individuals retain smooth end of claw which are barely high efficient for water walking. The high abundance of Collembola habiting in the wetlands implies an important water-adaptive way of water moving that exists in these animals. This study chose Lobella sokamensis as sample; it is uniquely distributed in and near standing water in the marshes in Northeast China. In order to test the function of water to habitat selecting, free choice behavior experiment was set at a water gradient arena and the effect of the plants in the marshes was analyzed through double choice test. The numbers of the animals stayed at dry, mediated, wet areas were recorded after 0.5 hour, 11 hours, 23 hours, and 32 hours in free choice behavior and analyzed the data with SPSS software. Analogue method and data analysis was applied at double choice test. In order to describe the movement feature of Lobella sokamensis on the water, the activity on the water surface was observed. The results showed that the species had water-repellent and moss-attractive behavior. Tonic immobility gesture was observed when the animal floating on water surface and it was quite efficient for escaping from water when water level was fluctuating. The water flow increased Lobella sokamensis’s transferring in the wetlands. The results illustrated that the moss in the wetlands was vital for distribution of Lobella sokamensis, but tonic immobility was basic for population diffusing for this inactive Collembola. The importance of close connection of moss and water was indicated in the paper, which should be concerned during Collembola biodiversity preserving in the Sanjiang Plain. This is the first demonstration of immobility behavior for water adaptation in Collembola from the wetlands