Yuanquan Chen

Recharge and groundwater use in the North China Plain for six irrigated crops for an eleven year period.

Water tables are dropping by approximately one meter annually throughout the North China Plain mainly due to water withdrawals for irrigating winter wheat year after year. In order to examine whether the drawdown can be reduced we calculate the net water use for an 11 year field experiment from 2003 to 2013 where six irrigated crops (winter wheat, summer maize, cotton, peanuts, sweet potato, ryegrass) were grown in different crop rotations in the North China Plain. As part of this experiment moisture contents were measured each at 20 cm intervals in the top 1.8 m. Recharge and net water use were calculated based on these moisture measurement. Results showed that winter wheat and ryegrass had the least recharge with an average of 27 mm/year and 39 mm/year, respectively; cotton had the most recharge with an average of 211 mm/year) followed by peanuts with 118 mm/year, sweet potato with 76 mm/year, and summer maize with 44 mm/year. Recharge depended on the amount of irrigation water pumped from the aquifer and was therefore a poor indicator of future groundwater decline. Instead net water use (recharge minus irrigation) was found to be a good indicator for the decline of the water table. The smallest amount of net (ground water) used was cotton with an average of 14 mm/year, followed by peanut with 32 mm/year, summer maize with 71 mm/year, sweet potato with 74 mm/year. Winter wheat and ryegrass had the greatest net water use with the average of 198 mm/year and 111 mm/year, respectively. Our calculations showed that any single crop would use less water than the prevalent winter wheat summer maize rotation. This growing one crop instead of two will reduce the decline of groundwater and in some rain rich years increase the ground water level, but will result in less income for the farmers.

Estimation of net greenhouse gas balance using crop- and soil-based approaches: Two case studies

The net greenhouse gas balance (NGHGB), estimated by combining direct and indirect greenhouse gas (GHG) emissions, can reveal whether an agricultural system is a sink or source of GHGs. Currently, two types of methods, referred to here as crop-based and soil-based approaches, are widely used to estimate the NGHGB of agricultural systems on annual and seasonal crop timescales. However, the two approaches may produce contradictory results, and few studies have tested which approach is more reliable. In this study, we examined the two approaches using experimental data from an intercropping trial with straw removal and a tillage trial with straw return. The results of the two approaches provided different views of the two trials. In the intercropping trial, NGHGB estimated by the crop-based approach indicated that monocultured maize (M) was a source of GHGs (-1315 kg CO₂(-eq)ha(-1)), whereas maize-soybean intercropping (MS) was a sink (107 kg CO₂(-eq)ha(-1)). When estimated by the soil-based approach, both cropping systems were sources (-3410 for M and -2638 kg CO₂(-eq)ha(-1) for MS). In the tillage trial, mouldboard ploughing (MP) and rotary tillage (RT) mitigated GHG emissions by 22,451 and 21,500 kg CO₂(-eq)ha(-1), respectively, as estimated by the crop-based approach. However, by the soil-based approach, both tillage methods were sources of GHGs: -3533 for MP and -2241 kg CO₂(-eq)ha(-1) for RT. The crop-based approach calculates a GHG sink on the basis of the returned crop biomass (and other organic matter input) and estimates considerably more GHG mitigation potential than that calculated from the variations in soil organic carbon storage by the soil-based approach. These results indicate that the crop-based approach estimates higher GHG mitigation benefits compared to the soil-based approach and may overestimate the potential of GHG mitigation in agricultural systems.

Review of Current Status and Research Approaches to Nitrogen Pollution in Farmlands

In this paper, the history, current status, and research approaches to nitrogen pollution were reviewed using systems analysis and deductions. The seriousness of N pollution world-wide was highlighted and recommendations were made to address the situation. A new hypothesis based on phytoremediation, which means the use of plants to directly or indirectly degrade or remove contaminats from soil and water, was proposed.

Subsoiling and Ridge Tillage Alleviate the High Temperature Stress in Spring Maize in the North China Plain

Abstract High temperature stress (HTS) on spring maize ( Zea mays L.) during the filling stage is the key factor that limits the yield increase in the North China Plain (NCP). Subsoiling (SS) and ridge tillage (R) were introduced to enhance the ability of spring maize to resist HTS during the filling stage. The field experiments were conducted during the 2011 and 2012 maize growing seasons at Wuqiao County, Hebei Province, China. Compared with rotary tillage (RT), the net photosynthetic rate, stomatal conductance, transpiration rate, and chlorophyll relative content (SPAD) of maize leaves was increased by 40.0, 42.6, 12.8, and 29.7% under SS, and increased by 20.4, 20.0, 5.4, and 14.2% under R, repectively. However, the treatments reduce the intercellular CO 2 concentration under HTS. The SS and R treatments increased the relative water content (RWC) by 11.9 and 6.2%, and the water use efficiency (WUE) by 24.3 and 14.3%, respectively, compared with RT. The SS treatment increased the root length density and soil moisture in the 0-80 cm soil profile, whereas the R treatment increased the root length density and soil moisture in the 0-40 cm soil profile compared with the RT treatment. Compared with 2011, the number of days with temperatures ⩾33°C was more 2 d and the mean day temperature was higher 0.9°C than that in 2012, whereas the plant yield decreased by 2.5, 8.5 and 10.9%, the net photosynthetic rate reduced by 7.5, 10.5 and 18.0%, the RWC reduced by 3.9, 5.6 and 6.2%, and the WUE at leaf level reduced by 1.8, 5.2 and 13.1% in the SS, R and RT treatments, respectively. Both the root length density and the soil moisture also decreased at different levels. The yield, photosynthetic rate, plant water status, root length density, and soil moisture under the SS and R treatments declined less than that under the RT treatment. The results indicated that SS and R can enhance the HTS resistance of spring maize during the filling stage, and led to higher yield by directly improving soil moisture and root growth and indirectly improving plant water status, photosynthesis and grain filling. The study can provide a theoretical basis for improving yield of maize by adjusting soil tillage in the NCP.

Nitrate Leaching from Maize Intercropping Systems with N Fertilizer Over-Dose

Abstract A 2-yr field experiment was conducted on a calcareous alluvial soil with four summer maize intercropping systems at Shangzhuang Experiment Station (116.3°E, 39.9°N) in the North China Plain. The objective was to determine nitrate leaching from intercropping systems involving maize (Zea mays L.): sole maize (CK), maize + soybean (CST), maize + groundnut (CGT), maize + ryegrass (CHM), and maize + alfalfa (CMX). Intercropping greatly reduced nitrate accumulation in the 100-200 cm soil layers compared with maize monoculture. Nitrate accumulation under intercropping systems decreased significantly at the 140-200 cm soil depth; the accumulation varied in the order CK>CST>CMX>CHM>CGT. However, compared to the CK treatment, nitrate leaching losses during the maize growing period were reduced by 20.9-174.8 (CGT), 35.2-130.8 (CHM), 60.4-122.0 (CMX), and 30.6-82.4 kg ha −1 (CST). The results also suggested that intercropping is an effective way to reduce nitrogen leaching in fields with N fertilizer over-dose.

Soil Nitrous Oxide Emissions Under Maize-Legume Intercropping System in the North China Plain

Many studies have focused on various agricultural management measures to reduce agricultural nitrous oxide (N2O) emission. However, few studies have investigated soil N2O emissions in intercropping systems in the North China Plain. Thus, we conducted a field experiment to compare N2O emissions under monoculture and maize-legume intercropping systems. In 2010, five treatments, including monocultured maize (M), maize-peanut (MP), maize-alfalfa (MA), maize-soybean (MS), and maize-sweet clover (MSC) intercropping were designed to investigate this issue using the static chamber technique. In 2011, M, MP, and MS remained, and monocultured peanuts (P) and soybean (S) were added to the trial. The results showed that total production of N2O from different treatments ranged from (0.87±0.12) to (1.17±0.11) kg ha−1 in 2010, while those ranged from (3.35±0.30) to (9.10±2.09) kg ha−1 in 2011. MA and MSC had no significant effect on soil N2O production compared to that of M (P<0.05). Cumulative N2O emissions from MP in 2010 were significantly lower than those from M, but the result was the opposite in 2011 (P<0.05). MS significantly reduced soil N2O emissions by 25.55 and 48.84% in 2010 and 2011, respectively (P<0.05). Soil N2O emissions were significantly correlated with soil water content, soil temperature, nitrification potential, soil NH4+, and soil NO3− content (R2=0.160-0.764, P<0.01). A stepwise linear regression analysis indicated that soil N2O release was mainly controlled by the interaction between soil moisture and soil NO3− content (R2=0.828, P<0.001). These results indicate that MS had a coincident effect on soil N2O flux and significantly reduced soil N2O production compared to that of M over two growing seasons.

Aggregate stability and associated C and N in a silty loam soil as affected by organic material inputs

Abstract To make recycling utilization of organic materials produced in various agricultural systems, five kinds of organic materials were applied in a field test, including crop straw (CS), biogas residue (BR), mushroom residue (MR), wine residue (WR), pig manure (PM), with a mineral fertilizer (CF) and a no-fertilizer (CK) treatment as a control. Our objectives were: i) to quantify the effects of organic materials on soil C and N accumulation; ii) to evaluate the effects of organic materials on soil aggregate stability, along with the total organic carbon (TOC), and N in different aggregate fractions; and iii) to assess the relationships among the organic material components, soil C and N, and C, N in aggregate fractions. The trial was conducted in Wuqiao County, Hebei Province, China. The organic materials were incorporated at an equal rate of C, and combined with a mineral fertilizer in amounts of 150 kg N ha −1 , 26 kg P ha −1 and 124 kg K ha −1 respectively during each crop season of a wheat-maize rotation system. The inputted C quantity of each organic material treatment was equivalent to the total amount of C contained in the crop straw harvested in CS treatement in the previous season. TOC, N, water-stable aggregates, and aggregate-associated TOC and N were investigated. The results showed that organic material incorporation increased soil aggregation and stabilization. On average, the soil macroaggregate proportion increased by 14%, the microaggregate proportion increased by 3%, and mean-weight diameter (MWD) increased by 20%. TOC content followed the order of PM>WR>MR>BR>CS>CK>CF; N content followed the order WR>PM>MR>BR>CS>CF>CK. No significant correlation was found between TOC, N, and the quality of organic material. Soil silt and clay particles contained the largest part of TOC, whereas the small macroaggregate fraction was the most sensitive to organic materials. Our results indicate that PM and WR exerted better effects on soil C and N accumulation, followed by MR and BR, suggesting that organic materials from ex situ farmland could promote soil quality more as compared to straw returned in situ.

Xanthium Suppression Under Maize||Sunflower Intercropping System

Abstract Weed control is one of the major constraint factors in crop production around the world. Field experiments were conducted during 2008-2009 under intercropping systems involving alfalfa ( Medicago sativa L.), sweet potato ( Ipomoea batatas [L.] Lam.), peanut ( Arachis hypogaea L.), and sunflower ( Helianthus annuus L.) in maize ( Zea mays L.) without any weeds control methods taken. The results demonstrate that maize||sunflower is most effective on weed suppression and that it also has a more competitively inhibitory effect on Xanthium compared with the other patterns by evaluating the Xanthium density and dry weight under different intercropping systems with maize. Maize||peanut, maize||alfalfa and maize||sweet potato intercrops have no apparent inhibitory effect on weeds. To further investigate the effect of maize||sunflower on weed control, indoor pot experiments were conducted by determining the effect of extractions on germination rate (GR), root vigor, MDA (malondialdehyde), SOD (superoxide dismutase) and POD (peroxidase) content of Xanthium . The results better prove that maize||sunflower extractions have more significant inhibitory effect on GR and young root vigor of Xanthium than maize monocrop extractions.

Myostatin gene targeting in cultured China Han ovine myoblast cells

Myostatin (MSTN), a member of the transforming growth factor-β superfamily, has been shown to be a negative regulator of myogenesis. Natural mutation in beef cattle causes double-muscling phenotypes. We report an investigation designed to knockout the MSTN gene by gene targeting in ovine myoblast cells. Two promoter-trap targeting vectors MSTN-green fluorescent protein (GFP) and MSTN-neo were constructed and used to transfect foetal and neonatal ovine primary myoblast cells. Both GFP-expressing cells and drug-resistant cells were obtained. Targeted cells expressing GFP were confirmed by polymerase chain reaction (PCR) assay and drug-resistant cells were characterised by PCR and Southern blot after growing into cell clones.

Research progress of evaluation system for China circular agriculture development: Research progress of evaluation system for China circular agriculture development

Research and practices on circular agriculture(CA) has been hotspots of Chinese agriculture development in recent years.CA plays a significant role in resource using,energy saving,emission reduction,enterprise and industry development,and farmer income improvement in China.How to build a suitable evaluation system is one of the top issues on the CA research and development.In this paper,the general progresses of CA researches were discussed,and the evaluating content,indicators and methods were summarized as well.Generally,the evaluation for CA was classified as two types.The first was macro-evaluation focusing on the national or regional scale,whose indexes were constructed base on the social and economic development,resource reduces,resource recycle and safety of resource and environment dimensions.The goal of this kind of evaluation was to determined the social,economic and ecological effects of CA development.Another kind was micro-evaluation focusing on the industrial park,enterprise,or local farm system scale,whose goal was assessment of the features of materials cycling and energy flow in CA systems,and the environment impacts as well.Many methods were introduced in this kind evaluation including system dynamic,emergy,life cycle assessment,etc.At the same time,there existed marked difference in evaluating content,indicators and methods for the micro-evaluation.Furthermore,the suitable evaluation index for different scales(national,regional,enterprise,detailed pattern or technology,etc.) were expected to further study,which should be according with the 4R rule(recycle,reuse,reduce and regulate) of CA.