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

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.

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.

Effects of Subsoiling on Soil Moisture Under No-Tillage for Two Years

In order to improve the water use efficiency under conservation tillage, the effects of subsoiling on soil moisture under notillage were studied. An experiment of 40 cm subsoiling in a field kept under no-tillage for 2 years was operated from 2005 to 2006. Based on the data of the soil moisture and crop yield, the physical basis of subsoiling for water conservation and yield increase was analyzed. The results showed that the soil water storage under subsoiling, from the soil surface to a depth of 100 cm was more than that under no-tillage for the growth season. In the 0-100 cm soil depth, the soil moisture in 50-100 cm depth under subsoiling was more compared with no-tillage, which increased when it＇s drought and decreased when it＇s rainy with the increase in soil depth. Compared with no-tillage, subsoiling could reduce the water consumption of oats in the 0-50 cm depth and increase the water consumption in the 50-100 cm depth. Also, subsoiling increased the yield by 18.29% and the water use efficiency by 16.8% in a two-year average. The effects of subsoiling on water conservation and yield increase were affected by precipitation, and a well-proportioned rainfall was better to increase yield and water use efficiency. Meanwhile, subsoiling decreased bulk density, which increased with the available precipitation. Subsoiling under no-tillage is the effective rotation tillage to contain more soil moisture and improve water use efficiency in ecotone of North China.

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 ifeld experiment to compare N2O emissions under monoculture and maize-legume intercropping systems. In 2010, ifve 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＆#177;0.12） to （1.17＆#177;0.11） kg ha-1 in 2010, while those ranged from （3.35＆#177;0.30） to （9.10＆#177;2.09） kg ha-1 in 2011. MA and MSC had no signiifcant effect on soil N2O production compared to that of M （P＆lt;0.05）. Cumulative N2O emissions from MP in 2010 were signiifcantly lower than those from M, but the result was the opposite in 2011 （P＆lt;0.05）. MS signiifcantly reduced soil N2O emissions by 25.55 and 48.84%in 2010 and 2011, respectively （P＆lt;0.05）. Soil N2O emissions were signiifcantly correlated with soil water content, soil temperature, nitriifcation potential, soil NH4＋, and soil NO3-content （R2=0.160-0.764, P＆lt;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＆lt;0.001）. These results indicate that MS had a coincident effect on soil N2O lfux and signiifcantly 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

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.

Harmony Coefficient and Regional Agricultural Systems

The regional agricultural system （RAS） can be divided into three subsystems： ecological, economic, and social. This article examines the use of the harmony coefficient （HC）, efficacy coefficient, rank of the harmony coefficient （RHC）, and its appraising index system within the RAS. The harmony coefficient function was developed using a variance coefficient and then applied to Ziyang District, Yiyang City in Hunan Province （ZYH）, China, as a test case. From 1995 to 2002, the HC of RAS increased from 0.2982 to 0.4826 and the RHC increased from 3 to 5, although the HC trend was an ＂n＂ type in general. This suggests that the HC was weakly maladjusted and the RAS was not harmonious. The HC of the ecological subsystem decreased from 0.3898 to 0.2850, and its RHC from 4 to 3, with the HC trend following the ＂n＂ type. For the economic subsystem, the HC value increased from 0.5767 to 0.7458 and the RHC from 6 to 8. However, the trend in HC for the economic subsystem was of the ＂U＂ type. The HC of the social subsystem increased slightly from 0.4948 to 0.4663, and the RHC did not change in value. From the HC trends, the HC curve of the economic subsystem is above the HC curve of ZYH and the HC curve of the ecological subsystem is below the HC curve of ZHY. Hence, the ZHY environment has been destroyed by economic development. Environment and social building should be regarded as important issues in the future and promoting RAS harmony development should be considered. The results of the theoretical analysis match fairly closely with reality, and suggest that the harmony theory is feasible in appraising RAS development phases.

中国种植业碳中和技术路径探讨与对策建议

碳达峰、碳中和(简称“双碳”)是中国推进高质量发展的重要战略之一,农业是“双碳”战略实施中不可忽视、不可或缺的重要领域。种植业是中国农业的主体,研究探索中国种植业碳中和实现路径具有重要意义。本文对相关关键问题进行理论认识梳理,分析国内外种植业固碳与温室气体排放相关研究进展,探讨了中国种植业实现碳中和的技术路径,并提出了提升中国种植业碳中和科技创新能力的建议。研究表明,目前关于种植业是“碳源”还是“碳汇”存在不同认识,急需建立标准化的农田碳核算方法体系。中国种植业实现碳中和需要基于系统观视角,从农用物质投入、农田生产过程管理、种植末端的废弃物处理等全过程统筹,从作物品种及种植模式、土壤水肥管理、农机耕作等全环节兼顾,通过农资合理减量、提升养分效率、物质循环利用、作物技术创新“四大”路径实现种植业减排增汇,形成系统性技术解决方案。因此,中国种植业要实现碳中和,急需强化种植业碳中和科技创新能力,重点需要强化农田生态系统碳中和科技创新、加强全国农业双碳平台基地建设、成立全国农业“双碳”研究联盟、谋划牵头农业碳中和国际科学研究合作项目。