Soil carbon sequestration under long-term rice-based cropping systems of purple soil in Southwest China

Carbon sequestration in agricultural soils is a complex process controlled by farming practices, climate and some other environment factors. Since purple soils are unique in China and used as the main cropland in Sichuan Basin of China, it is of great importance to study and understand the impacts of different fertilizer amendments on soil organic carbon（SOC） changes with time. A research was carried out to investigate the relationship between soil carbon sequestration and organic carbon input as affected by different fertilizer treatments at two long-term rice-based cropping system experiments set up in early 1980 s. Each experiment consisted of six identical treatments, including（1） no fertilizer（CK）,（2） nitrogen and phosphorus fertilizers（NP）,（3） nitrogen, phosphorus and potassium fertilizers（NPK）,（4） fresh pig manure（M）,（5） nitrogen and phosphorus fertilizers plus manure（MNP）, and（6） nitrogen, phosphorus and potassium fertilizers plus manure（MNPK）. The results showed that annual harvestable carbon biomass was the highest in the treatment of MNPK, followed by MNP and NPK, then M and NP, and the lowest in CK. Most of fertilizer treatments resulted in a significant gain in SOC ranging from 6.48 to 2 9.13% compared with the CK, and raised soil carbon sequestration rate to 0.10–0.53 t ha–1 yr-1. Especially, addition of manure on the basis of mineral fertilizers was very conducive to SOC maintenance in this soil. SOC content and soil carbon sequestration rate under balanced fertilizer treatments（NPK and MNPK） in the calcareous purple soil（Suining） were higher than that in the acid purple soil（Leshan）. But carbon conversion rate at Leshan was 11.00%, almost 1.5 times of that（7.80%） at Suining. Significant linear correlations between soil carbon sequestration and carbon input were observed at both sites, signifying that the purple soil was not carbon-saturated and still had considerable potential to se questrate more carbon.

Effect of Rice-Based Cropping System on Organic Matter Status in Soils

A long-term simulation experiment was carried out to study the effect of rice-based cropping system,green manure and ground-water level on soil organic matter. Soil organic matter content increased when upland soil was puddled and cropped under submerged conditions. Among all treatments, soil organic matter contents in the treatments of rice-rice-flooded fallow in winter (WF) were the highest, those in the treatments of rice-rice-astragalus (WG) came the second, and those in the treatments of rice-rice-rape (WR)were the lowest. At the same rate of green manure application, the degrees of organo-mineral complexing in soils of treatments WG and WR were higher than those of treatment WF. After 9-year rice cultivation, the state of combination of humus in heavy fraction varied with treatments. The relative content of loosely bonded humus decreased in the order of WR > WG > WF, and it correlated significantly with Se availability.

信息技术:走向农业生态系统的可持续管理

21世纪信息科学及其工程技术将加速生态学、分子生物学等现代生物科学的两个前沿学科及其工程技术的发展,在解决人类生存的环境问题和探寻生命本原问题中起推波助澜作用。农业的终极目标是实现对农业生态系统的可持续管理,现代信息工程技术是实现这个目标的核心技术,其中地理信息系统(GIS)、全球定位系统(GPS)和遥感(RS)等3S技术为实现农业生态系统的可持续管理提供了综合的、多维的、动态的,因而也是通晓的和精确的信息资源和技术控制方案,将促进农业真正通向可持续发展之路。

不同育秧方式对水稻苗床N2O排放的影响

基于不同水分管理方式下的水稻育秧方式(分为持续淹水方式下的水育苗床和湿润灌溉水分管理方式下的旱育苗床),研究了不同水稻育秧方式对水稻苗床期N2O排放的影响。研究结果表明:综合不同氮肥施用类型,常规水育苗床系统生育期的N2O平均排放通量介于28.64-34.35μg/(m2.h)。与常规水育方式相比,旱育苗床不同施肥处理的生育期N2O排放总量增加了72%-186%。基于本研究中苗床系统的N2O排放强度,估算出20世纪90年代我国苗床系统的N2O排放总量介于1.46-1.96 Gg/a,占稻田本田N2O排放总量的3%-6%。相对于现在所广泛采用的旱育秧方式,常规采用持续淹水管理方式的水育苗床并增加有机氮肥的投入可以有效地减少水稻苗床期的N2O排放。

An Institutional Innovation for Agricultural Technology Adaptation and Adoption： Rice in West and Central Africa

This paper traces the origins and achievements of the R^seau Ouest et Centre Africain du Riz--ROCARIZ （West and Central Africa Rice Research and Development Network）. The ROCARIZ institutional arrangement showed that rice science is approached from multi-stakeholder perspectives that place end users and entrepreneurs at the center of research for development, and collaboration among rice-based stakeholders can be enhanced and sustained. The ROCARIZ used competitive research grants through multi-stakeholder task forces to generate, adapt, and facilitate the adoption of rice-based technologies and approaches by resource poor households. The grants contributed to： （1） farmer adoption of high yielding and multiple stress resilient lowland NERICAs （New Rices for Africa） （NERICA-L）; （2） producer access to credit and services resulting in increased marketing of quality seed rice, paddy, and grain rice by farmer entrepreneurs and poor rural households; （3） improved skills of stakeholders on the use of impact assessment tools to demonstrate adoption of rice-based technologies; （4） enhanced skills of rice breeders in molecular assisted marker selection to shorten the varietal development process; and （S） experiential learning and sharing to improve access to information and knowledge.

Impacts of soil fertility management on productivity and economics of rice and fodder intercropping systems under rainfed conditions in Odisha,India

Under small and marginal farm conditions,allocation of land exclusively for forages is not possible.Hence,integration of forages in existing crop geometry can ensure production of grain and fodder,simultaneously under rainfed conditions.Afield experiment was conducted to study the effect of different nutrient management practices on rice and fodder intercropping systems under rainfed conditions during 2015-2017.The intercropping system comprised(i)sole rice(R),(ii)rice and cowpea(5:2)(CP)and(iii)rice and ricebean(5:2)(RB)whereas the different nutrient management practices comprised(i)application of farm yard manure(FYM)at 5t ha^(-1)(farmers'practice)(N_(1)),(ii)application of inorganic fertilizer(recommended dose of fertilizer(RDF)of rice,60:30:30 kg ha^(-1) of N:P_(2)O_(5):K_(2)O)(N_(2))and(iii)application of both FYM at 5t ha^(-1) and 50%of RDF inorganic fertilizer(N3).The results of the experiment revealed that the growth attribute such as leaf area was influenced significantly when fodder crops were taken as intercrops because rice plant was getting more nitrogen from soil due to nitrogen fixation of leguminous fodder crops.Among the nutrient management practices,significant differences in leaf area were found beween N2 and and between N_(3)and N_(1)treatments.However,regarding total number of effective tillers,significant differences were found neither between nutrient management practices nor between cropping systems.The rice equivalent yield(REY)based on price(REY_(P))was found to be significantly lower in CP(2615 kg ha^(-1);-6.4%)and RB intercropping systems(2571 kg ha^(-1);-8.0%)than in R monocropping system(2794 kg ha^(-1)).However,the REY based on energy(REY_(E))of CP(2999 kg ha^(-1);+7.3%)and RB(2960 kg ha^(-1);+5.9%)were found to be significantly higher than that of R(2794 kg ha^(-1))irrespective of nutrient management practices.Between different nutrient management practices,the N3 treatment recorded the highest REY_(P)and REY_(E)which was at par with the N_(2)treatment and significantly higher than the N1 treatment irrespective of cropping systems.The combined application of both organic and inorganic sources of nutrients helped to supply nutrients throughout the growing season,which led to improved growth parameters and rice yield.The R monocropping system resulted in more income and rain water use efficiency(RWUE)closely followed by rice and fodder intercropping systems.However,the REYe and energy use efficiency(EUE)of rice and fodder intercropping systems were higher than those of R.Also,fodder helped to meet the requirement of cattle feeding in the off-season.Hence,the intercropping system is advocated in the study zone.Further study can be done on ecosystem services and carbon sequestration potential of the intercropping system,as well as the system's coping ability in response to short drought through observing periodic soil moisture regime in root zone.