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.     

草莓连作土壤灭菌与施用有机肥对根际土壤酚酸及土壤酶活性的影响

针对草莓连作土壤灭菌后与正茬相比草莓植株根系生长受到抑制,研究了连作土壤灭菌与施用不同种类肥料对草莓幼苗（移栽60 d后）根系分泌酚酸及土壤相关酶活性的影响。结果表明：连作土壤灭菌与施用有机肥料处理显著提高了草莓植株根际土壤中酚酸的含量,其中施用蚯蚓粪（经蚯蚓食用处理的牛粪）的增幅显著低于施用牛粪。土壤灭菌处理后施加不同肥料,土壤多酚氧化酶活性均能较快恢复;有机肥较无机肥能显著促进过氧化氢酶活性的恢复;蚯蚓粪较牛粪和无机肥能显著促进土壤脲酶活性的提高;土壤蔗糖酶受土壤灭菌影响显著降低且施加不同肥料对其没有显著地影响。综上所述,对于草莓连作土壤,无论灭菌与否,施用蚯蚓粪较牛粪能减轻连作障碍中的酚酸化感效应,促进脲酶等土壤相关酶活性提高,是缓解连作障碍及连作土壤灭菌对草莓植株生长发育影响的有效措施。     

三七须根粉碎物土壤添加的自毒效应研究

自毒作用是导致三七（Panax notoginseng（Burk.）F.H. Chen）连作障碍的重要原因。本文对三七须根粉碎物土壤添加的自毒效应进行了分析,结果发现：①三七须根粉碎物对其发芽指标呈“低浓度促进,高浓度抑制”的作用趋势,添加量≤10%时不会对发芽率和发芽指数产生显著抑制作用;②三七须根粉碎物对三七植株的出苗率、存苗率具有明显抑制作用;须根粉碎物添加使三七植株的株高、花苔高逐渐降低,茎粗变小,平均小叶数减少,中叶长、宽减小,同时主根的长、宽变小,须根长度变短;③随用量增加,三七植株的地上和地下鲜重、干重及总干重均呈明显下降趋势。三七须根粉碎物土壤添加具有明显的自毒作用。     

长期连作对不同花生品种生长发育、产量与品质的影响

花生是我国重要的油料作物和经济作物,连作障碍已成为花生产业发展面临的突出问题。为解析长期连作对不同花生品种生长发育、产量及内在品质的影响,我们对7个不同花生品种在3年连作地块和10年连作地块的生长发育、产量与产量构成及品质相关指标进行测定分析。结果表明花生出苗率与出苗时间不受连作年限长短影响,且品种间差异不大,但其他形态性状指标、产量与产量构成以及品质指标均受连作年限影响,且不同品种对连作年限的敏感度表现各异。综合生长发育与产量及产量构成各项指标,花育19号、花育20号、花育34号对长期连作最为敏感,花育30号和花育33号敏感度居中;花育26号和花育50号属于对长期连作的耐受品种。花生内在品质同样受连作年限影响,但品种间对连作年限的反应有所差异。     

轮耕对渭北旱塬麦田土壤有机质和全氮含量的影响

【目的】研究由秸秆覆盖免耕、秸秆覆盖深松和秸秆还田翻耕组成的不同保护性轮耕模式对渭北旱塬连作麦田土壤肥力的影响。【方法】2007-2014年在陕西合阳实施夏闲期免耕/深松轮耕（NT/ST）、深松/翻耕轮耕（ST/CT）、翻耕/免耕轮耕（CT/NT）、连续免耕（NT/NT）和连续翻耕（CT/CT） 5种不同耕作模式定位试验,测定并分析2011-2014年小麦收获后不同耕作处理下土壤有机质和全氮变化规律及产量差异。【结果】与连续翻耕相比,连续免耕有利于表层土壤有机质和全氮积累,而免耕、深松和翻耕组成的3种轮耕处理更有利于提高20-40和40-60 cm土层土壤有机质和全氮含量,其中随着耕作年限延长,连续免耕处理下土壤养分逐渐表现出“上层富集,下层贫化”的现象;而免耕/深松轮耕更有利于耕层及耕层以下土壤养分均匀分布。随着轮耕年限增加,各耕作处理0-60 cm土层土壤有机质含量和总量均呈现出整体增加趋势,其中以免耕/深松处理增加趋势比较明显。与2007年相比,免耕/深松、深松/翻耕和翻耕/免耕3种轮耕处理的0-60 cm土层年平均有机质含量增加速率分别为4.53%、3.02%和2.26%,2014年土壤有机质总量分别增加了4.07、2.68和1.65 kg·m^-3。轮耕7年后,免耕/深松、深松/翻耕和翻耕/免耕轮耕处理较连续翻耕处理0-60 cm土层土壤有机质含量分别显著增加25.3%、15.2%和10.2%,有机质总量分别增加31.57%、21.45%和13.94%,其中免耕/深松处理较连续免耕有机质含量增加9.20%,总量增加3.84%。在2011-2014年期间,与连续翻耕相比,连续免耕和3种轮耕处理0-60 cm土层土壤全氮含量及总量均有不同程度增加。其中2014年免耕/深松、深松/翻耕和翻耕/免耕轮耕处理较连续翻耕处理0-60 cm土层土壤全氮含量分别增加17.3%、8.0%和6.4%,氮总量分别显著增加了0.21、0.13和0.09 kg·m^-3,其中,免耕/深松处理较连续免耕全氮含量增加了3.02%,总量减少了2.26%。2011-2014年冬小麦平均产量表现为深松/翻耕＞免耕/深松＞连续翻耕＞翻耕/免耕＞连续免耕,其中深松/翻耕和免耕/深松处理冬小麦平均产量接近,分别较连续翻耕处理显著增产10.36%和9.80%,较连续免耕处理显著增产17.84%和17.24%;翻耕/免耕较连续翻耕处理减产1.59%,较连续免耕处理增产5.08%,但差异不显著。不同保护性轮耕措施下,各土层土壤有机质含量与全氮含量间呈显著正相关;0-20 cm土层有机质含量与轮耕年限呈显著线性相关。【结论】3种轮耕模式较连续翻耕有利于提高0-60 cm土壤有机质和全氮总量,且较连续免耕有利于土壤养分含量在耕层及耕层以下土层均匀分布,其中以免耕/深松轮耕处理效果最优,且增产效应较佳,为渭北旱塬连作麦田较适宜的休闲轮耕模式。     

大棚果蔬连作土壤肥力限制性因子研究

【目的】揭示大棚果蔬连作的土壤肥力限制性因子,为大棚果蔬的连作经营提供参考。【方法】以草莓番茄轮作(RST)为对照,研究草莓连作2年(CS2)、草莓连作3年(CS3)、番茄连作4年(CT4)和番茄连作10年(CT10)4种果蔬种植模式对其根际与非根际土壤养分与酶活性的影响。【结果】与RST相比,连作土壤pH呈酸化趋势,其土壤硝态氮含量有所增加,但也会造成有机质、速效磷的耗竭以及有效态微量元素(锌和铁)的缺失。与轮作相比,连作种植时果蔬根际和非根际土壤的硝态氮含量分别增加了10.3%～30.0%和2.4%～23.2%;有机质减少了4.4%～8.8%和2.8%～7.4%;土壤速效磷降低了5.5%～24.4%和8.7%～25.5%。与轮作相比,CS2处理根际与非根际土壤的有效态锌含量分别减少了36.8%和35.2%;有效态锰有所减少但变化不大;CT4处理有效态铜含量分别减少了43.0%和34.8%;CT10处理有效态锌、锰和铁含量严重缺乏,连作年限越长,土壤质量下降越显著。CS2与CS3处理土壤的过氧化氢酶、脲酶和纤维素酶活性均表现为非根际土壤>根际土壤,而CS2、CS3与CT4处理土壤的蔗糖酶活性则与之相反,均表现为根际土壤>非根际土壤。随连作年限的增加,非根际土壤的过氧化氢酶、磷酸酶和蔗糖酶活性均表现出降低趋势;纤维素酶活性在非根际土壤中表现出增加趋势。微量元素分别与土壤pH和有机质含量有很好的相关性,但与土壤速效氮、磷和钾的相关性不显著。【结论】土壤有效态锌和铁元素的亏缺是土壤肥力的限制性因子。     

天津北部生态区不同种植体系土壤养分调查研究

通过调查和土壤采集测定法研究了天津北部生态区大田和设施菜田土壤养分状况及变化。结果表明:2007年大田土壤有机质和全氮平均含量较1982年均有所提高,分别增加了35.2%、30.5%。2007年土壤有效磷和速效钾含量较1982年分别增长了652.1%、29.2%。设施菜田土壤养分水平高于大田。农田土壤养分增加与农田施肥水平增长有着密切关系。试验对该区农田科学施肥提供了一些参考。     

Stability analysis of farmer participatory trials for conservation agriculture using mixed models

Normally, the data generated from farmer participatory trials (FPT) are highly unbalanced due to variation in the number of replicates of different treatments, the use of different varieties, farmers’ management of the trials, and their preferences for testing different treatments. The incomplete nature of the data makes mixed models the preferred class of models for the analysis. When assessing the relative performances of technologies, stability over a range of environments is an important attribute to consider. Most of the common models for stability may be fitted in a mixed-model framework where environments are a random factor and treatments are fixed. Data from on-farm trials conducted in the Indo-Gangetic Plain (IGP) of South Asia under the umbrella of Rice-Wheat Consortium (RWC) were analyzed for grain yield stability using different stability models. The objective was to compare improved resource management technologies with farmers’ practice. The variance components of an appropriate mixed model serve as measures of stability. Stability models were compared allowing for (i) heterogeneity of error variances and (ii) heterogeneity of variances between environments for farmers-within-environment effects. Mean comparisons of the treatments were made on the basis of the best fitting stability model. Reduced-till (non-puddled) transplanted rice (RT-TPR) and reduced-till drill-seeded wheat using a power tiller - operated seeder with integrated crop and resource management RTDSW(PTOS)ICRM ranked first in terms of both adjusted mean yield and stability.     

小麦–玉米种植制度下长期施钾对土壤钾素Q/I关系的影响

为评价长期施肥条件下土壤钾素容量和强度（Q/I）关系,采用Q/I法研究了小麦–玉米种植制度下3类土壤（塿土、潮土和红壤）,连续15年不施钾（NP）和施钾（NPK）土壤钾素Q/I关系的变化及其参数与土壤性质变化的关系。结果表明,长期施钾土壤K+平衡活度比（AR0）、土壤活性钾（KL）、非专性吸附钾（-△K0）和专性吸附钾（KX）均较不施钾土壤的高,其中,施钾后AR0和-△K0值提高幅度最大的是红壤,分别提高13.78和12.17倍;15年连续施用钾肥对红壤钾位缓冲容量（PBC）影响不明显,塿土和潮土长期施钾处理PBC值显著降低（17 %～20 %）。不施钾土壤K+和Ca2++Mg2+交换自由能（-△G）（13.69～19.33 kJ/mol）高于施钾土壤（12.15～12.81 kJ/mol）;土壤钾素Q/I参数与土壤1 mol/L HNO3浸提K、K+饱和度和有机质含量等存在显著相关关系。土壤钾素Q/I参数能科学评价土壤的供钾状况。连续15年施钾肥土壤供钾能力较高,长期不施钾肥土壤钾素亏缺明显,尤其是潮土和红壤易出现缺钾。     

Soil characteristics,belowground diversity and rates of simazine mineralisation of a New Zealand Gley Soil in a chronosequence under horticultural use

The chemical, physical and biological conditions of a New Zealand Gley Soil was examined on matched sites under long-term permanent pasture or used to grow blackcurrants (Ribes nigrum) for 2, 8, 10 or 20 years. The chemical and physical conditions of topsoils (0–10 cm) were assessed by soil pH, Olsen P, total C, total N, mineralisable N, cation exchange, bulk density, porosity and moisture release characteristics. The biological conditions were assessed from the microbial biomass, soil respiration, catabolic evenness and numbers and diversity of the soil nematode populations. The ability of the soil populations to degrade the triazine herbicide simazine was tested. The particle size distribution confirmed all the sites were very well matched, within 2%, in terms of percentage clay, silt and sand contents, which were 36.5–40.5% clay and 59.5–62.5% silt. Compared with the soil under pasture, that under horticultural use for 2, 8, 10 and 20 years had lower total C and N, lower mineralisable N, lower cation exchange and lower porosity but higher bulk density and particle density. The differences were greater the longer the plots had been under blackcurrant production. Olsen P content was greatest (58 μg P cm⁻³) under the 20-year blackcurrant plots. Changes in biological characteristics were greater than in physical or chemical characteristics. Microbial biomass was 1.73 mg C cm⁻³ under pasture and decreased to 0.87 mg C cm⁻³ after 20 years of blackcurrants. Total nematode populations deceased from 3.89 million m⁻² under pasture to 0.36 million m⁻² after 2 years of blackcurrant production and to 108 000 m⁻² after 20 years. There were similar proportional decreases in bacterial-feeding, fungal-feeding, plant-feeding and omnivore nematodes; however, there was comparatively little change in nematode diversity (Shannon–Weiner) or in microbial catabolic diversity or soil respiration. Despite the decreased microbial biomass, the microbial community under blackcurrant production had enhanced capacity to degrade simazine, as compared with the pasture soil. That capacity to degrade simazine was similar in soils that had grown blackcurrants for 2, 8, 10 or 20 years. Yield of blackcurrants had been maintained in the longer-term sites, despite the marked changes in soil chemical, physical and biological conditions.