Rainfall and tillage effects on soil structure after alfalfa conversion to maize on a clay loam soil in New York

Soil degradation is accelerated when perennial crops are converted to annual row crops, primarily due to increased soil disturbance from tillage. Subsequent heavy rainfall may induce soil settling, reduce macroporosity and increase hardsetting upon drying. An experiment involving plow and no-tillage and two simulated rainfall treatments (‘wet’ and ‘dry’) was conducted on Kingsbury clay loam soil in northern New York in 1992 and 1993 to study their effects on soil structure under maize (Zea mays L.) after conversion from alfalfa (Medicago sativa L.), and to evaluate the use of spectral analysis of micropenetrometer observations for studying soil aggregation. Undisturbed soil cores were collected from the row and trafficked and non-trafficked interrow positions at the 0.05 and 0.15 m depths and used for laboratory measurement of soil strength and pore system properties. These well-structured soils show a high contribution (up to 0.15 m³ m⁻³) of macropores to the total porosity of the soil. Soil strength was generally slightly higher for no-till (NT) than plow till (PT), although only significant in 1992. Soil strength in the surface layer did not change significantly with drying. Spectral density patterns did not show strong treatment effects, although distinct peaks reflect 3.0–3.5 mm stable structural units within macroaggregates. Simulated rainfall treatments and tillage treatments generally did not strongly affect measured soil properties, presumably due to stable soil structure. Structurally stable clay loam soils show little effect of tillage or settling on soil physical properties in the first years after alfalfa to maize conversion, and have good potential for long-term annual crop production if properly managed.     

Bound amino acids in humic acids from arable cropping systems

We investigated the varying concentrations of bound amino acids in humic acids (HA) extracted from soils under both crop rotation and continuous cropping of rye. The experiment was created in 1957. Since then, winter rye had been grown continuously and also the sequence of the 7 yr rotation had been started: potato, spring barley, alfalfa, alfalfa, oil seed rape, winter rye, and winter rye. Soils were fertilized with NPK and manure. Continuous cropping of rye increased total acidity of soils and the contents of carboxylic and phenolic groups in HA. The total amounts of the bound amino acids in HA from soils under crop rotation were higher than from continuous cropping of rye. Fertilization with NPK increased the contents of bound amino acids more than manure. Neutral amino acids dominated in all samples of HA, and basic amino acids had the lowest concentrations. In both types of cultivation, glutamic acids, glycine, alanine, valine, and lysine dominated. The proline contents in HA from continuous rye cropping were higher than in HA from soils under crop rotation. The concentrations of β‐alanine and lysine were higher in HA from crop rotation indicating a higher microbial biomass since these compounds are typical constituents of bacteria cell walls.     

太湖地区稻麦轮作农田氮素淋洗特点

通过排水采集器模拟试验研究了太湖地区不同施肥水平下农田N素淋洗特点。结果表明,N的渗漏损失以硝态氮（NO3^--N）为主,并发生在麦季,铵态氮（NH4^ -N)淋洗量则很少,NO3^--N的量占渗漏液总N量的43%-72%,浓度为20-110mg/kg;渗漏水中N的含量与土壤N的淋洗量随施肥量的增加而增加,麦季土壤中NO3^--N肥量的3.7%-12.2%;与纯化肥处理比较,化肥 猪粪处理增加了农田N的淋失,化肥 秸秆处理减少了土壤中N的淋失,与麦田渗漏水相比较,稻田渗漏水除水稻生长早期的部分样品外,NO3^--N和NH4^ -N含量均很低,分别在1mg/kg和0.5mg/kg以下。     

Diversity and abundance of springtails (Hexapoda: Collembola) in soil under 90-year potato monoculture in relation to crop rotation

The monoculture cropping system causes significant changes within the soil ecosystem, which constitutes a habitat for soil-dwelling springtails. Focusing on the response of soil fauna to 90 years of potato cultivation in monoculture the study investigates the abundance and diversity of soil-dwelling springtails, considering changes in the soil environment in relation to five-crop rotation. Another point was the soil quality evaluation using Collembola as bioindicators (QBS-c index). A long-term monoculture experiment was established in Poland in 1923 and has continued uninterruptedly to the present time. Soil samples were taken over a period of three years (2011–2013) to determine collembolan abundance and composition, as well as physical and chemical soil properties.

The study demonstrated that there were greater numbers of Collembola in the long-term monoculture of potatoes, especially before planting time, compared to numbers in a five-field crop rotation. At the same time apparently greater species diversity was found in potato culture within crop rotation. The biological indicator of soil quality based on the occurrence of springtails (QBS-c) has proved useful in assessing changes in soil caused by agrotechnical activities. This index indicated better biological soil quality in the five-field rotation system compared to monoculture.     

Simulating management effects on crop production, tile drainage, and water quality using RZWQM-DSSAT

The objective of this study was to explore if more crop-specific plant growth modules can improve simulations of crop yields, and N in tile flow under different management practices compared with a generic plant growth module. We calibrated and evaluated the Root Zone Water Quality Model (RZWQM) with the Decision Support for Agrotechnology Transfer (DSSAT v3.5) plant growth modules (RZWQM-DSSAT) for simulating tillage (NT — no till, RT — ridge till, CP — chisel plow, and MP — moldboard plow), crop rotation {CC — continuous corn, and CS — corn (Zea mays L.)-soybean [Glycine max (L.) Merr.]}, and nitrogen (N) (SA — single application at preplant, and LSNT — late spring soil N test based application) and manure (SM — fall injected swine manure) management effects on crop production and water quality. Data from 1978 to 2003 from a water quality experiment near Nashua (Nashua experiments), Iowa, USA, were used. The model was calibrated using data from one treatment plot and validated for the rest of the plots. Simulated management effects on annual N loading in tile flow were agreeable with measured effects in 85%, 99%, 88%, and 78% of the cases for tillage, crop rotation (CS vs. CC), N application timing (SA vs. LSNT), and swine manure applications (SM vs. SA), respectively. On average, the LSNT plots were simulated to have 359 kg ha^− 1 higher corn yield compared to SA, when the observed increase was 812 kg ha^− 1. Grain yield simulations were not sensitive to differences between RT and NT, between SM and SA treatments, and between CS and CC. We conclude that considering the uncertainties of basic input data, processes in the field, and lack of site specific weather data, the results obtained with this RZWQM-DSSAT hybrid model were not much better than the results obtained earlier with the generic crop growth module.     

中国热带地区不同作物长期轮作对土壤线虫群落结构及多样性的影响

A field experiment was carried out from 2003 to 2013 in the Wanzhong Farm of the Hainan Island, China, to determine the effects of two long-term banana rotations on the abundance and trophic groups of soil nematode communities in the island. The experiment was set out as a randomized complete block design with three replications of three treatments: banana-pineapple rotation(AB), banana-papaya rotation(BB) and banana monoculture(CK) in a conventional tillage system. Soil samples were taken at depths of 0–10, 10–20 and 20–30 cm, and nematodes were extracted by a modified cotton-wool filter method and identified to the genus level. Nematode ecological indices of Shannon-Weaver diversity(H′), dominance index(λ), maturity index(MI), plant parasite index(PPI), structure index(SI), enrichment index(EI), and channel index(CI) were calculated. A total of 28 nematode genera with relative abundance over 0.1% were identified, among which Tylenchus and Paratylenchus in the AB, Thonus in the BB, Tylenchus and Helicotylenchus in the CK were the dominant genera. The rotation soils favored bacterivores, fungivores and omnivores-predators with high colonizer-persister(c-p) values. Soil food web in the rotation systems was highly structured, mature and enriched as indicated by SI, MI and EI values, respectively. Higher abundance of bacterivores and lower values of CI suggested that the soil food web was dominated by a bacterial decomposition pathway in rotation soils. Nematode diversity was much higher after a decade of rotation.Soil depth had significant effects on the abundance of soil nematodes, but only on two nematode ecological indices(λ and MI).     

A mycorrhizal pathogen (Glomus macrocarpum Tul. & Tul.) of tobacco: effects of long- and short-term cropping on the mycorrhizal fungal community and stunt disease

A crop rotation experiment was conducted on two adjacent tracts of land differing in long-term croppin history (30 year in tall fescue pasture or 3 year in sorghum-sudangrass hybrid (SSGH).. Short-term crops were 2 years in tobacco or low-endophyte (Acremonium coenophialum Morgan-Jones & Gams) tall fescue. Tobacco was grown on all plots in Year 3, and data relating mycorrhizal stunt disease of tobacco and populations of the stunt pathogen, Glomus macrocarpum Tul. & Tul., and of other members of the mycorrhizal fungal community, were taken. Disease incidence was highest with SSGH-tobacco and lowest with fescue-fescue, the other two combinations being intermediate. Mycorrhizal colonization was related to disease occurence. At the beginning of the season, populations of G. macrocarpum were equally high in land with a long-term history of SSGH, regardless of its short-term history; but at the end of the season, populations of G. macrocarpum among the four treatments were proportional to the incidence of disease. Populations of four mycorrhizal fungal species which were high in land with a short-term history of fescue were depressed by production of tobacco. Monocropping of tobacco appeared to narrow the diversity of the mycorrhizal fungal community and increased the proportion which is pathogenic, the overall result being lower productivity of soil for tobacco. Crop rotation of tobacco with fescue decreased the proportion of the mycorrhizal fungal community which is pathogenic and maintained productivity of soil for tobacco.     

基于主成分-聚类分析评价不同轮作模式对土壤肥力的影响

为探明我国西北半干旱区"粮经饲"不同轮作模式的土壤肥力效应,于2017年在宁夏自治区固原市原州区设置玉米-豌豆(C-Pe)、玉米-玉米(C-C)、2龄苜蓿(2A)、高粱-马铃薯(B-Po)、燕麦-玉米(O-C)、马铃薯-燕麦(Po-O)、豌豆-高粱(Pe-B)7种轮作处理模式,研究了不同粮草轮作模式土壤养分、酶活性及可培养微生物群落特征,并进行土壤肥力综合评价。结果表明:(1)不同轮作处理模式对土壤养分影响显著,与其他轮作模式相比,2A模式更有利于土壤养分的累积,而C-C模式增加了对养分的消耗,C-Pe和Po-O模式的有机质、全氮、速效氮、速效磷和速效钾含量高于B-Po和O-C模式,轮作处理对全钾含量影响较小。(2)不同轮作处理模式对土壤酶活性影响显著,2A模式较其他轮作模式显著增加了土壤脲酶和蔗糖酶活性(P<0.05),C-C模式土壤酶活性最低。O-C和Pe-B模式的蔗糖酶、脲酶和碱性磷酸酶活性高于B-Po模式。(3)不同轮作处理模式对土壤可培养微生物数量影响显著,且各轮作模式下土壤微生物数量以细菌占绝对优势,放线菌次之,真菌数量最少,并有明显的土层垂直分布规律,与其他轮作模式相比,2A、C-C和B-Po模式的细菌数量和微生物总数量显著下降(P<0.05),真菌数量显著增加(P<0.05),O-C模式的细菌数量和微生物总数量明显增加,真菌数量降低。(4)运用主成分分析-数值聚类方法对不同轮作模式下土壤养分、土壤酶活性、土壤微生物数量的15个指标进行土壤肥力综合评价,主成分分析提取的2个主成分累计贡献率达89.38%,第1主成分以土壤有机质、全氮、速效氮、全磷、速效磷、速效钾、蔗糖酶、脲酶和碱性磷酸酶贡献最大,达63.56%,第2主成分以细菌数量、真菌数量和微生物总数贡献最大,达25.82%,且各轮作模式在2个主成分上的综合得分排名为2A>Pe-B>C-Pe>O-C>Po-O>B-Po>C-C。再以2个主成分得分进行聚类,将7个模式共分为3类,第1类(2A)土壤综合肥力最好;第2类(Pe-B、O-C、C-Pe、Po-O、B-Po)土壤综合肥力较好;第3类(C-C)土壤综合肥力较差。研究结果为当地耕作方式改良提供理论依据和实践指导。     

改善农学管理措施减少太湖稻麦轮作NH3和NO排放

以稻麦轮作为对象,采用密闭室-通气法和静态箱-化学发光法对太湖地区空白（不施氮肥）、当地常规（农民习惯管理方式）和保产增效（与当地常规相比,改善作物种植、水分和养分管理方式）3个处理下的氨（NH3）挥发和一氧化氮（NO）排放进行田间原位观测,研究保产增效措施对稻麦轮作NH3 挥发和NO排放的综合影响。结果表明,与当地常规相比,保产增效在施氮量减少25%的情况下,总作物产量没有降低,且农学利用率提高了39%;保产增效NH3挥发量在稻季和麦季分别减少了26%和44%;保产增效在稻季NO排放量较低（0.75±0.03 kg N/hm2）,与空白和当地常规均没有显著差异（p<0.05）,在麦季NO排放量则显著降低了49%。因此,保产增效措施不仅能保障高产和提高氮利用率,还能减少NH3和NO排放,值得在太湖地区推广。     

Agronomic Practices at Low Environmental Impact for Durum Wheat in Mediterranean Conditions

The application of conservative agricultural practices such as crop rotation, shallow tillage, and organic fertilizer could usefully sustain crop yield and increase soil fertility, thus playing an important role in the sustainable agriculture. This study was conducted to determine the effects of conservative agronomic practices on yield and quality of wheat. The effects of these practices on soil fertility were further investigated in this four-year study (2005–2008). Two cropping systems, durum wheat in continuous cropping, and in two-year rotation with leguminous crops, were investigated at Foggia (Southern Italy) in rain-fed conditions. Within each cropping system, two levels of crop management were compared: i) conventional, characterized by a higher soil tillage management and mineral fertilizers application; ii) conservative, with a lower soil tillage management and organic-mineral fertilizers. The seasonal weather greatly affected the wheat yield and quality, inducing lower production in years that were characterized by unfavorable climatic conditions. This trend was found when the conventional treatment was applied, both in continuous cropping and rotations. The effects of cropping systems and crop management pointed out the positive role played by the leguminous crops (common vetch and chickpea) in crop rotation. This introduction improved wheat yield in rotation (6.47% compared to the continuous cropping), improved grain protein content (5.88%), and reduced the productive gap between conventional and conservative treatments (9.24 and 14.14% of the wheat in rotation and continuous cropping, respectively). Conversely, the effects of cropping systems and crop management on soil fertility were not very high, since the differences found at the end of the study in total nitrogen values were poor. However, total organic carbon (16.04 and 17.58% for cropping system and crop management, respectively) and available phosphorus values (11.30 and 7.43%) depend on root organic matter contribution, plant biomass residues, and fertilizations. The suitable crop rotation and the sustainable crop management appear important agronomical practices to improve yield and quality of wheat, and may reduce the environmental risks resulting from conventional intensive cropping systems.