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1.
尖孢镰刀菌是土壤中常见的一种镰刀菌,能寄生于多种植物,导致植株萎蔫,也能较长期地腐生于土中,其中的萎蔫专化型是棉花枯萎病的致病菌,在连续栽种感病棉花品种的情况下,该菌每年随病株残体进入土壤后土中菌量随之增多,因而病情逐年加重,即使棉田改种其它早作几十年后再种棉花,,发病率仍然很高[1,4]。有人认为尖抱镰刀菌能在土中长期持留主要归因于其能在多种非致病寄主上生存[4]。前文指出,厚垣抱子的产生是维持其在土中长期存活的原因[3],在有新鲜基质的情况下,厚垣抱子就能很快恢复活性。本文再就土壤因子对尖抱镰刀菌在有机残体上的竟争腐生定殖能力及对该菌在植物残体中腐生存活的影响等,探讨该菌在土壤中的存活与消长。 相似文献
2.
作物覆盖度对土壤侵蚀的影响 总被引：1，自引：0，他引：1
为研究传统耕作模式下坡耕地作物覆盖度对土壤侵蚀的影响,利用冬小麦不同的种植密度和生长期来模拟作物不同的覆盖度情况。采用人工模拟降雨方法测定0,150万,250万,350万,450万株/hm2 5种不同密度处理在不同生育期的覆盖度、地表径流和土壤侵蚀,分析作物覆盖度对土壤侵蚀的影响。结果表明:(1)坡耕地作物种植密度的不同导致覆盖度产生差异,对土壤侵蚀有明显的影响,作物覆盖度一般随种植密度的增加而增加,但如果密度过大,由于生长状况不佳,覆盖度反而变小,表现为7.5万株/hm2时覆盖度最大,种植密度最大的9万株/hm2的覆盖度却不是最大;(2)侵蚀量和径流量与作物覆盖均呈较好的指数函数关系,分别为Y=44.37e-0.09x(p＜0.01),Y=1089.19e-0.02x(p＜0.01),即随作物覆盖度的增加,径流量和侵蚀量减少;(3)土壤侵蚀和地表径流之间存在显著的指数函数关系(R2=0.96)。研究结果对分析传统耕作农地的土壤侵蚀,量化耕作措施因子和准确预测土壤侵蚀,指导农田水土保持有重要意义。 相似文献
3.
及时并准确地估计作物产量，对保障粮食安全、维护世界粮食供应稳定具有重要意义。此前，已有许多研究者使用机器学习方法对作物产量预估进行研究。然而，结合作物的空间分布、使用局部模型进行分析的研究较少；且诸多研究均以年份为时间尺度进行建模，未能精细到作物生长的各个阶段，无法实现作物产量的早期预测。针对以上问题，该研究结合多源遥感数据，利用随机森林（random forest，RF）以及地理加权随机森林（geographically weighted random forest regression，GWRFR）模型对美国县级玉米产量进行建模，探讨全局与局部模型在玉米产量预测方面的性能；并通过将GWRFR模型应用于玉米的各个物候期，获取了玉米产量的最佳提前预测时间。结果表明，GWRFR局部模型的精度（R2=0.87，RMSE=864.21 kg/hm2）高于传统的RF全局模型（R2=0.83，RMSE=994.75 kg/hm2），并且能够较好地克服空间数据的非平稳性，即使在全局模型中加入经纬度作为变量，RF模型的预测效果（R2=0.85，RMSE=890.88 kg/hm2）仍然低于GWRFR模型。对于玉米产量的预测可以提前至收获前2～3个月，即在乳熟期前后就能得到比较准确的预测结果（R2=0.90，RMSE=748.39 kg/hm2）。该研究结果可为大尺度作物产量预估提供一种新的思路，对区域或全球其他作物的产量预测也具有一定的指导意义。 相似文献
4.
基于气候阻力的温室黄瓜蒸腾速率模拟 总被引：1，自引：0，他引：1
在北方地区玻璃温室内，观测黄瓜生长期叶温与温室内微气象因子，利用基于能量平衡方程和水汽扩散理论的叶-气温差方程计算植株气孔阻力(ri)，结合同期气候阻力(r*)和边界层阻力(re)进行分析，结果发现：不同天气条件下ri/re的比值与r*/re比值之间呈极显著正相关关系，晴天时：ri/re=1.207(r*/re)-0.326(n=328，r=0.8055)，阴天时：ri/re=0.169(r*/re)+0.278(n=222，r=0.8076)。根据此拟合方程，以r*/re代替ri/re代入修正后的P-M公式中计算温室黄瓜的蒸腾速率，与直接代入ri值的计算结果比较，结果晴天与阴天条件下的相对误差均<10%，一致性指数达0.96以上，说明利用拟合方程建立的模型模拟效果很好。此模型能够直接利用气象数据计算温室作物气孔阻力并进而计算蒸腾速率，使温室作物蒸腾速率的计算更简单方便，该文结果对同类温室和作物有参考价值。 相似文献
5.
长江中下游地区夏季温室黄瓜冠层温度模拟与分析研究 总被引：3，自引：0，他引：3
根据作物冠层能量平衡原理，建立了以温室内温度、湿度、冠层净辐射等为变量的温室作物冠层温度的模拟模型，并利用实测资料对模型的可靠性进行了检验，同时就温室内部温度、冠层净辐射、蒸腾速率对冠层温度的影响进行了敏感性分析。结果表明：模型能较好地预测长江中下游地区温室作物冠层温度，模型对该地区夏季(2002年6月24至7月12日，梅雨季节)温室内作物冠层温度预测值与实测值的决定系数(R2)和标准误(SE)分别为：0.8321，0.0037℃；建立的温室内部温度、相对湿度、净辐射和作物蒸腾速率的多元线性回归模型，其决定系数(R2)和标准误(SE)分别为：0.9996，0.8829℃；通过敏感性解释因子的分析表明，作物冠层温度对温室内部温度最为敏感，室内温度是预测冠层温度的主要因子。 相似文献
6.
为了探究盐旱胁迫对土壤中氮素分布和棉花生长的影响,通过测坑试验研究滴灌区不同盐分、干旱条件下土壤全氮、硝氮、氨氮的分布和棉花生长情况。试验设置3种盐分梯度的土壤（电导率,EC）：3,6,9 dS/m,分别用T1、T2、T3表示;3个灌水量：2 700,3 600,4 500 m3/hm2,分别用W1、W2、W3表示（4 500 m3/hm2为当地推荐灌水量）。结果表明：当土壤盐分梯度> 3 dS/m时土壤全氮累积量显著高于低盐土壤（P<0.05）,且土壤盐分对棉花花期生长影响较大。土壤的氨氮挥发量和土壤盐分梯度成正比。土壤硝态氮的淋失与灌水量呈正比,与正常灌水量的硝态氮淋失相比,水分胁迫对棉花产量的影响更为严重（P<0.01）。随土层深度的增加,土壤碱解氮以每20 cm土层8%的速度减少。各处理土壤15N残留率为11%~40%,随土壤盐度增加而增加,随灌水量增加而减少,与土壤全氮含量呈正比,与棉花产量呈反比。综上所述,T1W3处理更有利于棉花对氮肥的利用和产量的提高,推荐滴灌区棉花土壤盐度<3 dS/m,灌水量4 500 m3/hm2,可在花期适当提高施肥量以稳定产量。 相似文献
7.
斑潜蝇虫害叶片受害程度对其近红外反射光谱的影响 总被引：4，自引：1，他引：4
为探索实现作物虫害自动监测的方法，采用图像处理和光谱分析技术，测定了斑潜蝇虫害叶片的近红外反射光谱，计算了虫害叶片的破损率，对其破损率和干鲜比与近红外分光反射率的关系分别进行了回归分析。结果表明：在某些波段，叶片的破损率和干鲜比均与近红外分光反射率有较好的相关性。叶片的干鲜比与近红外分光反射率关系的决定系数：黄瓜为R2=0.79(在1452 nm)，番茄为R2=0.70(在1450 nm)。叶片的破损率与近红外分光反射率关系的决定系数，黄瓜为R2>0.81(在1436～1468 nm)，番茄为R2>0.69(在1436～1466 nm)。试验和分析结果证明斑潜蝇虫害叶片的虫害程度能很好地被近红外光谱信息反映。 相似文献
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9.
为从微生态角度探索接种AM真菌对铅污染根际土壤微生物群落代谢特征的影响,以摩西管柄囊霉（Funneliformis mosseae）和幼套近明囊霉（Claroideoglomus etunicatum）为接种菌剂,在温室盆栽条件下以Pb4+含量为0 mg·kg-1、200 mg·kg-1、400 mg·kg-1和800 mg·kg-1土壤种植龙葵（Solanum nigrum）10周后采集根际土壤,采用Biolog微平板法测定龙葵根际土壤微生物群落的代谢变化。结果表明：1）微生物平均代谢活性（AWCD）随铅浓度增加呈降—升—降趋势;接种AM真菌显著提高了铅胁迫下根际土壤微生物的AWCD值,仅中浓度（400 mg·kg-1）下未达显著差异。2）中浓度铅处理能显著提高根际土壤微生物对糖类及其衍生物、氨基酸类、脂肪酸和脂类及代谢产物类四大类碳源底物利用能力;接种AM真菌,高浓度（800 mg·kg-1）铅处理显著提高了根际土壤微生物对氨基酸类底物的利用能力。3）铅胁迫下接种AM真菌提高了根际土壤微生物多样性指数,在中浓度下丰富度指数、Shannon-Wiener多样性指数、Simpson优势度指数均达显著水平。4）主成分分析显示,代谢产物类在PC1和PC2中种类最多,分别为6种和4种;糖类及其衍生物在PC3中种类最多（5种）。5）在铅胁迫和接种AM真菌共同作用下,微生物碳源利用主要受铅浓度调节,并且二者对微生物碳源利用具有显著交互效应。综上可知,接种AM真菌能够提高铅胁迫下龙葵根际土壤微生物多样性指数,增强根际土壤微生物对碳源底物的利用能力。该研究为进一步探究AM真菌强化植物联合修复技术提供了依据。 相似文献
10.
为研究灌水量、施氮量和缩节胺用量对棉花籽棉产量、纤维品质和水肥利用效率的交互影响,于2020年和2021年在南疆库尔勒地区开展大田试验,设置3个灌水量（W1：60%ETc,W2：80% ETc,W3：100% ETc,ETc为作物蒸发蒸腾量）,4个施氮量（N0：0 kg/hm2,N200：200 kg/hm2,N300：300 kg/hm2,N400：400 kg/hm2）和2个缩节胺用量（D1：120 g/hm2,D2：240 g/hm2）。结果表明：灌水量、施氮量和缩节胺用量对籽棉产量、水分利用效率、肥料偏生产力和部分纤维品质指标影响显著（P<0.05）。灌水量、施氮量和缩节胺用量三者交互作用对肥料偏生产力和纤维品质影响显著（P<0.05）。株高、叶面积指数和干物质量也受灌水量、施氮量和缩节胺用量三者交互作用影响。W3N300D2处理籽棉产量最高（2020年为7 578 kg/hm2,2021年为7 173 kg/hm2）,W1N400D1处理水分利用效率和W3N0D2处理肥料偏生产力最高,W3N400D1处理的纤维长度、纤维强度和马克隆值均获得较大值,纤维品质最佳。基于TOPSIS综合评价方法对棉花产量品质和水肥利用效率进行综合评价,100%ETc灌水量、300 kg/hm2施氮量和240 g/hm2缩节胺用量组合最优,可作为南疆棉花适宜的水氮和化控管理模式。研究结果可为南疆棉花水肥高效利用提供理论依据和科学指导。 相似文献
11.
[目的]研究不同盐渍化土壤中枸杞间作红豆草的水盐运移规律及枸杞产量效应,以期为甘肃省引黄灌区枸杞种植模式与盐碱地改良提供理论和技术支撑。[方法]设置枸杞单作和枸杞间作红豆草2种种植模式,非盐化(S_1)、轻度盐渍化(S_2)和中度盐渍化(S_3)3种盐渍化程度,分析不同种植模式和盐渍化程度下土壤水盐运移及枸杞产量。[结果]与枸杞单作相比,枸杞间作红豆草可显著提高3种盐渍化条件下0—20 cm土层土壤含水率,0—120 cm土层土壤含水率表现为枸杞间作红豆草低于枸杞单作,且非盐化(S_1)条件下二者差异最显著(p0.05);0—60 cm土层范围内,枸杞间作红豆草的土壤呈脱盐状态,S_1,S_2,S_3条件下的相对脱盐率分别为6.539,3.078,2.455,而枸杞单作的土壤呈盐分累积状态;随着盐渍化程度的加剧,枸杞鲜果百粒重和产量逐渐减小,其中非盐化(S_1)和轻度盐渍化(S_2)条件下,枸杞间作红豆草的鲜果百粒重、产量均高于枸杞单作,且差异显著(p0.05)。[结论]枸杞间作红豆草在提高表层土壤含水率,降低土壤含盐量的同时,有利于提高枸杞产量,且在非盐化(S_1)条件下效果较优。 相似文献
12.
The determinants of saprotrophic or predatory modes of the nematophagous fungus Arthrobotrys oligospora were investigated in soil microcosms and on solid nutrient media. A sterilized soil amended with 1% w/w alfalfa meal (C:N=32) and inoculated with conidia of A. oligospora, showed lower mycelium biomass and higher specific rate of conidia production in the presence of the bacterivorous nematode Caenorhabditis elegans than in its absence. As few as 10 nematodes g−1 soil were sufficient to enhance spore formation by the vegetative mycelium. Given that the fungus was not limited by available carbon and nitrogen, this indicates that nematodes provide essential growth factors regulating the development of A. oligospora. Carbon mineralisation by A. oligospora, measured as the rate of CO2 production, was found to be 25–35% lower in the presence of 20–60 C. elegans g−1 soil compared to soil without nematodes. This showed that A. oligospora had lower saprotrophic activity in the predaceous phase. Trap formation and nematophagous activity of A. oligospora were observed only where conidia were inoculated on nutrient poor medium (water agar), on low-nitrogen medium (Yeast Carbon Base agar) or on medium containing no amino-acids or vitamins (Czapek-Dox agar). A. oligospora did not form trapping structures when grown on nutrient-rich media containing three amino-acids (l-histidine monohydrocloride, dl-methionine and dl-tryptophan) and vitamins (biotin, calcium pantothenate, folic acid, inositol, niacin, p-aminobenzoic acid, pyridoxine hydrochloride, riboflavine, thiamine hydrochloride). It is concluded that predaceous behaviour of A. oligospora can be regulated either by nitrogen sources or by physiologically active compounds (amino-acids or vitamins) present in nematodes. 相似文献
13.
Macroconidia of Fusarium solani f. cucurbitae were placed into natural soil, incubated for various times, recovered and examined by light and transmission electron microscopy. Lysis of macroconidia and formation of chlamydospores were studied and the fine structure of these propagules and their associated microflora was investigated. The two most obvious features of chlamydospore morphology were the sloughing of outer wall layers and the accretion of micro-fibrillar elements adjacent to the plasmalemma. Chlamydospore formation was partially suppressed by addition of nitrogenous compounds to the soil. 相似文献
14.
H. J. M. Löffler A. Koelman H. B. Nielander B. Schippers 《Biology and Fertility of Soils》1986,2(1):1-6
Summary Addition of 0.1% NH4Cl or 0.1% urea to one of two soils tested had little or no effect in one soil, but resulted in fewer chlamydospores ofFusarium oxysporum present after 6 weeks in the other soil. This was due to reduced formation of chlamydospores and, particularly, to enhanced lysis of chlamydospores. The hypothesis that ammonia was the causal factor was tested. Ammonia evolved from NH4Cl and urea in both soils to the same amount. Since the effects of NH4Cl and urea were different in the two soils, it is concluded that ammonia was not responsible for the reduced number of chlamydospores. Possibly nitrite is involved. 相似文献
15.
The interactions between soil P availability and mycorrhizal fungi could potentially impact the activity of soil microorganisms and enzymes involved in nutrient turnover and cycling, and subsequent plant growth. However, much remains to be known of the possible interactions among phosphorus availability and mycorrhizal fungi in the rhizosphere of berseem clover (Trifolium alexandrinum L.) grown in calcareous soils deficient in available P. The primary purpose of this study was to look at the interaction between P availability and an arbuscular mycorrhizal (AM) fungus (Glomus intraradices) on the growth of berseem clover and on soil microbial activity associated with plant growth. Berseem clover was grown in P unfertilized soil (−P) and P fertilized soil (+P), inoculated (+M) and non-inoculated (−M) with the mycorrhizal fungus for 70 days under greenhouse conditions. We found an increased biomass production of shoot and root for AM fungus-inoculated berseem relative to uninoculated berseem grown at low P levels. AM fungus inoculation led to an improvement of P and N uptake. Soil respiration (SR) responded positively to P addition, but negatively to AM fungus inoculation, suggesting that P limitation may be responsible for stimulating effects on microbial activity by P fertilization. Results showed decreases in microbial respiration and biomass C in mycorrhizal treatments, implying that reduced availability of C may account for the suppressive effects of AM fungus inoculation on microbial activity. However, both AM fungus inoculation and P fertilization affected neither substrate-induced respiration (SIR) nor microbial metabolic quotients (qCO2). So, both P and C availability may concurrently limit the microbial activity in these calcareous P-fixing soils. On the contrary, the activities of alkaline phosphatase (ALP) and acid phosphatase (ACP) enzymes responded negatively to P addition, but positively to AM fungus inoculation, indicating that AM fungus may only contribute to plant P nutrition without a significant contribution from the total microbial activity in the rhizosphere. Therefore, the contrasting effects of P and AM fungus on the soil microbial activity and biomass C and enzymes may have a positive or negative feedback to C dynamics and decomposition, and subsequently to nutrient cycling in these calcareous soils. In conclusion, soil microbial activity depended on the addition of P and/or the presence of AM fungus, which could affect either P or C availability. 相似文献
16.
Radish plants infested with a soil-borne plant pathogen, Fusarium oxysporum f. sp. raphani PEG-4, which is resistant to hygromycin B, were placed on the surface of a soil microcosm containing earthworms (Pheretima sp.). The earthworms ate the radish plants and scattered individual casts everywhere in the burrows. The fungal propagules were detected in the gut of the earthworms and in 26 out of 28 casts. These results suggested that the pathogen could survive passage through the alimentary canal of the earthworms and be disseminated anywhere earthworms wandered. The collected casts were incubated in a moist chamber at 28°C for 14 days, which resulted in a decline in the number of the propagules. The effects of the earthworms on the population dynamics of the pathogen were estimated. The earthworms seemed to cause a decline in total propagules of the pathogen in soil, although they expanded its distribution in soil. 相似文献
17.
The effects of inoculating arbuscular mycorrhizal (AM) fungi on the growth, phosphorus (P) uptake, and yield of Welsh onion (Allium fistulosum L.) were examined under the non-sterile field condition. Welsh onion was inoculated with the AM fungus, Glomus R-10, and grown in a glasshouse for 58?days. Non-inoculated plants were grown as control. Inoculated and non-inoculated seedlings were transplanted to a field with four available soil P levels (300, 600, 1,000, and 1,500?mg P2O5?kg?1 soil) and grown for 109?days. AM fungus colonization, shoot P concentration, shoot dry weight, shoot length, and leaf sheath diameter were measured. Percentage AM fungus colonization of inoculated plants was 94% at transplant and ranged from 60% to 77% at harvest. Meanwhile, non-inoculated plants were colonized by indigenous AM fungi. Shoot length and leaf sheath diameter of inoculated plants were larger than those of non-inoculated plants grown in soil containing 300 and 600?mg P2O5?kg?1 soil. Shoot P content of inoculated plants was higher than that of non-inoculated plants grown in soil containing 300 and 600?mg P2O5?kg?1 soil. Yield (shoot dry weight) was higher for non-inoculated plants grown in soil containing 1,000 and 1,500?mg P2O5?kg?1 soil than for those grown in soil containing 300 and 600?mg?P2O5 kg?1 soil. Meanwhile, the yields of inoculated plants (200?g plant?1) grown in soils containing the four P levels were not significantly different. Yield of inoculated plants grown in soil containing 300?mg P2O5 kg?1 soil was similar to that of non-inoculated plants grown in soil containing 1,000?mg P2O5?kg?1 soil. The cost of AM fungal inoculum for inoculated plants was US$ 2,285?ha?1 and lower than the cost of superphosphate (US$ 5,659?ha?1) added to soil containing 1,000?mg P2O5 kg?1 soil for non-inoculated plants. These results indicate that the inoculation of AM fungi can achieve marketable yield of A. fistulosum under the field condition with reduced application of P fertilizer. 相似文献
18.
土壤水湿状况和肥料碳氮比对稻田肥料氮素转化的影响 总被引：2，自引：0，他引：2
本文应用15N示踪法,测定并探讨了土壤中三种水分状况及四种不同C/N值肥料对肥料氮素转化的影响,试验结果表明:土壤水分和肥料C/N值均对水稻产量有较大的影响,相比之下,土壤水分的影响似更大.水稻对肥料氮的吸收利用率,淹水栽植高于旱植,氮素固定在旱地条件下作用加强,淹水并有一定渗漏的土壤上肥料氮的损失最大,示踪结果说明从土壤渗漏液中淋失的氮素80%以上为土壤固有氮素,相对而言肥料氮的损失较低.试验还表明肥料中碳氮值与肥料氮的吸收利用率之间呈负相关,与肥料残留率呈正相关.此外,本试验还测定了土壤水湿状况和肥料碳氮值在土壤氮素转化中的作用,讨论了当土壤氮素矿化和固定作用相等时,有机肥的碳氮临界值及其实用意义. 相似文献
19.
在华北平原, 外来入侵植物黄顶菊[Flaveria bidents (L.) Kuntze]是一种农田和生态环境中的恶性杂草, 使用除草剂清除势必威胁到农业生产尤其是蔬菜生产的安全性。本课题研究了黄顶菊的不同部位离体茎段和残留部分的恢复再生能力; 并采用土壤培养试验, 研究了含氮量为12.2 g·kg-1的黄顶菊烘干残体和含氮量为23.3 g·kg-1的白三叶草残体在土壤中的分解过程及矿质氮的供应能力, 探讨人工拨除的黄顶菊作为绿肥的可能性。试验表明, 黄顶菊不同部位离体茎段的再生能力达10%~80%, 不同大小的残留部分再生能力达70%~100%。因而人工除草后必须将拔除的黄项菊残体带出田间以防其再生。在整个60 d的土壤培养期间, 黄顶菊和白三叶草残体均表现为施入土壤的前10 d内表观CO2-C日释放量最大, 以后趋于平稳; 但黄顶菊残体处理土壤的CO2-C日释放量一直低于白三叶草。黄顶菊残体处理的土壤微生物量氮高于白三叶草残体处理及土壤对照; 微生物量碳则为黄顶菊残体处理低于白三叶草残体处理, 且与土壤对照相近。在培养的前20 d, 黄顶菊残体分解过程中显著固定了土壤矿质氮素, 培养40 d后的表现为矿质氮释放。黄顶菊残体具有提高土壤氮素营养和微生物量, 增肥土壤的作用, 人工拨除的黄顶菊经灭活处理后可以作为绿肥施入田间。 相似文献
20.
Chlamydospores of Phytophthora cinnamomi were used as inoculum of known density (ID) in an investigation of the rate of jarrah seed germination and the level of infection of seedlings at the various ID's.Inoculum recovery by soil plating was about 2% of the added density. The germination of the jarrah seedlings was accelerated by the increase of the ID, especially at ID of 250 chlamydospores g?1 soil. The nominal LD50 value for jarrah seedlings per chlamydospore inoculum was calculated as 13.0 chlamydospores g?1 soil and the number of viable chlamydospores in the rhizosphere at the highest ID was estimated as 9.1. 相似文献