土壤基质势调控对温室滴灌番茄土壤水分分布和产量的影响

【目的】指导设施蔬菜生产中科学合理地利用滴灌技术进行灌溉。【方法】采用小区试验的方法,以冬春茬番茄为研究对象,布置了7个不同土壤基质势阈值的试验,在番茄开花坐果期和结果期分别控制滴头正下方20 cm深度土壤基质势在-15和-15 kPa(S1)、-15和-30 kPa(S2)、-15和-45 kPa(S3)、-25和-25 kPa(S4)、-30和-15 kPa(S5)、-30和-30 kPa(S6)以及-30和-45 kPa(S7),研究了日光温室滴灌土壤基质势调控下土壤水分随时间变化及空间分布的规律,以及番茄产量、畸形果率和灌溉水利用效率等。【结果】①控制滴头正下方20 cm深度土壤基质势可以明显影响0～100 cm深度土壤水分状况。②在番茄开花坐果期,当土壤基质势阈值控制在-30 kPa或更高时,番茄根系主要吸收利用0～60 cm深度以上范围的土壤水分,70 cm深度以下土壤水分基本不变,0～60 cm深度土壤体积含水率平均为28.6%,为田间持水率的84%,60～100 cm土壤体积含水率平均为36.2%,为田间持水率的90%。③番茄进入结果期后,当土壤基质势阈值控制在-25～-15 kPa时,整个土体土壤含水率基本保持在田间持水率的77%～91%,根系主要吸收利用0～60 cm深度以上范围的土壤水分,70 cm深度以下土壤水分消耗缓慢;当土壤基质势阈值降低到-45～-30 kPa时,根系吸收利用到80～100 cm深度的土壤水分,整个土体土壤含水率不断降低,降低到田间持水率的60%～66%。④不同处理番茄产量、畸形果率和灌溉水利用效率有明显差异,其中S3和S7处理番茄产量高,S5处理产量低;S1、S3和S4处理的畸形果率大,S6和S7处理的畸形果率低;S1处理的灌溉水利用效率最低,S7处理的灌溉水利用效率最高。【结论】日光温室少量高频滴灌条件下,当滴头正下方20 cm深度土壤基质势阈值开花坐果期控制在-30 kPa、结果期控制在-45 kPa时,整个土体土壤水分状况基本良好,番茄的产量高,畸形果率低,灌溉水利用效率高。     

基于无人机遥感影像的覆膜农田面积及分布提取方法

针对基于无人机遥感的覆膜农田识别研究甚少的现状,该文以云南省昭通市鲁甸县为研究区,获取了研究区中地表类型复杂程度不同的2幅航空影像(复杂区影像和简单区影像)作为试验数据,利用灰度共生矩阵对原始航片影像进行纹理特征提取并选择纹理特征最佳提取参数;然后基于随机森林算法进行纹理特征重要性评价,优选纹理特征,结合原始数据进行最大似然初步分类;运用众数分析进行分类后处理;最后结合图像形态学算法与面积阈值分割法提取出了最终的覆膜农田面积及分布。通过试验结果发现,依据该文提出的方法,复杂区和简单区覆膜农田识别的总体精度、Kappa系数、产品精度、用户精度和面积误差分别达到了94.84%、0.89、92.48%、93.39%、0.38%和96.74%、0.93、97.39%、94.63%、1.95%。该文提出的融合监督分类和图像形态学算法的覆膜农田提取方法可以简单、快速的将地膜连成块,形成覆膜农田对象,进而通过面积阈值分割法获取高精度的覆膜农田分布信息。该方法可以为精准覆膜农田识别算法的发展提供参考。     

双季机插稻不同产量水平群体的产量构成特征研究

为明确双季机插稻产量构成特征及高产协同规律,促进双季稻机插栽培技术的发展,以4个早稻(株两优30、两优287、中嘉早17和中早35)和4个晚稻(H优518、五丰优T025、五优308和天优华占)品种(组合)为试验材料,研究双季机插稻中产(7 000~8 250 kg·hm^-2)、高产(8 250~9 000 kg·hm^-2)和超高产(>9 000 kg·hm^-2)3个产量水平群体的产量及产量构成特征。结果表明,随着双季机插稻产量水平的提高,有效穗数、每穗粒数和总颖花量均呈显著增加的趋势,结实率和千粒重总体上差异较小;产量与群体总颖花量呈极显著正相关,要实现9 000 kg·hm^-2以上的产量,每平方米颖花量需达到42 000以上;从中产到高产,双季早晚稻总颖花量的增加均主要依靠穗数的增加,从高产至超高产,早稻总颖花量的增加仍可以通过适当增加穗数实现,而晚稻总颖花量的增加应在适当增加穗数的基础上提高每穗粒数。以较多的穗数和较大的穗型协同产出较高的总颖花量,同时保证正常的结实率和千粒重,是双季机插稻超高产基本特征。本研究结果为双季机插稻高产栽培提供了理论依据与实践参考。     

天然富硒土壤上三种蔬菜对硒的吸收与转化差异

【目的】研究对硒 (Se) 不同敏感性蔬菜对天然富硒土 (Se ≥ 0.4 mg/kg) 中硒的吸收和转化差异,为富硒土壤生产富硒蔬菜提供理论与技术指导。【方法】以大蒜、芥菜和菠菜三种蔬菜为试验材料,在全硒含量为0.29、0.58、0.98、2.07 mg/kg的四种土壤上进行了盆栽试验 (依次标记为Se_0.29、Se_0.58、Se_0.98、Se_2.07),并测定四种土壤中不同形态硒的含量。芥菜和菠菜于生长40 d、53 d、68 d和82 d后取样,测定蔬菜可食部分硒含量;于生长97 d后收获,分为根部和地上部。大蒜于生长42 d、68 d、82 d、120 d后取样,测定地上部硒含量;于生长165 d后收获,分为根部、鳞茎和叶。测定供试蔬菜总硒含量、有机硒含量,计算不同硒含量土壤上蔬菜对硒的吸收和转化系数。【结果】三种蔬菜中芥菜的生长对土壤硒最为敏感,芥菜可食部位生物量鲜重以Se_0.29处理最高,菠菜和大蒜均以Se_0.58处理最高,与Se_2.07处理均达显著差异。三种蔬菜地上部硒含量在整个生育期总体呈现增加的趋势,不同生育期均表现为大蒜 > 芥菜 > 菠菜。收获期三种蔬菜各部位的硒含量随着土壤硒含量 (0.29～2.07 mg/kg) 的增加而增加,表现为Se_2.07 > Se_0.98 > Se_0.58 > Se_0.29,Se_2.07处理的菠菜地上部和地下部硒含量分别是其Se_0.29处理的8.63倍和7.10倍,芥菜是12.25倍和23.29倍,Se_2.07处理大蒜鳞茎和叶部硒含量是Se_0.29处理的39.92倍和4.90倍;可食部位硒含量为大蒜 (7.25～289 μg/kg) > 芥菜 (1.22～14.9 μg/kg) > 菠菜 (0.73～6.30 μg/kg),均表现为地下部 > 地上部,Se_2.07处理菠菜根部硒含量是茎叶的4.80倍,芥菜是12.06倍,大蒜是8.22倍。在富硒土壤Se_0.98和Se_2.07处理条件下,大蒜和芥菜能从土壤中富集硒,吸收系数是菠菜的3.06～8.47倍和1.58～5.8倍,均达到了富硒蔬菜标准 (≥ 0.01 mg/kg)。三种蔬菜可食部位有机硒含量占总硒比例为73.5%～84.7%,并随土壤硒含量的增加而增加,其中Se_2.07与Se_0.29处理差异显著;蔬菜硒含量不但与土壤总硒含量相关,而且与有效态硒含量呈显著正相关。【结论】蔬菜种类和土壤硒含量均影响蔬菜硒的吸收、转化和富集。三种蔬菜对土壤硒的敏感性以芥菜最强。蔬菜硒含量和可食用部位有机硒的转化率均随着土壤硒含量的增加而增加,与土壤总硒含量和有效态硒含量呈显著正相关。富硒能力为大蒜 > 芥菜 > 菠菜,在天然富硒土壤上生长的大蒜和芥菜硒含量易达到富硒蔬菜标准,而菠菜未显示出富硒能力。因此,虽然土壤硒含量高影响了大蒜和芥菜的生长,但大蒜和芥菜具有较强的将硒转移到可食部位的能力,可作为富硒蔬菜生产。     

基于生态系统格局变化的东西部结合区生态服务价值评价——以珠江—西江经济带为例

[目的]以珠江—西江经济带为例,分析典型东西部结合区生态系统格局变化特征以及对其生态系统服务价值进行评价,为积极构建区域生态安全格局和开展生态补偿研究提供科学依据。[方法]基于珠江—西江经济带2000—2015年生态系统类型数据,采用生态系统类型年均变化率、生态系统类型转移矩阵研究其生态系统格局变化特点;参考生态系统服务价值估算方法,对研究区近15 a来的生态服务价值进行评价与分析。[结果]①2000—2015年珠江—西江经济带以森林和农田生态系统为主,生态系统空间分布格局较稳定,变化的部分主要体现在东部人工表面生态系统的扩张上。②近15 a间农田和草地生态系统面积下降最多,湿地下降较少,其余生态系统类型面积均有不同程度地增加。生态系统类型转换主要发生在森林、农田和人工表面生态系统三者之间。③2000—2015年珠江—西江经济带生态服务价值减少了14.55亿元,其中草地生态系统服务价值下降最多,森林生态系统服务价值增加最多。④珠江—西江经济带各县区生态服务价值空间分布格局稳定,但东部地区单位面积生态服务价值有持续下降的趋势。[结论] 2000—2015年珠江—西江经济带东部生态系统格局变化对其生态服务价值下降产生了较大影响。今后在生态建设方面需重点合理控制东部人工表面生态系统面积的扩张速度,预防其生态服务价值持续下降。     

Postharvest heat disinfestation treatments of mango fruit

Postharvest heat disinfestation treatments have emerged over the past decade as viable non-chemical control methods for fruit flies in mango fruit around the world. The physiological responses of mango fruit both during and following a heat treatment determine the eventual eating quality of the fruit. This review describes the methods used to heat treat mango varieties for insect disinfestation. The physiological effects of heat treatments, particularly pretreatment conditioning and hot water treatments, on the fruit are covered in detail.     

Budgets for root-derived C and litter-derived C: comparison between conventional tillage and no tillage soils

Placement of plant residues in conventional tillage (CT) and no-tillage (NT) soils affects organic matter accumulation and the organization of the associated soil food webs. Root-derived C inputs can be considerable and may also influence soil organic matter dynamics and soil food web organization. In order to differentiate and quantify C contributions from either roots or litter in CT and NT soils, a ¹⁴C tracer method was used.To follow root-derived C, maize plants growing in the field were ¹⁴C pulse-labeled, while the plant litter in those plots remained unlabeled. The ¹⁴C was measured in NT and CT soils for the different C pools (shoots, roots, soil, soil respiration, microbial biomass). Litter-derived C was followed by applying ¹⁴C labeled maize litter to plots which had previously grown unlabeled maize plants. The ¹⁴C pools measured for the litter-derived CT and NT plots included organic matter, microbial biomass, soil respiration, and soil organic C.Of the applied label in the root-derived C plots, 35–55, 6–8, 3, 1.6, and 0.4–2.4% was recovered in the shoots, roots, soil, cumulative soil respiration, and microbial biomass, respectively. The ¹⁴C recovered in these pools did not differ between CT and NT treatments, supporting the hypothesis that the rhizosphere microbial biomass in NT and CT may be similar in utilization of root-derived C. Root exudates were estimated to be 8–13% of the applied label. In litter-derived C plots, the percentage of applied label recovered in the particulate organic matter (3.2–82%), microbial biomass (4–6%), or cumulative soil respiration (12.5–14.7%) was the same for CT and NT soils. But the percentage of ¹⁴C recovered in CT soil organic C (18–69%) was higher than that in NT (12–43%), suggesting that particulate organic matter (POM) leaching and decomposition occurred at a higher rate in CT than in NT. Results indicate faster turnover of litter-derived C in the CT plots.     

Estimating the Fate of De-icing Salt in a Roadside Environment by Combining Modelling and Field Observations

Predicting the environmental effects of de-icing salt requires knowledge of the pathways taken by salt from on-road application through spread to the surroundings to deposition and fate in the roadside environment. This study described differences in chloride deposition and distribution in soil with increasing distance from the road by means of field observations and modelling. The dynamic modelling approach successfully represented the spread of de-icing salt from road to surroundings, deposition in the roadside environment and the subsequent infiltration into roadside soil. The general decrease in soil chloride content with distance from the road was described by differences in salt deposition, soil physical properties, vegetation properties and snow characteristics. The uncertainty in model predictions was highest in areas close to the road due to a complex combination of high salt deposition, snow-ploughed masses and road runoff. The exponential decline in salt deposition with distance from the road could not be justified close to the road. Different types of field investigations were applied in a calibration procedure to establish reasonable ranges for the most influential model parameters. Measured electrical resistivity reflected well the changes in simulated chloride content in soil during winter and spring when chloride concentrations were high. However, during summer or periods with low chloride concentrations the measured resistivity was substantially lower than simulated values, as it reflected the total contamination level in soil.