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1.
为实现干旱区绿洲土壤含水量的快速、准确监测,利用采集自渭干河-库车河绿洲的84个表层(0~10cm)土壤样本,通过利用电磁感应仪(EM38)将所测解译后数据代替实测土壤含水量数据,将高光谱反射率重采样为Landsat8卫星遥感波段反射率,在选取光谱特征参数、提取敏感波段的基础上,利用偏最小二乘回归(PLSR)方法建立土壤含水量模型,将最优估算模型应用于遥感影像,实现研究区土壤含水量遥感反演。研究结果表明:(1)利用EM38所测水平模式土壤表观电导率与土壤含水量拟合效果最优,能够代替实测土壤含水量进行后续建模分析。(2)相比3种单一的光谱特征指数,利用多种光谱特征指数所建土壤含水量估算模型的建模效果更优,其干、湿各季建模集决定系数R~2大于0.7,均方根误差(RMSE)均小于0.5%,RPD均大于2,能够作为有效手段估算干旱区绿洲土壤含水量。(3)不同季节土壤含水量遥感反演值与实测值决定系数R~2均大于0.6,均方根误差(RMSE)均小于0.6%,显示了较高的预测精度,证明利用电磁感应技术与高光谱相结合能够实现对干旱区绿洲土壤含水量的精准、高效监测。  相似文献   

2.
A combination of dune-scale observation to distinguish psammophyte distribution, field experiments to determine gradients of soil moisture and physicochemical properties, and controlled quantitative manipulation for psammophytes water use traits was employed to study an arid desert margin area in China. This study aims to: (1) interpret the survival mechanisms of plants in arid desert ecosystems, especially for pioneer species; (2) interpret the links among distribution pattern, stress-gradients, and water use traits; (3) discuss the mechanisms and probable succession processes under natural fixation for artificial ecosystem rehabilitation; and (4) discuss the possibility of recognizing quantified water use traits as a predictor to compare the variations in adaptability among different species. We classified seven psammophytes into three major types in terms of water use: prodigal, moderate, and frugal plants. Results showed that vegetation cover of all the dominant species, including shrubs and herbs, was negatively correlated with diurnal transpiration at rhizosphere moisture (P < 0.01, R2 = 0.94). Herbaceous pioneer species (e.g., Agriophyllum squarrosum) survive harsh environments (shifting, hot and arid surface of dunes) by prodigal water use (high transpiration rate), low species cover, and fast production (high water use efficiency, which peaks at low soil moisture). By contrast, intrusive species (e.g., Eragrostis poaeoides) behaved as frugal plants to survive drought, thereby maintaining high vegetation cover and biomass, as well as soil water equilibration.  相似文献   

3.
为了提高HYDRUS-2D模型在暗管排水中的模拟精度,提出了虚拟土层(VSL)和实际开孔面积(AHA)两种方法来代替HYDRUS-2D在暗管排水中的暗管原有渗透边界(PSB)。研究表明:VSL和AHA模型的模拟值与实测值具有较好的一致性;土壤含盐量平方根误差（RMSE）分别为0.757、0.966 g·kg-1,决定系数(R2)分别为0.977和0.964;土壤含水率的RMSE分别为0.007、0.008 cm3·cm-3,R2分别为0.885和0.794。此外,VSL在模拟排水方面(RMSE=9.48L,R2=0.93)和模拟排盐方面(RMSE=0.225 kg,R2=0.922)的模拟精度均高于AHA和PSB,可见,VSL更适用于暗管边界。进一步建立了VSL的环宽（RW）与其饱和导水率（Ks）之间的经验公式(R2=0.99,P<0.01),当模拟区域和暗管布局变化时,该经验公式可用于确定VSL的模型参数,其模拟结果可用于指导相关地区的暗管布局。  相似文献   

4.
The objective of this study was to investigate the potential of native Thai species for reclaiming salt-affected areas in Thailand. Plant species diversity in Nakhon Ratchasima Province in northeast Thailand, and their soil characteristics (texture, electrical conductivity (ECe), exchangeable sodium percentage (ESP), and pH) were measured. A total of 19 species in 16 genera of 12 families were found, among which the most abundant species belonged to the Poaceae and Cyperaceae families. The highest values of ECe were found near the surface (0–20?cm) with an average range between 30–80?dS?m?1, while lower values in the range of 15–25?dS?m?1 were found at lower depths (20–100?cm). Soil conditions in the subplots with plant coverage showed lower ECe and ESP when compared to plots without vegetation. Seeds from the three most frequently occurring species, including Azima sarmentosa, Gymnosporia mekongensis, and Buchanania siamensis, were then tested for germination at different salinities. Seeds of all three species germinated at high salinities, from 25–45?dS?m?1, with total germination ranging 40–90%. Together with the ability to germinate at high salinities, these native species showed deep, rapid root elongation, likely to escape high surface ECe levels (approximately the top 30?cm). Planting these species in areas with vegetation coverage would aid successful reclamation of saline areas. Reclaiming salt-affected soils will not only improve local farmer’s economic status, but can also reduce the extent of deforestation, benefiting the entire ecosystem.  相似文献   

5.
渭干河—库车河三角洲绿洲棉田土壤盐分估算及遥感反演   总被引：1，自引：0，他引：1  
基于研究区的野外采样数据与Landsat 8遥感影像提取的增强型植被指数,构建渭干河—库车河三角洲绿洲棉田土壤盐分估算模型,并对土壤盐分的空间分布格局进行预测。结果表明:(1)由土壤含盐量与增强型归一化植被指数(ENDVI)构建的线性回归模型(y=-56.494x+22.687)拟合效果最好(R2=0. 886,RMSE=0. 907)。(2)通过选取的82个采样点,依据最佳遥感反演模型,预测出研究区土壤含盐量在9.33～26.99 g·kg-1之间变化,平均值为17.42 g·kg-1,标准差为2.30 g·kg-1,预测结果与土壤盐分的实测值较为一致。(3)利用地统计分析方法制作研究区棉田土壤盐分的空间分布图,分析可知土壤盐分从绿洲内部向外围呈逐渐增加的趋势。  相似文献   

6.
Pristine® (pyraclostrobin + boscalid) is a fungicide registered for the control of alternaria late blight in pistachio. A total of 95 isolates of Alternaria alternata collected from orchards with and without a prior history of Pristine® sprays were tested for their sensitivity towards pyraclostrobin, boscalid and Pristine® in conidial germination assays. The EC50 values for 35 isolates from orchards without Pristine® sprays ranged from 0·09 to 3·14 µg mL?1 and < 0·01 to 2·04 µg mL?1 for boscalid and Pristine®, respectively. For pyraclostrobin, 27 isolates had EC50 < 0·01 µg mL?1 and six had low resistance (mean EC50 value = 4·71 µg mL?1). Only one isolate was resistant to all three fungicides tested, with EC50 > 100 µg mL?1. Among 59 isolates from the orchard with a history of Pristine® sprays, 56 were resistant to pyraclostrobin; only two were sensitive (EC50 < 0·01 µg mL?1) and one was weakly resistant (EC50 = 10 µg mL?1). For the majority of these isolates EC50 values ranged from 0·06 to 4·22 µg mL?1 for boscalid and from 0·22 to 7·74 µg mL?1 for Pristine®. However, seven isolates resistant to pyraclostrobin were also highly resistant to boscalid and Pristine® and remained pathogenic on pistachio treated with Pristine®. Whereas strobilurin resistance is a common occurrence in Alternaria of pistachio, this is the first report of resistance to boscalid in field isolates of phytopathogenic fungi. No cross resistance between pyraclostrobin and boscalid was detected, suggesting that Pristine® resistance appears as a case of multiple resistance.  相似文献   

7.
选取新疆阿拉尔市典型极端干旱区为研究对象,利用土壤高光谱特征对土壤电导率进行反演。为了准确快速检测土壤电导率,通过获取南疆阿拉尔市红枣种植区土壤电导率和高光谱信息,在去包络线处理基础上,分别采用相关性分析法和连续投影算法（SPA）筛选特征波长,并建立特征波长与土壤电导率的偏最小二乘回归模型,使用均方根误差(RMSE)、决定系数（R2）以及相对分析误差（RPD）对不同处理方法的模型效果进行评价。结果表明,基于原始光谱直接使用相关性分析法的预测精度RMSE=0.85566,R2=0.7479,RPD=2.7569;通过去包络线处理使用相关性分析筛选特征波长后,模型的预测精度RMSE=0.44490,R2=0.9500,RPD=6.4510;基于原始光谱使用SPA选择特征波长后,模型的预测精度RMSE=0.31178,R2=0.9707,RPD=8.4445;通过去包络线处理使用SPA选择特征波长后,模型的预测精度RMSE=0.30173,R2=0.9764,RPD=9.3215。综上,说明SPA方法具有较强的特征波长选择能力,基于去包络线处理+SPA的偏最小二乘回归反演模型的预测精度最好,可实现新疆阿拉尔地区土壤电导率的快速检测。  相似文献   

8.
Stem-end rot, caused by Lasiodiplodia theobromae, is an important postharvest disease of papaya in Brazil. The use of fungicides is one of the main disease management measures. However, there are no data available on the sensitivity of L. theobromae to thiophanate methyl (methyl benzimidazole carbamate), the most common fungicide used in papaya orchards in northeastern Brazil. Thus, the effective concentration that results in 50 % of mycelial growth inhibition (EC50) of 109 isolates, representing five populations of the pathogen was estimated in vitro. Seven components of fitness were measured for the 10 isolates with lower and high values of EC50. Of the 109 isolates, 20.2 % were resistant to the fungicide with EC50 values greater than 300 μg ml?1, whereas the remaining 79.8 % were sensitive with an average EC50 of 1.87 μg ml?1. The EC50 values for the resistant isolates were significantly (P?≤?0.05) higher than those for the sensitive isolates. When the fitness components were evaluated, only in relation to the spore production was significant difference among sensitive and resistant isolates, and resistant isolates showed sporulation capacity significantly lower than the S isolates, indicating a fitness cost.  相似文献   

9.
为研究干旱区棉田在滴灌淋洗配合协同排水下的土壤盐平衡变化规律及微生物群落丰度特征,在新疆典型干旱盐碱区（141团）进行野外排水试验,试验设置暗管与竖井双因素协同排水,X轴方向五水平（距离竖井0、15、30、45 m和60 m,记为T1、T2、T3、T4和T5）,Y轴方向三水平（距离暗管0、5 m和7.5 m,记为P1、P2和P3）,分析土壤电导率与地下水位、土壤微生物之间的关系。结果表明,进行淋洗试验后,0~700 cm土层土壤电导率整体降低,200~400 cm土层脱盐最明显,最低达到0.9254 dS·m-1,全生育期平均脱盐率为70%,在距离暗管5 m、距离竖井45 m处的土壤脱盐效果最佳。此外,全生育期地下水埋深呈现先减小后增大的趋势,下降最大幅度达到2 m,且地下水位对土壤盐分的影响具有滞后性,土壤中微生物Chao1指数、多样性指数和丰富度指数均随土壤电导率降低而上升。研究表明,滴灌淋洗配合暗管与竖井排水有利于降低土壤深层盐分、控制地下水位、提升土壤微生物群落多样性,有利于推进干旱区盐渍化农田改良及恢复废弃耕地。  相似文献   

10.
氯苯醚酰胺[N-(2-(2,4-二氯苯氧基)苯基)-3-(二氟甲基)-1-甲基-1H-吡唑-4-酰胺,Y13149]是由华中师范大学基于药效团连接碎片虚拟筛选策略(PFVS)快速发现的新型琥珀酸脱氢酶抑制剂类(SDHIs)化合物。采用菌丝生长速率法,测定了该创制化合物的农药生物活性。结果表明:氯苯醚酰胺对真菌具有较广的抗菌谱,对供试10种植物病原真菌均具有较好的抑制活性,EC50值在0.008~15.25 mg/L之间,其对立枯丝核菌的抑制活性最强,但对辣椒疫霉和链状腐霉活性较弱。田间试验表明,氯苯醚酰胺对水稻纹枯病具有较好的防治效果,有效剂量75 g/hm2时的平均防效为79.6%,其防效总体略好于噻呋酰胺(75 g/hm2的平均防效为77.3%)。此外,氯苯醚酰胺对采自浙江和江苏两省的125株水稻纹枯病菌的EC50值分布在0.002~0.259 mg/L之间,且呈近似正态单峰曲线,平均EC50值为(0.021 ±0.008) mg/L,因此可将其作为水稻纹枯病菌对氯苯醚酰胺的敏感性基线,用于田间抗药性监测。  相似文献   

11.
This study was conducted in 58 producer‐field locations in Manitoba from 2003 to 2006 to understand how cropping practices influence Fusarium graminearum inoculum levels on stubble of various crops, including wheat, collected from the soil surface. Colonies per m2 (CN) were determined and converted to base‐10 logarithm values (log10CN). Mean log10CN of the sampled field for various crops and groups of crops grown in the 3 years prior to sampling were tested to find significant differences. Average log10CN values were also used to determine significant differences between tillage systems and the effect of number of years. Average log10CN values for zero and minimum tillage systems were not different but were significantly higher than values for conventional tillage. A series of three crop rotation scenarios were tested using weighted log10CN values for crop, tillage, their interaction and their squared terms in step‐wise regression models to identify which model was the best predictor of log10CN. This was selected as the cropping practice index (CPI) model and was expressed as: CPI = 1·98423 + 0·55975 (C2 × C1 × T)2 + 0·4390 (C2 × T)2, where C1, C2 and T represent the weighted log10CN values for crops grown 1 and 2 years previously and tillage system, respectively. R2 value for this model was 0·933 (P < 0·0001). The reliability of the CPI model was tested using jack‐knife full cross‐validation regression. The resulting R2 was 0·899. The CPI model was tested using data collected from seven wheat fields in 2006 (R2 = 0·567). The relationship between CPI and FHB index (R2 = 0·715) was significant.  相似文献   

12.
This study compares two methods for evaluating precipitation effects on wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) yield, which have been cultivated for 30?years under two different climate conditions (semi-arid and Mediterranean). The distribution and amount of precipitation were indexed and their relationship with the corresponding crop yields (1984–2013) was investigated. The concentration index (CI), i.e. the contribution of the days of greatest precipitation to the total amount of precipitation, was also calculated as an alternative approach. Both methods were used to analyze the whole crop growing season, from planting to harvest, and for two critical growth stages, germination and anthesis. It was observed that there was a significant correlation between yield and the average daily precipitation (ER; rwheat=0.74** and rbarley = 0.75**) during the whole growing season, irrespective of the crop type, whereas there was no significant impact on crop yield due to the non-uniformity of precipitation distribution (UR). However, when a critical stage like anthesis was evaluated over a shorter period, a significant correlation between UR and crop yields (rwheat=0.56** and rbarley=0.64**) was found. The results indicated that these indexes are very effective for predicting crop yields based on their association with final yield within critical growth stages. In addition, it was also found that a proposed model using both indexes (ER and UR), with high correlation (r?=?0.84**) can be very effective in estimating crops performance. The results also showed that the sensitivity of crop yield to the uniformity of precipitation during the critical growth stages was lower than when the whole growing season was considered. The CI index was less effective in reflecting the distribution of precipitation in the semi-arid and Mediterranean conditions compared with the UR.  相似文献   

13.
为了解西藏林芝地区气象因子对小麦条锈病的影响及其流行动态,2016年采用五点取样法对林芝地区小麦条锈病的发病情况进行监测,通过相关性分析、逐步回归C(p)统计法和线性回归等方法,分析了病情指数与气象因子的关系,并结合时间和病情指数建立了病害预测模型。结果表明,在林芝地区,温度X_1、湿度X_2均与小麦条锈病病情指数Y呈极显著相关,降雨量X_3与病情指数Y呈显著相关;线性回归方程为:Y=-482.5991+19.7494X1+3.7974X2-0.8439X3。根据模拟情况选择的病害流行动态方程为Y=1/e~((0.914t+0.385)),决定系数为0.952,模型的拟合效果较好,表明该模型能够为林芝地区小麦条锈病的预测预报提供有效的参考依据。  相似文献   

14.
The antifungal properties of two phosphonates (fosetyl-Al and a fertilizer) and acibenzolar-S-methyl (ASM) were evaluated to assess their potential for protecting grapevine leaves against grapevine mildews (Plasmopara viticola and Erysiphe necator), and to determine their effects on the development of various mildew isolates, taking into account the inter- and intra-species variability of the pathogens. The phosphonates directly and significantly inhibited the growth of these pathogens. By contrast, ASM had no direct effect on spore production and growth of P. viticola and of E. necator at 1.9 mM. Applied before inoculation, the mean EC50 of ASM was 0.50?±?0.04 mM and 1.00?±?0.07 mM for downy and powdery mildew isolates, respectively. The EC50 of the fosetyl-aluminium (FOS) was 0.50?±?0.02 mM for downy mildew and the EC50 for powdery mildew varied depending on the genetic group under consideration (0.89?±?0.32 mM for group B 3.30?±?0.46 mM for group A, respectively). The EC50 of the potassium phosphonate fertilizer (PK2) was 0.96?±?0.45 mM for downy and 6.9?±?0.76 mM for powdery mildew isolates. These compounds showed differences in their efficacy depending on the variability of mildews and could be an alternative or additional method to traditional pest management in the grapevine.  相似文献   

15.
本试验利用Gram-Schmidt（GS）变换将Sentinel-1A雷达影像与Sentinel-2A多光谱影像进行融合,并分析雷达影像、多光谱影像及融合影像各波段与吉林省白城市表层土壤含盐量的相关性,建立研究区土壤含盐量的反演模型,对研究区土壤含盐量进行制图。研究结果表明：Sentinel-1A 的VH、VV波段后向散射系数与研究区土壤含盐量均呈显著正相关,可用作土壤盐碱化监测的遥感数据源;合适的数学变换可以提升Sentinel-1A、Sentinel-2A及融合影像与土壤含盐量的相关性,其中,Sentinel-1A的VV波段与Sentinel-2A第5 波段融合后,其二次方变换与土壤含盐量的相关系数达到0.820;引入合适的盐分指数可以有效改善Sentinel-2A及融合影像与土壤含盐量的相关性,其中,融合影像的盐分指数(D2D4)/D3与土壤含盐量相关系数达到0.889;利用融合影像及盐分指数(D2D4)/D3建立的研究区土壤含盐量反演模型Y=86.260X-66.206X2-5.312,模型决定系数达到0.791,均方根误差为1.884 g·kg-1,表明将Sentinel-1A雷达影像与Sentinel-2A多光谱影像进行融合来提升土壤含盐量反演精度的方法切实可行。  相似文献   

16.
Combined applications of cyanobacteria with soil fixing chemicals were investigated to generate artificially induced biological soil crust (BSC). Polyvinyl alcohol (PVA) and Tacki-Spray (TKS7) chemicals composed of bio-polysaccharides and tackifiers were examined under laboratory conditions. Following singular applications of chemicals, the mean weight diameter values of soil treated with TKS7 were 1.4–2.5 times higher than those of soil treated with PVA and thus TKS7 was selected for further tests for application with cyanobacteria (Nostoc Vaucher ex Bornet &; Flahault, Phormidium Kützing ex Gomont, and Scytonema arcangeli Bornet ex Flahault). Combined application of cyanobacteria and different concentrations of TKS7 enhanced soil aggregate stability, resulting in mean weight diameter values of 0.58–0.69 mm and was comparable to TKS7 singular application (0.18–0.40 mm). Surface hardness values were also highly improved by the combined application of cyanobacteria with TKS7 (4.5 MPa) compared to singular treatment of cyanobacteria (2.3 MPa). In addition, superabsorbent polymer (SAP) was applied as a water-holding material and nutrient supplement in soil. The SAP promoted cyanobacterial cell growth under dry conditions. Chlorophyll a content of soil was improved by the addition of SAP (CST1: 2.93 µg g?1) compared to singular treatment of cyanobacteria (C: 2.25 µg g?1). These results suggest that combined application of cyanobacteria with TKS7 and SAP can induce BSC formation faster than singular application of cyanobacteria. The novel method presented herein can be applied to restoration of degraded soils in arid and semiarid areas.  相似文献   

17.
采用温度植被干旱指数法(MTVDI)与荒漠化指数法(DDI),利用2016年4月、9月的Landsat数据对毛乌素沙地腹部的土壤水分进行反演,并与实测的土壤水分进行对比检验,将所反演的土壤含水量图划分为4个等级,基于此分析了2个时期毛乌素沙地腹部的旱情土壤水分分布变化。结果显示：(1)4月份MTVDI指数与0~10 cm、10~20 cm、20~30 cm土层土壤含水量的R2值分别为0.656、0.646、0.637,整体高于9月份R2值0.457、0.436、0.431,MTVDI能够较好地反映毛乌素沙地腹部土壤表层水分,且精度较高;(2)荒漠化指数DDI与MTVDI结合建立二元线性回归模型监测区域土层0~10 cm深度含水量,平均相对误差为10.95 %;(3)4月份,研究区0~10 cm表层土壤含水量5%~10%区域占总面积的53.72%以上,达到了6 256 km2,含水量偏低,需要加强当地水资源管理。  相似文献   

18.
Seventy three isolates of Pythium aphanidermatum obtained from cucumber from four different regions of Oman and 16 isolates of muskmelon from the Batinah region in Oman were characterized for aggressiveness, sensitivity to metalaxyl and genetic diversity using AFLP fingerprinting. Twenty isolates of P. aphanidermatum from diverse hosts from different countries were also included in the study. Most isolates from Oman were found to be aggressive on cucumber seedlings and all were highly sensitive to metalaxyl (EC50 < 0·80 µg mL?1). Isolates from cucumber and muskmelon were as aggressive as each other on both hosts (P > 0·05), which implies a lack of host specialization in P. aphanidermatum on these two hosts in Oman. AFLP analysis of all isolates using four primer–pair combinations resolved 152 bands, of which 61 (~40%) were polymorphic. Isolates of P. aphanidermatum from Oman and other countries exhibited high genetic similarity (mean = 94·1%) and produced 59 different AFLP profiles. Analysis of molecular variance indicated that most AFLP variation among populations of P. aphanidermatum in Oman was associated with geographical regions (FST = 0·118; P < 0·0001), not hosts (FST = –0·004; P = 0·4323). These data were supported by the high rate of recovery (24%) of identical phenotypes between cucumber and muskmelon fields in the same region as compared to the low recovery (10%) across regions in Oman, which suggests more frequent movement of Pythium inoculum among muskmelon and cucumber fields in the same region compared to movement across geographically separated regions. However, recovering clones among regions and different countries may imply circulation of Pythium inoculum via common sources in Oman and also intercontinental spread of isolates.  相似文献   

19.
Downy blight, caused by Peronophythora litchii, is an important disease of lychee (litchi) plants in China. The in vitro sensitivities of various asexual stages of P. litchii to the three carboxylic acid amide (CAA) fungicides dimethomorph, flumorph and pyrimorph were studied with four single‐sporangium isolates. None of the three fungicides affected zoospore discharge from sporangia, but they strongly inhibited mycelial growth (mean EC50 values of 0·075, 0·258 and 0·115 mg L?1, respectively); sporangial production (mean EC50 values of 0·085, 0·315 and 0·150 mg L?1, respectively); germination of cystospores (mean EC50 values of 0·140, 0·150 and 0·645 mg L?1, respectively); and germination of sporangia (mean EC50 values of 0·203, 0·5 and 0·743 mg L?1, respectively). As mycelial growth was the most sensitive stage to dimethomorph and pyrimorph, it was chosen to test baseline sensitivities to the three fungicides. In 2007, from 131 isolates collected in Fujian, Guangdong and Guangxi provinces, 127, 116 and 113 isolates were used to establish baseline sensitivity for dimethomorph, flumorph and pyrimorph respectively. Isolates from different provinces exhibited similar baseline sensitivity to the same fungicide. Baseline sensitivities to dimethomorph, flumorph and pyrimorph were distributed as unimodal curves, with mean EC50 values of 0·082 (± 0·01), 0·282 (± 0·047), and 0·115 (± 0·032) mg L?1, respectively. This information will serve as a baseline for tracking future changes in sensitivities of P. litchii populations to these three CAA fungicides.  相似文献   

20.
The brown planthopper (BPH) is an important pest in rice. Rice losses due to BPH's damage are often more than 10% of yield. Assessments on loss rates from BPH are now basically dependent on experiential indices. However, early assessments on rice yield losses using hyperspectral data are still rare. In this study, reflectance from rice canopy was measured in net cages after different densities of BPH release. Results showed that reflectance in the near-infrared region (750–1000 nm) from milk grain stage, and in 400–531 nm and 567–705 nm from mature grain stage was closely related to BPH density. These spectral indices: red-edge parameters (λr, Dλr, Sλr), ratio of the maximal reflectance in green (490–560 nm) to minimal reflectance (640–740 nm) in red (RGREEN/RRED), ratio of the near-infrared peak (RNIR) to RRED, normalized difference vegetation index between RNIR and RRED and soil-adjusted vegetation index (SAVI) from both milk and mature grain stages, indicated BPH densities well. As expected, rate of loss in rice grain was higher with increasing BPH density. SAVI, Dλr, Sλr and reflectance at 760 nm (R760) from milk grain stage were significantly correlated with rates of loss in panicle, and 1000-grain weight and multiple-linear regression models for detecting loss rate were established. The hyperspectral reflectance from rice at milk grain stage can be used to assess rice yield losses due to BPH and improve management policies.  相似文献   

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