排序方式： 共有18条查询结果，搜索用时 15 毫秒
1.
D.?S.?MendhamEmail author S.?Kumaraswamy M.?Balasundaran K.?V.?Sankaran M.?Corbeels T.?S.?Grove A.?M.?O’Connell S.?J.?Rance 《Biology and Fertility of Soils》2004,39(5):375-382
Growth and soil N supply in young Eucalyptus tereticornis stands at two sites in Kerala, India, were examined in response to cover cropping with three legume species (Pueraria phaseoloides, Stylosanthes hamata, and Mucuna bracteata). The effects of legume residues on soil N supply were investigated in a long-term (392 day) laboratory incubation using leaching micro-lysimeters. Residues from the eucalypt and legume species had different rates of net N release during the laboratory incubation. Net N release was significantly related to residue N concentration (R2 =0.94), the C:N ratio (R2 =0.91), the lignin:N ratio (R2 =0.83), and the (lignin + soluble polyphenol):N ratio (R2 =0.95). Nitrogen release rates declined in the order Mucuna > Pueraria > Eucalyptus > Stylosanthes. There was no net N release from Stylosanthes residues during the 392-day laboratory incubation, whereas Mucuna and Pueraria released N throughout the incubation period. Net N release from mixtures of legume and eucalypt residues was not additive in the early phase of the incubation, probably because eucalypt residues initially immobilized a portion of the legume-derived N in addition to the soil-derived N. Legume establishment had no significant effect on tree growth at one site (Kayampoovam), but resulted in depressed tree growth at the lower rainfall site (Punnala) at 18 months. There were no significant treatment effects on growth at Punnala after that time. Cover cropping with legumes during the early phase of forest plantation growth may be a useful mechanism to enhance soil N supply and optimize the synchrony between N supply and tree N uptake. Although these effects did not translate into improved plantation growth in the 3 years of this study, improved soil organic matter and N fertility may help ensure sustainable productivity over several rotations in the future. This study showed that the effect of legumes on N dynamics varies markedly with legume species. This, together with other factors (e.g. competition with trees, N fixation capacity), will be important in selecting suitable species for cover cropping in forest plantations. 相似文献
2.
3.
Sindhuja Sankaran Juan José Quirós N. Richard Knowles Lisa O. Knowles 《American Journal of Potato Research》2017,94(6):658-663
Plant emergence and stand establishment are key indicators of early crop development that are routinely assessed in potato agronomy and crop improvement research. The standard method for evaluating emergence is through manual plant counts at regular intervals. In this proof-of-concept study, unmanned aerial vehicles integrated with multispectral imaging were used for high-throughput evaluation of crop emergence under field conditions. High-resolution aerial imaging was performed at 15 m above ground level to capture data from potato plots of two varieties (‘Alturas’ and ‘Payette Russet’) in which the seed had been treated with different concentrations of growth regulators (including non-treated controls). The treatments resulted in differences in plant emergence and establishment. The images were collected at 32, 37, and 43 days after planting (DAP). Image-based features such as plant count, SUM-NDVI, and SUM-BINARY were computed from normalized difference vegetation index (NDVI) images for each treatment plot using ArcGIS®. The Pearson’s correlation coefficients (r) were significant (p < 0.05) between image-based plant counts (r = 0.82) and SUM-NDVI (r = 0.62-0.73) with that of manual plant counts for both varieties, especially at early growth stages (32 DAP) when differences in emergence among treatments were more pronounced. The treatment effects on plant emergence and establishment were effectively resolved in the aerial multispectral images. Selection of the pertinent polygon threshold area to eliminate noise in delineating individual plants during image processing was important for resolution of treatment effects. The data shows that the technique can be applied in potato establishment evaluation. 相似文献
4.
Yongsheng Si Sindhuja Sankaran N. Richard Knowles Mark J. Pavek 《American Journal of Potato Research》2017,94(1):88-93
Potato tuber length to width (L/W) ratio is a critical crop trait evaluated during the development and selection of new cultivars to assess the effects of environment and management on tuber size and shape. The major challenges in manual measurement of L/W ratio are that it is labor-intensive, time consuming, and sometimes inconsistent. A high-throughput, digital image-based method for estimation of L/W ratio was developed in this study. Tests were conducted using tubers from a local retail market (red, white and russet) and from a field experiment with Payette Russet cultivar specifically designed to alter tuber size and shape. An image processing algorithm was developed to process the potato tuber images and the L/W ratio data from the images were compared to manual caliper measurements. A high accuracy in tuber L/W ratio estimation was consistently observed using image-based analysis. Among the different potato cultivars, red cultivars had a lower average accuracy in L/W ratio estimation of 94%, while other cultivars exhibited 96% and higher average accuracies. 相似文献
5.
With a view to study the effect of intercropping and plant geometries in peanut cv. VRI-1 , a held experiment was conducted at Area Agronomic Centre, Tamil Nadu Co-operative Oilseeds Growers' Federation Limited, Neyveli, India during winter season 1989, (November 89–April 90) under irrigated condition. Three intercrops viz., pigeonpea, sunflower and finger millet were tested at two plant geometries viz., paired rows of 40/20 cm and 45/15 cm. The study indicated that pigeonpea was compatible with peanut and their combination resulted in higher peanut kernel equivalent yield and higher profit. Sunflower and finger millet depressed the base crop yield and found to be unsuitable for intercropping in peanut. Base crop yield was not influenced by the plant geometries. 相似文献
6.
In this study, we assessed the variability in pod, seed traits and oil content of 24 accessions of Pongamia pinnata collected from different parts of the Andaman and Nicobar Islands, India. The experiment was conducted at the Central Agricultural Research Institute, Port Blair during 2010 to 2011. The variability studies for pod and seed traits revealed that, the accession CPT-6 collected from New Wandoor in South Andaman recorded the maximum values for eight traits viz. pod length （75.51 mm）, pod width （34.62 mm）, pod thickness （17.55 mm）, 100 pod weight （770.33 g）, seed width （21.23 mm）, 100 seed weight （377.00 g）, oil percentage （43.92%） and germination percentage （94.7%）. However, the maximum seed length （26.46 mm） was recorded from CPT 2 and the maximum pod-seed ratio was obtained from CPT 13 and CPT 4 （2.50 and 2.44 respectively）. The phenotypic and genotypic coefficients of variations were also close to each other for all traits, but the 100 pod and seed weight exhibited higher phenotypic and genotypic coefficient of variation than the other traits. Estimates of broad sense heritability ranged from 0.30 （for seed length） to 0.95 （pod length） and genetic ad- vance as percent of the mean ranged between 11.66% and 57.40% with seed length giving the lowest value and 100 pod weight giving the high- est value. Both the phenotypic and genotypic correlation between pod length, pod width, pod thickness, 100 pod weight, seed width and 100 seed weight and between pod thickness, 100 pod weight, seed width, 100 seed weight and germination percentage were found to be strong. On the basis of non hierarchical Euclidian cluster analysis, 24 accessions were grouped into six clusters. The maximum numbers of seven accessions were included in cluster VI. The maximum intra cluster distance （10.238）shown by cluster VI and the maximum inter cluster distance （17.021） between V and HI followed by III and II （15.942）. Among the six clus- ters formed the cluster III recorded maximum oil percentage, 100 pod weight, 100 seed ,weight, pod length, pod thickness, pod width, seed width and. germination percentage, while cluster V recorded maximum pod seed ratio and germination percentage. The present findings suggest that the crossing between accessions of cluster V and cluster III will result in a wide spectrum of variability in subsequent generations. 相似文献
7.
P. K. Chandrasekhara Pillai R. C. Pandalai T. K. Dhamodaran K. V. Sankaran 《New Forests》2013,44(4):521-532
The effect of nitrogen addition and weed management on fibre properties of wood from 6.5-year-old Eucalyptus grandis and E. tereticornis from intensively managed short-rotation plantations were investigated. Trees for analyses were sampled from plots with zero nitrogen input (n = 4), plots with high level (187 kg N ha?1) nitrogen input (n = 4), plots from which weed growth was not removed throughout the rotation (n = 4) and plots from which weeds were removed periodically (n = 4). Fibre characteristics were evaluated on wood samples collected from base, breast height, 50, 75 and 100 % of merchantable bole height of trees. Though N input and weed management improved tree growth significantly irrespective of species, the treatment effects did not cause any significant change in fibre characteristics such as fibre length, fibre diameter, lumen width and wall thickness. Longest and widest fibres were observed at the outer most radial portion of wood in all cases. In general, within tree fibre length varied significantly along the radial direction of wood. Fibre diameter, lumen width and wall thickness lacked any specific pattern between species and treatments. Runkel ratio and felting and flexibility coefficients values showed high pulping quality of wood irrespective of species and treatments. The study concluded that the fibre properties that influence pulpwood quality of Eucalyptus have not been affected by silvicultural practices, like fertilizer input and weed management, aimed at improving productivity of short-rotation eucalypt plantations. 相似文献
8.
Some diseases of forest tree seedlings in India caused by Sclerotium rolfsii and Rhizoctonia solani1
Leaf blight of Bombax ceiba and B. insigne caused by Sclerotium rolfsii and collar rot of B. ceiba and Ailanthus triphysa caused by Rhizoctonia solani are reported for the first time from India. 相似文献
9.
Xu J Peng C Sankaran VG Shao Z Esrick EB Chong BG Ippolito GC Fujiwara Y Ebert BL Tucker PW Orkin SH 《Science (New York, N.Y.)》2011,334(6058):993-996
Persistence of human fetal hemoglobin (HbF, α(2)γ(2)) in adults lessens the severity of sickle cell disease (SCD) and the β-thalassemias. Here, we show that the repressor BCL11A is required in vivo for silencing of γ-globin expression in adult animals, yet dispensable for red cell production. BCL11A serves as a barrier to HbF reactivation by known HbF inducing agents. In a proof-of-principle test of BCL11A as a potential therapeutic target, we demonstrate that inactivation of BCL11A in SCD transgenic mice corrects the hematologic and pathologic defects associated with SCD through high-level pancellular HbF induction. Thus, interference with HbF silencing by manipulation of a single target protein is sufficient to reverse SCD. 相似文献
10.
K. Kandiannan C. Kailasam K. K. Chandaragiri & N. Sankaran 《Journal of Agronomy and Crop Science》2002,188(2):138-140
Black pepper (Piper nigrum L.) is an important spice used in cooking and medicine. It is cultivated in more than 20 countries in Asia, Africa and Latin America. India is a major producer, consumer and exporter of black pepper. Leaf area (LA) is an indicator of crop growth and productivity. This study was undertaken to develop a method of estimating the individual LA of black pepper directly without the necessity for time‐consuming area measurements. Ten black pepper lines were used in the study. Ninety matured leaves were collected from each line and an allometric relationship was derived by logarithmic transformation between actual leaf area (ALA) measured using the electronic leaf area meter LI‐3000 A (LI‐COR, Inc., Lincoln, NB) and leaf length (LL). The correlation coefficient (r) between ALA and LL ranged between 0.8692 and 0.9644 and the standard error (S.E.) between 0.0822 and 0.1149. The allometric models for 10 lines were: Panniyur 1, LA=0.7114 (LL)1.8409; Panniyur 2, LA=0.3692 (LL)2.067; Panniyur 3, LA= 0.6148 (LL)1.8838; Panniyur 4, LA=0.8355 (LL)1.7694; Sreekara, LA=0.8984 (LL)1.6692; Subhakara, LA=0.8384 (LL)1.738; Panchami, LA=0.3691 (LL)2.0749; Pournami, LA=0.4487 (LL)1.9718; Kottanadan, LA=0.3474 (LL)2.0634; P‐24, LA=0.7579 (LL)1.654. These allometric models were used to calculate LA, which was then compared with the actual LA, and the correlation coefficient (r) between them was found to be > 0.99. These allometric models can be used to estimate the LA of individual leaves of black pepper. The approximate total LA of a vine can be obtained using following formula: total leaf area of black pepper vine (cm2) = number of laterals per vine × number of leaves per lateral × leaf area of individual leaf. 相似文献