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... grid was placed on top of the potato at one metre from the ground and only those sections more than half filled with green leaves were counted by observing vertically above to avoid parallax error. In sole potato, the grid was placed half way on each side of the potato row to sample two plants (Figure 1). In intercropped potato, two grid positions were used, one on either side of the potato row since in some potato clones, branches extend beyond 80 cm on either side of the row (Figure 1). ...
Context 2
... sole potato, the grid was placed half way on each side of the potato row to sample two plants (Figure 1). In intercropped potato, two grid positions were used, one on either side of the potato row since in some potato clones, branches extend beyond 80 cm on either side of the row (Figure 1). Two measurements were made per plot. ...
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Potato is the 4 th major vegetable crop in our country but more than 90% of the seed is imported which costs heavy economic burden on the foreign exchange. Further, imported germplasm is not well adapted to local climatic conditions and is vulnerable to different types of diseases. In vitro manipulations have proved their worth not only for the mas...
Citations
... The fraction of field covered by crop leaves (Eqs. (6) and (7)) was calculated from Mottes (2013) using the reported relation by Haverkort et al. (1991) and Cadersa and Govinden (1999) with a default light extinction coefficient for cropland, k ext ¼ 0:62 (À) (Zhang et al., 2014), and a 'maximum soil cover' LAI of a ¼ 3 m 2 m À2 (Allen and Pereira, 2009 from the FAO-56 procedure); setting fr fieldÀcovered to 1 for LAI ! a. ...
The inventory model ‘PestLCI Consensus’, originally developed for temperate conditions, estimates initial pesticide emission fractions to air, to off-field surfaces by drift deposition, and to field crop and field soil surfaces according to crop foliar interception characteristics. Since crop characteristics and application techniques differ in tropical conditions, these aspects need to be included in the model in support of evaluating pesticide emissions under tropical conditions.
Based on published literature, a consistent set of crop foliar interception fractions was developed as function of crop characteristics and spraying techniques for tropical crops. In addition, we derived drift deposition fractions from published drift experiments specifically conducted under tropical conditions. Finally, we compiled a consistent set of pesticide emission fractions for application in life cycle assessment (LCA).
Foliar interception fractions are strongly influenced by the spraying technique, particularly for hand-operated applications. Drift deposition fractions to off-field surfaces were derived for air blast sprayer on papaya and coffee, for boom sprayer on bean and soybean, for aerial application on soybean, sorghum, millet, corn and cotton, and for hand-operated application on cotton. Emission fractions vary for each combination of crop and application method. Drift deposition curves for missing crop-application method combinations can only partly be extrapolated from the set of considered combinations.
Overall, our proposed foliar interception fractions and drift deposition fractions for various crops grown under tropical conditions allow to estimate pesticide emissions in support of assessing the environmental performance of agrifood systems in LCA with focus on tropical regions.
... The frame was divided into 100 equal rectangles of 0.075 m × 0.090 m. The grid was placed above the potato canopy at 1 m from the ground and only those rectangles more than half filled with green leaves were counted by observing vertically above to avoid parallax error (Cadersa and Govinde, 1999). The grid was placed half way on each side of the potato row to sample three plant positions. ...
We designed a model to quantify the canopy cover dynamics in potato (Solanum tuberosum L.). It describes the dynamics during the build-up phase, maximum cover phase, and decline phase of canopy development through five parameters defining timing of three phases and maximum canopy cover (v max). These five parameters were estimated for 100 individuals of an F1 population, their parents, and five standard cultivars, using data from six field experiments, and used to estimate secondary traits, related to duration and area under the canopy cover curve for the three phases. The duration of the canopy build-up phase (D P1) was rather conserved, but the duration of maximum canopy cover (D P2) and the decline phase (D P3) varied greatly, with late maturing genotypes having longer D P2 and D P3 and thus a higher area under the canopy cover curve (A sum). High genetic variability coupled with high heritability was recorded for end of canopy senescence (t e), D P2 and A sum. Strong positive phenotypic and genetic correlations were observed between D P2 and t e , v max or A sum indicating that genotypes with longer D P2 could be indirectly obtained by selecting for these traits. Several quantitative trait loci (QTLs) were detected for model traits explaining the variance by up to 74%. Clustering of many QTLs were found on position 18.2 cM on paternal linkage group V with major additive effects. Many additional QTLs with minor effects were mostly associated with maternal linkage groups. Our model approach could be used to exploit available genetic variability in canopy cover dynamics of potato.
... La couverture du sol par chacune des cultures est calculée en utilisant la relation reportée par Haverkort et al. (1991) et Cadersa and Govinden (2000). Selon leurs travaux, la couverture du sol vaut 100 quand la culture intercepte 82% de la lumière incidente (Cadersa and Govinden 2000;Haverkort et al. 1991 ...
... La couverture du sol par chacune des cultures est calculée en utilisant la relation reportée par Haverkort et al. (1991) et Cadersa and Govinden (2000). Selon leurs travaux, la couverture du sol vaut 100 quand la culture intercepte 82% de la lumière incidente (Cadersa and Govinden 2000;Haverkort et al. 1991 ...
Aujourd'hui encore, les utilisations agricoles de pesticides génèrent des pollutions des cours d'eau qui posent des problèmes environnementaux et sanitaires. Afin de limiter et d'anticiper ces pollutions, il est nécessaire de disposer de méthodes d'évaluation des effets des systèmes de culture sur la pollution par les pesticides des eaux de rivière. Dans certaines zones, telles que les zones volcaniques tropicales, cette connaissance des effets des pratiques des agriculteurs qui cultivent des fruits et légumes (horticulteurs) sur la ressource en eau est extrêmement limitée. L'objectif de cette thèse est de développer une méthode d'évaluation des effet des systèmes de cultures sur la contamination par les pesticides de l'exutoire d'un bassin versant qui soit adaptée aux conditions de l'horticulture en zone volcanique tropicale. Pour cela, nous avons sélectionné un petit bassin versant de 131 ha sur lequel deux dispositifs de suivis ont été mis en oeuvre entre 2011 et 2013: (1) un suivi des pratiques agricoles auprès des agriculteurs du bassin versant et (2) un suivi du régime hydrologique et de la pollution de l'eau par les pesticides à son exutoire. En raison de la complexité agronomique, géologique et hydrologique des bassins versants volcaniques tropicaux horticoles, et afin de produire un outil d'évaluation générique, nous avons développé un modèle agro-hydrologique de transferts de pesticide : WATPPASS. Il synthétise les connaissances sur le fonctionnement agro-hydrologique des bassins versants et simule les effets des pratiques agricoles sur les processus mis en cause dans les transferts de pesticides. WATPPASS reproduit correctement le fonctionnement hydrologique du bassin versant d'étude et les types de contamination de pesticides observés à l'exutoire. Les écarts par rapport aux mesures sont analysés et discutés et des améliorations du modèle sont proposées. WATPPASS est ainsi un outil performant qui peut servir d'outil d'évaluation des effets des systèmes de culture sur la qualité de l'eau, en particulier pour classer des scénarii d'évolution des systèmes de culture à l'échelle de bassins versants. La méthodologie proposée a permis d'identifier les molécules dont les usages actuels sont à risque ainsi que les principales combinaisons de facteurs engendrant des pollutions.
... Receiving sunlight by the plants and using that in plant biomass indicates the fundamental processes which control the crop yield (Purcell et al. 2002). Hence, one of old methods in assessing plants yield is to measure the received light by the plant and calculate the yield in its transformation into dry matter (Cadersa and Govinden 1999). Photosynthetically active radiation (PAR) reception method by the plant ghosting is among the main determining fac tors in ghosting photosynthesis and crop yield (Stewart et al. 2003). ...
Considering the increase in global population and its results, especially the need for food, various grains and mostly wheat have more come into the consideration. Hence, studying this valuable plant and methods to increase its yield are of great essence. The following research tries to study various cultivation densities effects on Rasad wheat growth indices through in-time plate split pattern on base of completely randomized block in three replications, in Ardabil IAU research greenhouse during 2011. In this research, treatments included three cultivation densities, in which first treatment was complete density of 43 plants; second treatment was ½ of complete density (22 plants) and the third treatment was 1/3 of complete density (15 plants). Specific leaf area (SLA), leaf area ratio (LAR), net assimilation rate (NAR), relative growth rate (RGR), crop growth rate (CGR), total dry weight (TDW), leaf dry weight (LDW), Leaf area index (LAI) and leaf weight ratio (LWR) indices were measured. Results suggested that, all studied traits had the highest value in ½ densities (22 plants). Considering the tests, ½ density (22 plants) and density of 43 plants had better stability and yield, comparing to 1/3 density of (15 plants).
... Receiving sunlight by the plants and using that in plant biomass indicates the fundamental processes which control the crop yield (Purcell et al., 2002). Hence, one of old methods in assessing plants yield is to measure the received light by the plant and calculate the yield in its transformation into dry matter (Cadersa and Govinden, 1999). Photosynthetically active radiation (PAR) reception method by the plant ghosting is among the main determining factors in ghosting photosynthesis and crop yield (Stewart et al., 2003). ...
To study the effect of light levels on the growth of wheat, was conducted in Ardabil IAU research greenhouse during 2010. The research was carried out through in-time plate split pattern on base of completely randomized block in three replications with two treatments. First treatment in normal light conditions and the treatment of light was red. Results suggested that in leaf area index (LAI) treatment No. 2 had a higher yield in absorbing sunlight and red light led into treatment No. 2 to produce more leaves.In crop growth rate (CGR) red light had a negative effect on plant dry matter accumulation. To put it another way, red light caused treatment No. 2 to have a lower CGR comparing to treatment No. 1. In relative growth rate (RGR) treatment No. 1 which was exposed to normal sunlight had a higher weight increase during growth period, comparing to treatment No. 2 which was exposed to red light. In net assimilation rate (NAR) treatment No.1 (normal light) produces more dry matter comparing to the treatment No. 2 (red light); that is, normal light has a better photosynthetic efficiency in plant.
... Solar radiation interception by plants and its utilization in biomass production shows essential processes that control the growth and yield of the crops (Purcell et al., 2002). Therefore, one of the methods for evaluating the performance of the crops has been traditionally the measurement of intercepted light by plants and the calculation of the efficiency of its conversion to dry matter (Cadersa and Govinden, 1999) so far that the yield loss induced by the occurrence of environmental stresses can be explained by monitoring the pattern of radiation interception by canopy during growth period (Zanetti et al., 1999). On the other hand, the period during which the plants are able to intercept radiation by their canopies can be extended by selecting cultivars with suitable maturing period duration (Purcell et al., 2002). ...
... The frame was divided into 100 equal rectangles of 0.075 m × 0.090 m. The grid was placed above the potato canopy at 1 m from the ground and only those rectangles more than half filled with green leaves were counted by observing vertically above to avoid parallax error (Cadersa and Govinde, 1999). The grid was placed half way on each side of the potato row to sample three plant positions. ...
We investigated the potential of a model-based approach to assist in the genetic analysis of the environment-sensitive, quantitative crop trait canopy cover in potato (Solanum tuberosum L.). We used a model based on beta functions to analyze the genotype×environment interactions related to the dynamics of canopy cover. The model equations describe three phases of canopy growth: build-up phase (P1),
maximum cover phase (P2), and decline phase (P3). The model has five parameters: t m1 indicates the transition from accelerating to diminishing growth during P1, t 1 marks the end of P1 when canopy cover attains its maximum level v max , t 2 marks the end of P2 when canopy cover starts to decline, and t e represents the end of the crop cycle when canopy cover has declined to nil. Values of these parameters were estimated for 100 individuals of an F1 population, their parents, and five standard cultivars differing in maturity type, using data collected in six field experiments. The model successfully described differences in canopy dynamics among individual genotypes across environments. Model parameters were used to
derive several secondary variables: DP2 (duration of P2), DP3 (duration of P3), and A sum (area under the canopy cover curve reflecting the crop ’ s capacity to intercept incoming radiation). The length of P1 (i.e. t1 ) was relatively conservative, but D P2, and DP3 varied greatly. Later genotypes had higher A sum because they had longer DP2, and DP3 . Genotypic and phenotypic variance components of the F1 population were
estimated for all traits across environments and almost all of them proved significant (P<0.01). For most traits, genetic variability and heritability were high. There are opportunities, therefore, for future potato breeding programmes to exploit the genetic variability available in the F1 segregating population and to select for highly heritable traits in order to improve radiation interception efficiency.
... temperature and day length are among the major environmental factors that influence the development rate of potato and, consequently, the distribution of dm to various plant organs (Pashiardis 1987;macKerron & Jefferies 1988;Kooman & rabbinge 1996). At early growth stages, most of the dm is distributed in a fixed proportion between leaves (80%) and stems (20%) (Van Heemist 1986;Cadersa & Govinden 2000;Jenkins & mahmood 2003), and from the onset of tuber initiation, the portion of dm partitioned to the tuber will constantly be at maximum. dry matter production and allocation to the sink, the tuber, vary greatly with potato cultivars. ...
Climate, cultivar, and crop management determine the growth and dry matter (DM) production of a potato (Solanum tuberosum) crop. Drought and high temperature affect leaf area development and its persistence, and these in turn limit the photosynthetic activity of the crop and finally DM production and allocation. The objective of this experiment was to evaluate four potato cultivars for growth performance and DM partitioning to the sink by efficient use of the microclimate of the specific growing location. Four potato cultivars, namely ‘Frodo’, ‘Pentland Dell’, ‘Darius’, and ‘Shepody’, were used in the experiment. Four different harvests were undertaken during the growing season to determine DM partitioning to various parts of the plant. The results revealed that during the first harvest the percentage of leaf DM and tuber DM did not differ significantly among cultivars. The total DM accumulation for ‘Shepody’ was found to be significantly higher during the first harvest. During the second harvest, however, ‘Shepody’ and ‘Frodo’ had significantly lower DM partitioned to leaf and stem respectively, but ‘Shepody’ still had maximum total DM accumulation. Again, during the third harvest, ‘Shepody’ maintained its highest total DM accumulation and had the highest DM translocation towards tuber and the least towards leaf. ‘Shepody’ is an early maturing cultivar, and the high tuber DM during this harvest did not necessarily indicate a high final yield. This is substantiated by the final tuber harvest, where ‘Frodo’ produced a significantly higher fresh tuber yield and ‘Shepody’ yielded the least. Average leaf area index followed the same trend as the total DM accumulation, where ‘Shepody’ had significantly the highest and ‘Darius’ remained the lowest. From this, it can be concluded that ‘Frodo’ appeared to be the highest yielder, followed by ‘Pentland Dell’.
Potato (Solanum tuberosum L.) is a versatile crop given its adaptation, production capacity and utilization, and therefore valuable in many different countries. In Kenya, potato is mainly grown by smallholder farmers for food and cash. Access to quality seed of adapted and acceptable varieties was limited. This led to public–private partnerships with European seed companies working independently or with their Kenyan counterparts in introducing high-quality seed of new varieties. Some of these showed improved yield, quality and disease resistance. However, some European varieties were less adapted to the short photoperiods prevailing in Kenya than the late blight-resistant elite clones from South America, introduced by the International Potato Center (CIP). Traits that influence genotype adaptation can aid breeding cultivars or support their recommendation for certain production areas, but such traits have not been studied in detail for Kenya. This study sought to understand the adaptation of 50 contrasting genotypes from Europe, CIP and Kenya and the traits driving adaptation to four seasons and three altitudes. Genotypes showed a wide range of yields in all environments studied. The factor genotype explained most of the variance for total tuber yield (71.2%), plant height (49.3%) and area under the disease progress curve (25.1%) based on the Wald statistic, followed by season and the genotype by altitude interaction. Other traits studied hardly contributed to the understanding of the responses to the twelve testing environments. However, the largest proportions of variances for days to 50% emergence, days to maturity and canopy cover were accounted for by altitude.
