Variation In Harvest Index Research Articles

Seasonal variations in harvest index and bacoside A contents amongst accessions of Bacopa monnieri (L.) Wettst. collected from wild populations.

Bacoside A, a major active principle of Bacopa monnieri known for its cognitive effects is a mixture of saponins like bacoside A3, bacopaside II, isomer of bacopasaponin C and bacopasaponin C. Seasonal changes in biomass and bacoside A levels in fourteen accessions of B. monnieri were evaluated after maintaining these at a common site at Thapar University campus, Patiala (30°19'36.12″N and 76°24'1.08″E) for 1year. Harvestable biomass and total bacoside A contents varied significantly between the accessions and also in a particular accession during different seasons of the year. The maximum dry weight of plant (biomass 1.64g) and bacoside A levels (6.82mg/plant) were recorded in accession BM1. Harvestable biomass was highest during summer in accessions BM1 and BM7 (FW 4.2g/plant), whereas bacoside A levels were also highest during summer and in accession BM1 (6.82mg/plant). The lowest bacoside A level (0.06mg/plant) was recorded in accession BM14 during winter. Principal component analysis showed that samples of summer were positively correlated with both the components suggesting an appropriate time for the harvest.

Effect of preceding rabi crops on yield of succeeding Deshi and Tossa jute

An experiment was conducted at the Jute Research Regional Station, Kishoreganj of Bangladesh Jute Research Institute, during 2001-2002 and 2002-2003 to find out the effects of preceding crops, viz. wheat, potato, lentil, and fallow on yield of succeeding jute crops. The experiment was laid out in a randomized complete block design with four replications. The results revealed that plant height and base diameter of CVL-1 and O-9897 were not affected significantly by the preceding rabi crops. The fibre and stick yields of both the jute varieties were affected significantly. The highest fibre yield of CVL-1 (3.90 t ha-1 and 3.77 t ha-1) and O-9897 (3.51 t ha-1 and 2.93 t ha-1) was recorded when those were grown after potato and the yield was the lowest when grown after wheat and fallow land in both the years. There was no sharp variation in harvest index, which showed inconsistent between the years.Bangladesh Agron. J. 2014, 17(2): 15-19

Carbon isotope discrimination and water use efficiency in Iranian diploid, tetraploid and hexaploid wheats grown under well-watered conditions

Carbon isotope discrimination (Δ) has been proposed as physiological criterion to select C3 crops for yield and water use efficiency. The relationships between carbon isotope discrimination (Δ), water use efficiency for grain and biomass production (WUEG and WUEB, respectively) and plant and leaf traits were examined in 20 Iranian wheat genotypes including einkorn wheat (Triticum monococcum L. subsp. monococcum) accessions, durum wheat (T. turgidum L. subsp. durum (Desf.) Husn.) landraces and bread wheat (T. aestivum L. subsp. aestivum) landraces and improved cultivars, grown in pots under well-watered conditions. Carbon isotope discrimination was higher in diploid than in hexaploid and tetraploid wheats and was negatively associated with grain yield across species as well as within bread wheat. It was also positively correlated to stomatal frequency. The highest WUEG and grain yield were noted in bread wheat and the lowest in einkorn wheat. Einkorn and bread wheat had higher WUEB and biomass than durum wheat. WUEG and WUEB were significantly negatively associated to Δ across species as well as within bread and durum wheat. The variation for WUEG was mainly driven by the variation for harvest index across species and by the variation for Δ within species. The quantity of water extracted by the crop, that was closely correlated to root mass, poorly influenced WUEG. Environmental conditions and genetic variation for water use efficiency related traits appear to highly determine the relationships between WUEG and its different components (water consumed, transpiration efficiency and carbon partitioning).

Variation in harvest index of modern spring barley, oat and wheat cultivars adapted to northern growing conditions

SUMMARYIncreased harvest index (HI) has been one of the principal factors contributing to genetic yield improvements in spring barley (Hordeum vulgareL.), oat (Avena sativaL.) and wheat (Triticum aestivumL.) cultivars. Although high HI demonstrates high-yielding ability when cultivars are compared, it can also indicate challenges to yield formation when comparisons are made across differing growing conditions. The present study was designed to investigate variation in HI among modern cereal cultivars relative to that brought about by a northern environment, to assess whether HI still explains the majority of the differences in grain yield when only modern cereal cultivars are compared, and to monitor key traits contributing to HI. Stability of HI was also investigated with reference to the role of tillers. Twelve experiments (3 years, two locations, two nitrogen fertilizer regimes) were carried out in southern Finland to evaluate 12 two-row spring barley, 10 six-row barley, 10 oat and 11 wheat cultivars. In addition to HI, days to heading and maturity, length of grain filling period, grain yield, test weight and 13 traits characterizing plant stand structure were measured and analysed with principal component analysis (PCA) to detect traits associated with HI and those contributing to stability of HI. Although only modern cereals were studied, differences among cultivars were significant both in mean HI and stability of HI, and HI was associated with short plant stature in all modern cereal species. Also, single grain weight was associated with HI in all species. Differences between, but not within, species in HI were partly attributable to differences in tiller performance. Grain yield was associated closely with HI except in two-row barley. It may be possible to further increase HI of wheat, as it still was relatively low. High HI did, however, not indicate the degree of success in yield determination when environments are compared.

Physiological approaches to improving harvest index and productivity in sunflower

SUMMARY Factors associated with variation in harvest index and approaches to improve harvest index (HI) and productivity in sunflower are discussed in this article. In recent years, higher productivity in sunflower has been achieved mainly through increased crop growth rates. Besides, an improvement in harvest index also has contributed for improved productivity to a certain extent. In our study we observed that medium duration types (100 to 110 days) had high HI compared with early or long-duration varieties and we also attempted to understand the ways and means to improve HI in sunflower types with varied duration. Genotypes which had low partitioning of dry matter to stem plus thalamus had high HI. Genotypes which accumulated high biomass during post flowering stages of development also showed high HI and seed yield. In a few genotypes remobilization of photosynthates from vegetative plant parts to the seed resulted in high HI and seed yield. Among the sink characters, the number of seed per head, test weight and seed density (weight/volume) also contributed to achieving high HI values. Identification and selection of genotypes based on these criteria will increase the production further. Since large amount of biomass is still locked up in the vegetative plant parts, any practice to manipulate the mobilization of photosynthates from vegetative parts to head also improves HI and thus seed yield. In our experiment, we observed that foliar application of boron nutrient and application of growth regulators to the head improved the translocation of photosynthates to the head and thus increased the HI and seed yield.

Simulating fababean development, growth, and yield in Australia

The capability to simulate fababean (Vicia faba L.) production across the range of environments in which it is grown in Australia provides a tool for assessing agronomic and management options for the crop. This paper describes the building and testing of a model of fababean (cv. Fiord) development and growth, designed for use in the cropping systems simulator, APSIM. Parameters describing leaf area expansion, radiation interception, biomass accumulation and partitioning, root growth, water use, and nitrogen accumulation were sourced from the literature or developed from experiments conducted by the authors. In addition, parameters defining phenological development in response to temperature and photoperiod were derived from a comprehensive dataset of times to flowering and maturity.Routines for pre-flowering phenology predicted time to flowering ranging from 43 to 94 days with a root mean squared deviation (RMSD) of 4.3 days. Post-flowering development could not be satisfactorily predicted using thermal time alone; analysis of the collated data suggested that the lengths of some post-flowering phases were related to photoperiod. With incorporation of a photoperiod effect on post-flowering development, time from sowing to maturity was simulated with an R2 of 92% and an RMSD of 6.7 days.The model was tested over a diverse range of latitudinal and climatic conditions within Australia, using data from experiments in which sowing date, crop density, and water supply varied. Observed grain yield (n = 42) varied from 500 to 5600 kg/ha. In general, observed biomass and yield patterns within a growing season were reproduced well. Simulated grain yield explained 87% of the variance in observed yields (RMSD = 466 kg/ha). Apart from demonstrating the capability of the model over a wide range of growing conditions, the tests highlighted a number of areas for future improvement, including accounting for lodging, variation in harvest index under wet conditions, and accurate simulation of the response of leaf area expansion to mild levels of water deficit.

Trait diversity, heritability and genetic advance in selected germplasm lines of tef.

The genetic improvement of the Ethiopian cereal, tef, Eragrostis tef (Zucc.) Trotter, depends upon the variability in the indigenous germplasm. A bi-replicated randomized complete block field experiment was, therefore, carried out at Debre Zeit and Alem Tena in Ethiopia during the 1996 main season to study the pheno-morphic and agronomic trait diversity in 320 tef germplasm lines. All of the 17 traits assessed showed substantial (p < or = 0.001) variation among the lines. Genotypes and locations interacted significantly (p < or = 0.05) on 11 of the traits. At about 50% similarity level, the tef lines grouped into six major clusters of nine to 243 lines. Five principal components (PCs) extracted about 71% of the entire variation of the lines. About 28% of the total variance explained by the first PC was due chiefly to variation in main shoot culm length, diameters of the two basal culm internodes, panicle length and grain yield/panicle. About 16% of the whole variance explained by the second PC originated mainly from variation in the length of the first and second basal culm internodes, grain yield/plant, and peduncle length. The third PC accounting for about 12% of the entire variance resulted largely from variation in harvest index and shoot phytomass yield/plant. Across traits, the phenotypic and genotypic coefficients of variation varied in that order from about 2% for grain yield/panicle to 58% for number of fertile tillers/plant, and from less than 1% for diameters of the two basal culm internodes and grain yield/panicle to 35% for panicle length. Estimates of broad sense heritability and genetic advance (as ratio of the mean) were highest for panicle length (71%) and number of fertile tillers/plant (21%), respectively. But both of these were lowest for the second basal culm internode diameter (< 1%). Overall, the study confirmed that tef is a highly versatile crop with broad trait diversity in the germplasm, and this offers ample opportunities for improvement through breeding.

Genetic improvement of sunflower in Argentina between 1930 and 1995: Part III. Dry matter partitioning and grain composition

We compared the partitioning of dry matter and the oil and protein content in the grain of sunflower ( Helianthus annuus L.) cultivars released in Argentina between 1930 and 1995. At anthesis, the fraction of plant dry matter partitioned to leaf and head increased, whereas the fraction in the stem decreased with year of cultivar release. Improved oil yield was related to the increase in: (i) harvest index (grain mass/shoot mass) from about 0.3 to 0.5; (ii) kernel-to-grain ratio from 0.6 to 0.8; and (iii) kernel oil concentration from 58 to 70%. The duration of the period of grain growth as a fraction of season length accounted for half of the variation in harvest index. Kernel oil concentration was negatively associated with protein concentration which dropped from 23 to 13%. Further improvement in partitioning may be possible, including increase in harvest index resulting from enhanced contribution of stored assimilate to grain growth. Owing to the dramatic improvement in partitioning achieved in the last seven decades, however, further increase in yield may need to focus on increasing biomass production.

GROUNDNUT GROWTH AND DEVELOPMENT IN CONTRASTING ENVIRONMENTS. 2. HEAT UNIT ACCUMULATION AND PHOTO-THERMAL EFFECTS ON HARVEST INDEX

When the same cultivars of groundnuts (Arachis hypogaea) were grown under a wide range of environmental conditions, temperature and irradiance played a major role in determining crop duration and partitioning of dry matter to pods, the latter assessed by harvest index. Utilizing published data for the Virginia groundnut cultivar Early Bunch under non-limiting conditions, we show that accumulation of thermal time using three cardinal temperatures (Tb=9 °C, To=29 °C and Tm=39 °C) has considerable potential for predicting crop maturity. In sixteen sowings ranging from the wet tropics in Indonesia to the elevated subtropics in Australia, harvest date for Early Bunch corresponded to the accumulation of 1808 (±23) degree-days after sowing. In all sowings except one in the semi-arid tropics, this value of thermal time was within eight calendar days of actual harvest maturity. Harvest index varied greatly with both location and sowing date, ranging from 0.31 (Indonesia) to 0.58 (subtropical Australia). Using total short-wave solar radiation incident during the growing season and calculated values of thermal time, the growing season for each sowing in each location was described in terms of a photo-thermal quotient (PTQ, MJ m−2 degree-day−1). Values for PTQ ranged from 0.99 (Indonesia) to 2.11 (subtropical Australia). Variation in harvest index could be explained largely by a curvilinear function of PTQ (R2=0.98), provided data were not confounded by the effects of photoperiod. In the semi-arid tropical environment, decreases in photoperiod associated with delayed sowing were the dominant factor controlling harvest index.

Effects of climate on different potato genotypes 1. Radiation interception, total and tuber dry matter production

In 11 field trials in Rwanda, Tunisia and The Netherlands, the total dry matter production and tuber dry matter production of eight potato cultivars were analysed in terms of radiation interception and radiation use efficiency. The variation in length of the growing season was the most important factor explaining the differences in both total and tuber dry matter production among cultivars and sites. Radiation interception was the most important factor because the radiation-use efficiency was negatively correlated with radiation intensity and the variation in harvest index was of minor importance. Variation in length of the growing season among sites was related to daylength and temperature, in that shorter days at emergence and higher temperatures throughout the season resulted in a shorter growth cycle. The extent of these effects differed among cultivars, and it was concluded that climatic effects on tuber dry matter production could be attributed to the effects of temperature and daylength on the length of the growth cycle.

Variation in harvest index of maize (Zea mays) and common bean (Phaseolus vulgaris) grown in a marginal rainfall area of Kenya

SUMMARYMaize (Zea mays L.) and common bean (Phaseolus vulgaris L.) were grown in five seasons, beginning in the long rains 1990 and ending in the short rains 1992, at Kiboko, Kenya under a range of different management conditions (N fertilization, irrigation, population density and intercropping). Seed weight was plotted against total dry weight to determine harvest index for both crops. For bean the intercept of this relationship for each experiment, with one exception, was not significantly different from zero, so that the slopes of the regressions were the harvest indices. Harvest indices for bean varied more between seasons (0·38–00·85) than from the effects of management practices (00·53–0·71). Over all seasons and treatments, the index for bean did not vary systematically with crop weight, and averaged 0·50. By contrast, a similar analysis for maize over all seasons and treatments, showed that the harvest index varied with crop dry weight, approaching an asymptotic value as dry weight increased. The regression intercepts for the different experiments were significantly different from each other, and in three cases differed significantly from zero. Therefore, although the slopes for the different experiments were parallel, they did not always represent the harvest index.

Comparative productivity of maize, sorghum and pearl millet in a semi-arid tropical environment I. Yield potential

The comparative productivity of high-yielding F 1-hybrids of maize, sorghum and pearl millet grown under fully irrigated and high-fertility conditions was examined at three sowing dates in semi-arid tropical Australia. The study was undertaken to determine the yield potential of these species, to allow assessment of yield limitations due to environmental and management factors, and to evaluate the possibility for yield improvement for cereals in the semi-arid tropics. Variation in yield was analysed in terms of the amount of incident radiation intercepted by the crops, its efficiency of use in dry-matter production, and the proportion of dry-matter partitioned to grain. The varying radiation and temperature regimes across sowing dates affected biomass at maturity in maize and millet, but not in sorghum. Variation in biomass across sowing dates was associated more with differences in the amount of radiation intercepted than in radiation-use efficiency. In contrast, grain-yield was relatively stable across sowing dates in maize, but it varied with sowing date in sorghum and millet. Here, differences in grain-yield were related more to variation in harvest index. Overall, variation in grain-yield across sowing dates within species was small relative to that among species. Average grain-yields over the three sowing dates were 9.2 t ha −1 for maize, 5.6 t ha −1 for sorghum and 2.9 t ha −1 for millet. High yield was associated with high biomass production both at maturity and during grain-filling, high harvest index, and an increase in stover weight during grain-filling. High biomass-accumulation was associated with long growth-duration, especially the duration of grain-filling and thus high cumulative radiation interception, and with high radiation-use efficiency.

The Physiological Basis for Yield Differences between Four Genotypes of Groundnut (Arachis Hypogaea) in Response to Drought. I. Dry Matter Production and Water Use

SUMMARYFour genotypes of groundnut grown with limited irrigation in a medium depth Alfisol in Central India transpired similar total amounts of water (220–226 mm) over the season, but produced different amounts of shoot dry matter (390–490 g m−2). The extraction front of Kadiri 3 moved most rapidly down the soil profile which may have enabled it to maintain the fastest rates of transpiration when soil water depletion was greatest. Tap root extension rates of Kadiri 3 in the first 32 days after sowing were also the fastest. NC Ac 17090 was more efficient than the other genotypes in extracting water immediately after irrigation from the upper 40 cm of the soil, but this had little value in determining the pattern of water availability in this experiment. Differences in the water extraction characteristics of these genotypes explain little of the variation in dry matter:water ratio, and do not account for the major variation in harvest index associated with drought.

Effect of nitrogen supply on the comparative productivity of maize and sorghum in a semi-arid tropical environment III. Grain yield and nitrogen accumulation

Differences in grain yield and grain nitrogen content due to variable N supply in maize and sorghum, grown under irrigation in the semi-arid tropics, were associated with differences in their rates of accumulation and in the extent of mobilization of pre-anthesis dry matter and N. Increases in harvest index, nitrogen harvest index, and grain size during grain-filling were essentially linear, and the rates were constant under variable N supply. Differences in harvest index at maturity at different levels of applied N were small relative to differences in biomass and grain yield, and differences in grain size were small relative to differences in grain number. In effect, variation in harvest index and grain size at maturity was associated with variation in the length of the effective grain-filling period. Nitrogen supply had a greater effect on the effective duration of grain-filling in maize than in sorghum. Maximum grain yields at high levels of N uptake were greater in maize (10.0 t ha −1 at 15.5% moisture) than in sorghum (7.2 t ha −1 at 14% moisture). These differences were related to differences in biomass production, rate of increase in harvest index and the effective duration of grain-filling. The rate of increase in harvest index was greater, but biomass production was less and the duration of grain-filling was shorter, in sorghum than in maize.

Crop responses to carbon dioxide doubling: a literature survey

Atmospheric carbon dioxide (CO 2) concentration will probably double by the middle of the next century. Since this is widely expected to increase crop yields, the Department of Energy has established a research program to gather data on the effects of CO 2 on plants and to develop models that can be used to predict how plants will behave in a future high-CO 2 world. This paper identifies strengths and weaknesses in the knowledge base for modelling plant responses to CO 2. It is based on an extensive tabulation of published information on responses of ten leading crop species to elevated CO 2. The response variables selected for examination were: (a) net carbon exchange rate, (b) net assimilation rate, (c) biomass accumulation, (d) root:shoot ratio, (e) harvest index, (f) conductance, (g) transpiration rate and (h) yield. The results were expressed as a predicted percentage change of the variable in response to a doubled CO 2 concentration. In most instances, a linear model was used to fit the response data. Overall, the net CO 2 exchange rate of crops increased 52% on first exposure to a doubled CO 2 concentration, but was only 29% higher after the plants had acclimatized to the new concentration. For net assimilation rate, the increases were smaller, but fell with time in a similar way. The C 4 crops responded very much less than C 3 crops. The responses of biomass accumulation and yield were similar to that for carbon fixation rate. Yield increased on average 41% for a doubling of CO 2 concentration. The variation in harvest index was small and erratic except for soybean, where it decreased with a doubling of CO 2 concentration. Conductance and transpiration were both inversely related to CO 2 concentration. Transpiration decreased 23% on average for a doubling of CO 2. Crop responses to CO 2 during water stress were variable probably because high CO 2 both increased leaf area (which increases water use) and reduced stomatal conductance (which decreases water use). However, low nutrient concentrations limited the responses of most crops to CO 2. The absolute increase in photosynthetic rate in response to high CO 2 concentration was always greater in high light than in low light, but this was not necessarily true of the relative increase. In all except one study, responses to CO 2 were larger at high temperature than at low. Most of these studies were done in high light intensity. In low light intensity, the effect of temperature on the CO 2 response was smaller.

Increasing grain yield of oats by independent culling for harvest index and vegetative growth index or unit straw weight

Most variation in grain yield of oats is due to variation in harvest index and vegetative growth index, but the latter traits are negatively associated. Therefore we used independent culling levels to select oat genotypes with high levels of vigor traits and a desirable level of harvest index in an attempts to maximize grain yield. Harvest index and vegetative growth index or harvest index and unit straw weight were selected at various culling levels. Intensive selection for harvest index resulted in high harvest index but no grain yield improvement, because the selected lines had poor vigor. Intensive selection for vegetative growth index or unit straw weight resulted in high biomass but low harvest index.

Relationships between seed yield and yield components in narbon bean (Vicia narbonensis L.) by path analysis

Results of correlation analysis indicated that seed yield in narbon bean (Vicia narbonensis L.) was correlated positively with harvest index, biological yield, weight, number of seed and number of pod per plant and also plant height and number of plant per m2. Path coefficient analyses revealed that harvest index and biological yield had higher positive direct effects on seed yield than other variables. Stepwise multiple regression analysis showed that 95.1% of total variation in seed yield could be explained by the variation in harvest index, biological yield and plant height. Results suggest that harvest index and biological yield are primary selection criteria for improving seed yield in narbon bean. &#x0D;