Changes In Yield Components Research Articles

An early-morning flowering trait in rice can enhance grain yield under heat stress field conditions at flowering stage

An early-morning flowering (EMF) trait is supposed to be effective in enhancing grain yield due to mitigation of heat-induced spikelet sterility at flowering in rice. This study evaluated (i) phenotypic differences between a near-isogenic line carrying a QTL for EMF trait (designated as IR64 +qEMF3) and a recurrent parent, IR64, under wide variation in climates and (ii) whether the EMF trait can enhance grain yield under heat stress at flowering. IR64 +qEMF3 had significant earlier flower opening time (FOT) in diverse environmental conditions including temperate, subtropical, and tropical regions. FOT differentially responded to maximum and minimum air temperatures between genotypes. Under non-heat stress temperatures at flowering, IR64 +qEMF3 had similar grain yield to IR64 with minimal changes in yield components. Seven field trials in heat-vulnerable regions of Myanmar for multiple years showed that higher percentage of grain set contributed to the significantly higher grain yield in IR64 +qEMF3 when plants were exposed to daily maximum air temperatures around 36.1 °C or higher. Lower spikelet sterility in IR64 +qEMF3 was attributed to the earlier FOT during cooler early morning hours. This is the first field study that clearly demonstrates the enhancement of grain yield due to EMF trait under diverse heat stress field conditions at flowering.

Changes in Yield Components of Paddy Rice Due to Short-Term Flooding at the Panicle Developmental Stage and the Ripening Stage

Changes in Yield Components of Paddy Rice Due to Short-Term Flooding at the Panicle Developmental Stage and the Ripening Stage

Changes in yield components, morphological, physiological and fruit quality traits in processing tomato cultivated in Italy since the 1930’s

Yield of processing tomato (Solanum lycopersicum L.) increased (∼ 50%) in Italy since the 1930’s. The aim of this work was to assess the changes in yield components associated with morphological, physiological and fruit quality traits in processing tomato cultivars cropped in Italy from the mid-1930s until nowadays, introduced by breeding in six representative cultivars. Marketable yield showed an increase of 0.6% per year of release since the 1930’s. The highest marketable yield was obtained in modern cultivars due to a higher harvest index, fruit number and the ratio between ripe fruit and total fruit in comparison with the old ones. However, no single trait drove the highest marketable yield in modern cultivars. In fact, both morphological (smaller plant height and leaf area index) and physiological (accelerated plant senescence, higher leaf nitrogen status, and lower potential plant water and chlorophyll contents) traits contributed to increase marketable yield in modern cultivars. Moreover, total plant dry weight (shoot + fruit) of a single plant decreased, whereas its total fruit fresh weight and fruit dry matter content were stable and not correlated with the year of release, thus suggesting that a higher sink strength and homogeneity of fruit ripening were also involved in the highest marketable yield showed by modern cultivars. A great effort of breeders was done in the improvement of important fruit quality traits required by Italian canning industries. Fruit colour and Brix yield were positively correlated with the year of release, while viscosity and total carotenoids were negatively correlated with the year of release. However, no improvement was achieved for important traits such as soluble solids content, fruit dry weight and total fruit yield, which instead should be considered in the future breeding programmes, to improve both yield and quality of processing tomato.

Plant spatial arrangement affects grain production from branches and stem of soybean cultivars

ABSTRACT Phenotypic plasticity is the ability of plants to undergo changes in morphology and yield components to adapt themselves to distinct environmental conditions. The knowledge on the changes in yield components of branches and stems at varied plant spatial arrangements needs to be updated due to recent changes in soybean production system. Thus, this study aimed to evaluate the yield components of branches and stems, as well as to assess the share of these plant parts in the total grain yield of soybean cultivars with indeterminate growth type, under different spatial arrangements. The experiment was conducted during the growing seasons of 2013/2014 and 2014/2015, under a randomized complete-block design and in a4 × 3 × 2 factorial scheme with three replications. Treatments consisted of four row spacing patterns (narrow rows, twin rows, traditional row spacing, and crossed rows), three seeding rates (150, 300, and 450 thousand viable seeds∙ha–1), and two cultivars (BMX Potencia RR and BRS 359 RR). Narrow rows reduce pods and grains production in branches in relation to the traditional row spacing. The number of grains per pod of stem and of branches is not altered by the changes in plant arrangement. The increase in seeding rate reduces the number of pods per plant of branches in greater magnitude than that of stems. The rise in seeding rate results in larger thousand-grain mass both of branches and of stems, but varies with the growing season.

SELECTION RESPONSE FOR INCREASED GRAIN YIELD IN TWO HIGH OIL MAIZE SYNTHETICS

Selection for increased oil level in maize showed the increase was associated with decrease in starch concentration, kernel weight, and grain yield. The study was conducted with the objectives: (1) to evaluate response to six cycles for increased grain yield in the high oil maize Alexho Elite (AE: 60-90 g kg-1 oil concentration) and Ultra High Oil (UHO: 100-140 g kg-1 oil concentration) using inbred tester B73; (2) to measure responses to selection for increased grain yield with changes in yield components; and (3) to determine a suitable tester. Previously the two synthetics had been selected for oil concentration. After six cycles, the six genotypes i.e. AE C0, AE C3, AE C6, UHO C0, UHO C3, and UHO C6 were testcrossed to B73, LH185, and LH202 inbreds (40 g kg-1 oil concentration) to a total of 18 testcrosses. Two field experiments were used to evaluate selection in AE and UHO testcrosses. The study showed selection using inbred tester B73 in AE and UHO was effective in increasing grain yield of AE testcrosses without changing (i.e. decreasing) oil and protein concentrations. AE testcrosses produced higher grain yield and greater selection response for grain yield than UHO testcrosses. LH185 was best for grain yield in AE and UHO testcrosses. Increase in grain yield in most of the testcrosses was associated with increases in starch concentration, kernel weight, kernel number, and grain weight.

SELECTION RESPONSE FOR INCREASED GRAIN YIELD IN TWO HIGH OIL MAIZE SYNTHETICS

Selection for increased oil level in maize showed the increase was associated with decrease in starch concentration, kernel weight, and grain yield. The study was conducted with the objectives: (1) to evaluate response to six cycles for increased grain yield in the high oil maize Alexho Elite (AE: 60-90 g kg-1 oil concentration) and Ultra High Oil (UHO: 100-140 g kg-1 oil concentration) using inbred tester B73; (2) to measure responses to selection for increased grain yield with changes in yield components; and (3) to determine a suitable tester. Previously the two synthetics had been selected for oil concentration. After six cycles, the six genotypes i.e. AE C0, AE C3, AE C6, UHO C0, UHO C3, and UHO C6 were testcrossed to B73, LH185, and LH202 inbreds (40 g kg-1 oil concentration) to a total of 18 testcrosses. Two field experiments were used to evaluate selection in AE and UHO testcrosses. The study showed selection using inbred tester B73 in AE and UHO was effective in increasing grain yield of AE testcrosses without changing (i.e. decreasing) oil and protein concentrations. AE testcrosses produced higher grain yield and greater selection response for grain yield than UHO testcrosses. LH185 was best for grain yield in AE and UHO testcrosses. Increase in grain yield in most of the testcrosses was associated with increases in starch concentration, kernel weight, kernel number, and grain weight.

Effect of density, cultivar and irrigation on spring sown monocrops and intercrops of wheat (Triticum aestivum L.) and faba beans (Vicia faba L.)

Spring-sown intercrops of wheat (Triticum aestivum L.) and faba beans (Vicia faba L.) were grown in three experiments at the University of Reading, UK. One wheat cultivar, Axona, and one (experiment 1) or two bean cultivars (experiments 2 and 3) Scirocco and Maris Bead, were grown as sole crops and intercrops at 50%, 75% and 100% recommended density. Experiments were rainfed but irrigation was an additional treatment in experiment 3. Biomass and seed yields of both wheat and faba beans were greater when monocropped than when intercropped. There was no evidence that radiation use efficiency (RUE) of intercrops was significantly different from sole crops. In all intercrops there was no significant effect of density on biomass, RUE or seed yield, though there were compensating changes in yield components. Seed yields of Maris Bead were significantly greater than Scirocco in experiment 3 but not experiment 2. There was no significant effect of irrigation on RUE or on wheat biomass and seed yield, but there was a trend for irrigation to increase faba bean biomass (P=0.07) and seed yield (P=0.06). With later sowing in experiments 2 and 3, time to harvest was shorter and wheat and bean biomass, seed yield and RUE were reduced. All land equivalent ratio (LER) values for both biomass (maximum 1.23) and seed yield (maximum 1.44) were greater than 1, with one exception in experiment 3, indicating that intercrops of wheat and faba beans make more effective use of land than equivalent sole crops. Partial LERs for faba beans were always lower than those of wheat. The tendency was for highest LERs to occur at 75% recommended density.

Quantifying three-decade changes of single rice cultivars in China using crop modeling

This paper combines the analysis of rice growth data with crop modeling to quantify the changes in single rice cultivars over three decades from 1981 to 2009 at four sites in China. Crop data include timing of main developmental stages, aboveground biomass, grain yield, 1000-grain weight, grain number per spike, percentage filled grains, and plant density. The APSIM-Oryza model was used to quantify the rice cultivar changes and their impact on growth and yield. The results showed that cultivar changes could be explained by the changes in rice physiology captured in APSIM-Oryza and changes in yield components. Cultivar changes mainly involved: (1) the increase in actual thermal time requirements during the growing period as a result of reduced development rates and photoperiod sensitivity and extended grain filling period, which compensated the negative impact of warming to shorten growing period and stabilized or increased aboveground biomass and (2) the increase in grain numbers and harvest index as a result of the dwarfing and improved growth. Once these changes could be captured in the parameterization of model, APSIM-Oryza could explain 61.7% of the variation in observed aboveground biomass and 55.1% of the variation in grain yield. This demonstrates that crop modeling is an efficient means to study the impact of environmental and cultivar changes on crop productivity in the future. It also highlights the needs to quantify the physiological changes in new cultivars by combining field observations and crop modeling in future research.

Productivity of a doubled haploid winter wheat population under heat stress

Abstract Breeding of new winter wheat cultivars with good heat tolerance requires better understanding of the genetic background of heat tolerance. In the present work the effect of heat stress on the 6th day after heading was investigated in a doubled haploid (DH) population arising from a cross between heat-sensitive (Plainsman V) and heat-tolerant (Mv Magma) cultivars. Averaged over the population, heat stress was found to result in a significant reduction in biomass, grain yield and grain number per plant, and in thousand-kernel weight (TKW) and harvest index. High temperature had the greatest effect on the grain yield, with a drop of 36.2% compared with the control. This could be attributed jointly to significant reductions in the TKW of the main ear and in the grain number of the side tillers. The relationship between the yield parameters was confirmed by the positive correlations obtained for the lines in the population. The diverse levels of heat tolerance in the different lines were confirmed by the significant differences in the reduction in the chlorophyll content (SPAD index) of the flag-leaves and in yield parameters. The changes in yield components in stress condition, however, can be still the most effective tools for heat stress evaluation.

Yield formation strategies of durum wheat landraces with distinct pattern of dispersal within the Mediterranean basin I: Yield components

This study was undertaken to ascertain whether the pattern of dispersal of durum wheat within the Mediterranean basin is associated with variation in phenology and yield formation strategies. A set of 52 durum wheat landraces, previously genetically characterized as been dispersed by the north or south of the Mediterranean region, were grown in three rainfed sites in a dry-temperate region (Lleida, NE Spain), and crop phenology, yield and yield components were determined. Northern genotypes had a larger number of stems per unit area, but a lower percentage of fertile tillers and fewer grains per spike than southern landraces. Grain yield for the northern dispersal group was mainly related to variations in thousand-kernel weight, while the number of spikes per m 2 was the component most highly correlated with yield among southern genotypes. These contrasting yield formation strategies are probably a consequence of the different climates prevalent in the zones of adaptation, and likely conferred adaptive advantages to the genotypes of one or the other group. Our results suggest that gradual changes in yield components occurred during the movement of durum wheat from east to west through the north side of the Mediterranean basin. According to our results, the weight of grains and the number of spikes per unit area may be selection criteria to improve adaptation for the northern and the southern parts of the Mediterranean basin, respectively.

Influence of Phosphorus and Potassium on Alfalfa Yield and Yield Components

Phosphorus and K fertilization increases alfalfa (Medicago sativa L.) yield and stand persistence, but the changes in yield components as affected by P and K fertility level are not known. Our hypothesis is that P and (or) K fertilization will increase one or more alfalfa yield components, and those component responses may change with stand age. The objectives of this field study were to determine the impact of P and K fertilization on alfalfa forage yield and yield components during the initial 3 yr after establishment. Treatments were the factorial combinations of four P rates (0, 25, 50, and 75 kg P ha−1) and five K rates (0, 100, 200, 300, and 400 kg K ha−1) arranged in a randomized complete block design with four replications. Forage harvests occurred four times annually, and yield, mass shoot−1, and shoots area−1 were determined. Plant populations were determined in early December and late May each year. Incremental additions of P and K increased alfalfa yield in each year. Potassium fertilization did not influence plant population, while robust P-responsive alfalfa plants apparently crowded out smaller, less vigorous plants thus decreasing plants m−2 Stand assessments based on shoot counts, or aboveground plant counts may not accurately indicate alfalfa yield potential. Shoots plant−1 was not affected by application of either nutrient, while shoots m−2 generally declined with increased P and K fertilization. Improved forage yield of P- and K-fertilized plots was consistently associated with greater mass shoot−1 Because fertilizer-responsiveness is closely associated with greater mass shoot−1, cultivars possessing this trait may be relatively more productive under well-fertilized conditions.

Association between adaptation type and changes in the yield components of barley (Hordeum vulgare L.) varieties influenced by vernalization and daylength

Changes in the yield components of 35 barley varieties, which formed eight adaptation groups, were studied as a function of daylength and vernalization treatment under controlled conditions. Changes in the daylength had a significant effect on the yield components in the majority of adaptation groups, though the extent and direction of these changes varied. In spring barley groups there was an increase in plant height, number of reproductive tillers and in the thousand kernel weight, while the number of spikelets, the grain number of the main spike and the grain yield decreased as the daylength became shorter. Among the winter barley varieties, changes in daylength had a significant influence on yield components only in those groups, which were sensitive to long and/or short days. The groups sensitive to long days produced higher grain yields under long-day conditions than the insensitive group. Under short days the grain yield of groups sensitive to short days declined to a greater extent than that of the insensitive group. The effect of vernalization on the yield components depended strongly on the vernalization requirements of winter barleys. Most of the yield components of winter barleys with the highest vernalization responses were significantly influenced, with the exception of the grain number in the main spike. Changes in yield components showed specific patterns between these eight groups well corresponding to the different adaptation types determined by their heading date characteristics.

Nine cycles of mass selection for increasing oil content in two maize (Zea mays L.) synthetics

The objectives of this study were to estimate changes in oil content, grain yield, percentage of broken plants and changes in yield components in the maize populations DS7u and YuSSSu. As estimations were performed at C0 and C9 for both populations, it was possible to observe changes occurring following long-term mass selection for high oil content. The synthetic population DS7u population was developed by recombination of 29 inbred lines of Yugoslav, Canadian and US origin. The synthetic population YuSSSu population is an Iowa Stiff Stalk Synthetic - BSS(R)C5. Progenies were derived according to the North Carolina Design II. Results indicated that nine cycles of selection led to statistically significant increase in oil content and statistically significant decrease for grain yield in both populations. Estimates of additive and dominance variances for grain oil content were highly significant in C0 and C9 of the population DS7u population. Dominance variance showed significance in the initial cycle of the population YuSSSu population, but it was not detected in the course of nine cycles of mass selection. Additive and dominance variances for grain yield were highly significant in both initial populations. Loss of significance did not result from selection, while the proportion of dominance vs. additive variance became greater. High narrow-sense heritability was detected for grain yield, oil content, moisture content, and cob percent in the initial cycles of both populations. Mass selection resulted in increased heritability for oil content and cob percent in the DS7u population and increased heritability for percentage of broken plants in the YuSSSu population. The strongest additive correlation between oil content and other traits was detected for grain moisture (r a = 0.90*) in the C9 of the DS7u population.

Assessment of Western Canadian Barleys of Historical Interest: I. Yield and Agronomic Traits

Changes in yield components and agronomic traits may contribute to historical yield advances. The purpose of this study was to determine the yield advances that have been made in spring barley (Hordeum vulgare L.) cultivars released in western Canada from 1910 to 1987 and to evaluate the contribution of yield components and agronomic traits to yield advancement. An important goal was to determine the value of individual traits to an ideotype of barley for the western Canadian prairies. Twenty cultivars of both six‐ and two‐rowed types were tested at Botha, Lacombe and Olds, Alberta, Canada, in 1989 and 1990. Grain yields increased by 12.7 to 41.4 kg ha−1 yr−1 with the greater responses being in the more favourable environments. This increase in grain yield was associated with increased harvest indices of 0.08 to 0.17% per year. Lodging decreased by 0.01 to 0.05 points per year (0–10 scale). Seed protein content decreased by 0.01 to 0.02 g kg−1 yr−1. Test weights responded positively to year of release in the 1990 tests at Botha and Olds. Spike number per square meter and net blotch severity were associated with year of release in some location‐years but response was limited. Vegetative biomass, plant stand establishment, kernel weight, kernels per spike, and response to scald had not changed over years. Increases in grain yield associated with increased harvest indices and reduced lodging have been made in western Canadian barley cultivars. Further efforts to increase vegetative yield, kernel weight and kernel number per spike, while maintaining harvest indices and lodging resistance would appear warranted.

Yield Component Responses Associated with Increased Groat Yield after Recurrent Selection in Oat

Analysis of yield into components may provide information for devising efficient selection strategies for improving yield or traits correlated with yield in cereal crops. Our objective was to analyze changes in yield components associated with increased groat yields observed within three S1‐recurrent selection programs for high protein yield (grain yield × groat‐protein concentration) in oat (Avena sativa L.). Selection emphasized high protein yield per se (HGP), with no restrictions in grain yield or groat‐protein concentration; high protein yield due only to high grain (HG) yield; and high protein yield due to both high groat‐protein concentration and high grain yield (HP). Responses of yield components to these selection criteria were evaluated by growing 30 to 60 random S0‐derived lines from each selection cycle (C) in a hill plot experiment at two Iowa locations in 1989. Above ground biomass increased 7%, vegetative growth index (vegetative yield/number of days to heading) increased 9%, and groat index (groat yield/biomass) increased 8% from C0 to C5 in HGP. Changes in biomass, vegetative growth index, and groat index from C0 to C5 of HG were similar to those of HGP in direction, but were greater in magnitude (15,13, and 17% increases, respectively). Biomass increased by 5% from C0 to C5 in HP, but vegetative growth index and groat index did not change significantly. Seed number per plot increased in HGP by 16.6%, in HG by 28.2%, and in HP by 11.4%. Groat weight remained unchanged in all three lines of descent. Thus, the increased groat yields in all lines of descent were due first to greater biomass and second to high seed numbers.

Radiation-use efficiency in relation to row spacing for late-planted soybean

Greater soybean [ Glycine max (L.) Merr.] yield can be achieved at late planting dates by using row spacings narrower than conventional wide rows (76 to 100 cm). Objectives were to determine the relative yield performances of 100−, 50−, and 25-cm row spacings in late-planted soybean and to relate yield differences to changes in yield components, several growth dynamic parameters, and radiation interception. Field studies were conducted at Baton Rouge, LA (30°N Lat.) from 1989 through 1991 at a late planting date with ‘Centennial’ soybean (Maturity Group VI) planted on 100−, 50−, and 25-cm row spacings. The test was conducted on a silty clay soil. Highest yield occurred with 50-cm row width. Yield in the 25− vs. 50-cm rows was less, even though light interception (LI) patterns were similar. Growth dynamic analysis revealed that radiation-use efficiency (RUE) during the first half of the seed filling period was significantly lower in 25− vs. 50− or 100-cm rows. Reduced RUE in 25-cm row spacing was related to reduced pod number associated with lower crop growth rate (CGR) from pod initiation to 10 days after seed initiation. Results indicate that factors other than optimal LI (95%) affect yield responses to row width.

Influence of Planting Date and Seeding Rate on Winter Wheat Grain Yield and Yield Components

Winter wheat (Triticum aestivum L.) is commonly seeded over a 60-d period in the Midwest depending on crop rotation options, weather, and other farm operations. This study was conducted to determine whether winter wheat seeding rates should be altered depending on planting date and cultivar. Seeding date and planting rate responses of the cultivars, Merrimac and Cardinal, were evaluated at the University of Wisconsin Arlington Research Station during the 1988 to 1991 growing seasons. Eight planting dates ranged from 24 August to 3 November and seeding rates were 14, 28, 42, and 56 seeds/sq ft. Grain yield and yield components were influenced by all variables and specific interactions. Heads per square feet and kernel weight, two primary yield components, decreased as seeding was delayed after 12 September. Maximum grain yield occurred when planting Cardinal on 3 September using 28 seeds/sq ft. Delaying Cardinal planting to late September required a seeding rate of 42 to 56 seeds/sq ft to maximize yield. When planted in September and early October, Cardinal had higher yields than Merrimac due to heavier kernel weight. Changes in yield components allowed plants to adjust to varying conditions as planting was delayed. As grain yield decreased with a planting delay into October, kernel weight and heads per square feet continued to decrease for both cultivars. When planting was delayed past 3 October in 2 of the 4 yr, Merrimac had greater kernel weight, which translated into higher Merrimac grain yields than Cardinal. Grain yields of wheat planted in late October decreased due to yield component response to environment and to stage of plant development when growth ceased. These results can be used to improve establishment and yield of winter wheat, especially when planting at dates that are not always optimum. Research Question Producers aiming for maximum winter wheat grain yields need to begin with successful establishment of the wheat crop in the fall. Optimum planting date and seeding rate are necessary if one wants to attain high yields. This study compared planting date and seeding rate of two cultivars of varying winterhardiness to determine which combination produced maximum grain yields. Literature Summary Previous planting date research has determined that early seeding allows better stand establishment leading to greater yields. Research in Canada established that once planting date is determined, maximum yield for that date will be attained if yield components are managed by adjusting the seeding rate. Cultivars with different degrees of winterhardiness may influence optimum planting date and seeding rate. No published literature was found that examined the interaction of cultivars with planting date and seeding rate for the soft red winter wheat growing region of the Midwest. Study Description This study was conducted for 4 yr, 1988 to 1991, at Arlington, WI, using wheat management practices to maximize grain yield. Date: Eight planting dates in 10-d increments from late August through early November Cultivars: Merrimac-very winterhardy Cardinal-moderately winterhardy Rates: 14, 28, 42, and 56 weeds sq ft Applied Question Are optimum winter wheat seeding rates influenced by planting date and cultivar? Cardinal produced higher yields than Merrimac at all seeding rates when planted prior to 1 October when averaged over all 4 yr of our study (Fig. 1). While cultivars frequently responded differently to planting dates and seeding rates we did not find significant three-way interactions for grain yield. As planting was delayed into October, Merrimac grain yield decreased less rapidly than Cardinal. Merrimac planted in mid-to-late October also provided more consistent yields than Cardinal. We found maximum grain yields could be obtained by seeding Cardinal at 28 to 56 seeds/sq ft up to the third week in September. Growers could save seed costs, however, by using 28 to 42 seeds/sq ft, since the higher rate offered no advantage with early planting dates. When planting date is delayed past 1 October, yields are consistently higher at seeding rates of 42 to 56 seeds/sq ft for both cultivars; however, growers could reduce their risk of crop failure by switching to a more winterhardy cultivar, such as Merrimac. Profitability of winter wheat in the Midwest was the primary objective of our work. We recommend planting higher yielding, less winterhardy cultivars, using lower seeding rates early in the fall for maximum yields. If planting is delayed into October, we recommend that growers switch to more winterhardy cultivars and increase seeding rates. Figure 1Open in figure viewerPowerPoint Effect of planting date and seeding rate on yield of a. Merrimac and b. Cardinal SRWW, averaged over 4 yr, 1988–1991.

Effects of a short-term p-hydroxybenzoic acid application on grain yield and yield components in different tiller categories of spring barley

The aim of these experiments was to evaluate how thresholds for phytotoxic substances obtained in seedling bioassays relate to yield losses or changes in yield components of mature barley crops after a short-term exposure to p-hydroxybenzoic acid. Under laboratory conditions a treatment with 1.81 mM p-hydroxybenzoic acid significantly reduced the radicle length of barley, whereas coleoptile elongation was less sensitive. The inhibition of the radicle length and coleoptile elongation was greater if the pH of the test solution was not buffered at pH 5.5. In a glasshouse trial the effect of p-hydroxybenzoic acid on the radicle and coleoptile elongation of spring barley was compared with the yield response after a three day exposure either during germination or at the double ridge stage of apex development. Applications of 0.72 mM, 1.44 mM and 3.62 mM p-hydroxybenzoic acid averaged over the treatments during germination or at the double ridge stage of development caused a yield reduction in the single ear weight of 5%, 13% and 19% in comparison with the control, respectively. The higher tiller categories in general showed a greater sensitivity towards an application of p-hydroxybenzoic acid and, therefore, could not compensate for the yield decrease of the main stem tiller. A single application of p-hydroxybenzoic acid either at germination or at the double ridge stage may cause yield losses, as reported from no-till systems or cereal monocultures. The data have implications for the interpretation of seedlings bioassays in allelopathic research and their applicability in estimating yield losses caused by phytotoxic substances. ei]Section editor: R Merckx

Fruiting Activity, Growth and Yield of Oil Palm. I. Effects of Fruit Removal

SummaryThe relation between current yield and future yield components in the oil palm (Elaeis guineensis Jacq.) was investigated by removing a proportion of inflorescences before anthesis. This disbudding caused mean fruit bunch weight to increase by over 60%, with corresponding increases in the components of bunch weight. The total number of inflorescences produced increased by 10%, the sex ratio increased from 72 to 91% females, and inflorescence abortion and bunch failure rates were halved. As a result, the number of bunches harvested was reduced by less than the level of disbudding, and removal of 75% of inflorescences only reduced yield by 42%. Disbudded palms also grew more vigorously. The time intervals between a change in the level of fruiting activity and the resulting changes in yield components were determined by recording the yield components during the period after disbudding was stopped.

Yield and Biochemical Response of Sugarbeet to Benomyl1

AbstractTwo field studies were conducted to determine the effects of the systemic fungicide benomyl [methyl 1‐(butylcarbamoyl)‐2‐benzimidazolecarbamate] applied at protectant levels to the foliage of sugarbeet (Beta vulgaris L.), on yield components, recoverable sucrose, and six root extract chemical constituents. In the initial study (1980 and 1981), six benomyl applications (271 g a.i. ha−1, at 2‐week intervals beginning in late June) to disease‐free sugarbeets significantly increased yield components and decreased amino N, total N, and betaine. The objective of the second study (1982–1984) was to determine the effect of timing and number of benomyl applications during the growing season. In each year, five benomyl treatment regimes, ranging from single applications to six sequential applications, were evaluated for their effects. All non‐sucrose chemical component means across cultivars decreased as a result of benomyl treatment. These reductions were consistent and statistically significant for total N, amino N, and betaine. Means for sucrose, purity, and root weight increased in response to benomyl in 1980 and 1981 although not significantly so for sucrose. There was a significant year‐effect on changes in yield components and lack of consistency for any given treatment on extract chemical composition. Thus, these data did not point to a specific physiological basis for the observed effects.