Effects of maturity genes E2 and E3 on yield formation in soybean cultivar Enrei in warm region,Fukuyama in Japan

ABSTRACT

Understanding how maturity genes affect soybean yield formation will provide important information for crop management decisions. This study aimed to reveal how maturity genes E2 and E3 in the soybean cultivar ‘Enrei’ affect yields and yield formation in warm regions of Japan. ‘Enrei’ (e2e3) and three near-isogenic lines of ‘Enrei’ (e2E3, E2e3, and E2E3) were cultivated in 2016 and 2017 in Fukuyama, Japan (34°30′N, 133°23′E). Two sowing dates were set in each year (June sowing and July sowing). E2 extended the period from emergence to R1 and also the period from R1 to R7, whereas E3 extended only the period from emergence to R1. Interaction between E2 and E3 did not affect duration of the period from emergence to R1, but did affect the period from R1 to R7. Although seed yield did not differ between genotypes in the June sowings, the effects of E2 and E3 on seed yield in July sowing were both significant and interaction between E2 and E3 also observed. The total number of nodes increased in E3 genotypes in both sowing dates, especially in E2E3. Pod-set ratio was lower in E2 and E3 genotypes than in e2 and e3 genotypes in the June sowings, but did not differ between genotypes in the July sowings. The high yield of E2E3 genotypes in the July sowings was attributed to increased number of nodes and flower production while maintaining pod-set ratio. Appropriate choice of sowing date is suggested to be essential when using E3 genotypes.Abbreviations: HI: harvest index; NIL: near-isogenic line; RUE: radiation use efficiency; TDM: total above-ground dry matter; TRI: total solar radiation intercepted     

Influence of precipitations and sunshine hours on yield of paddy field grown wheat (Triticum aestivum L.) in Northern Kyushu,Japan

ABSTRACT

Relationships between wheat (Triticum æstivum L.) yield components and growing season weather conditions (e.g. temperature, precipitation, and sunshine duration) were investigated for a rice-wheat rotation paddy system situated in Northern Kyushu, Japan over a 17-year period (2000–2016). A 1.0 mm increase in precipitation from 21 to 32 days after sowing decreased wheat yield by about 27 kg ha^?1 at early seedling stage with one to two leaves (Zadoks (Z) growth stage Z1.1–1.2). Number of tillers and spikes showed significant negative correlations to the amount of precipitation during the period. An hour increase in mean daily sunshine hours from 94 to 111 days after sowing resulted in an 328 kg ha^?1 rise in grain yield at stem elongation stage with the first and second node detection (Z3.1–3.2). The grain number per square meter also showed strong positive correlations to sunshine hours during the same period. However, this positive effect of sunshine was negated when precipitation exceeded about 30 mm during the early seedling stage. Consequently, precipitations at early seedling stage and sunshine hours at stem elongation stage mostly determined wheat yield in Northern Kyushu paddy field. Increasing precipitations during the early seedling stage highlights the pressing need for effective paddy field drainage management from wheat sowing through harvest.

Abbreviations: CP: Chikushi Plains; FARC: Fukuoka prefectural Agriculture and Forestry Research Center; SARC: Saga prefectural Agricultural Research Center; DAS: days after sowing     

Growth and Yield Responses of Two Soybean Cultivars Grown under Controlled Groundwater Level in Southwestern Japan

Abstract

One of the limiting factors of soybean yield in southwestern Japan is soil moisture fluctuation from flooding to drought. The Farm-Oriented Enhancing Aquatic System (FOEAS), which consists of underdrain and sub-irrigation systems and can keep groundwater levels stable, was developed in 2005 to solve this problem. To obtain basic information on soybean cultivation using the FOEAS in southwestern Japan, we examined the growth response to groundwater level by using two cultivars (cv. Fukuyutaka and Sachiyutaka) in 2008 and 2010. Plant growth, yield, yield components and seed components (protein and oil contents) were analyzed. We also studied the effect of sowing time (normal or late). The groundwater level was controlled at depths of 20 and 35 cm or not treated (NT) as a control. The groundwater level could be kept at the target depths (20 and 35 cm) by FOEAS throughout the experimental period, but that in the NT plot fluctuated greatly. The growth and yield of Sachiyutaka might be increased by FOEAS, especially in late sowing, but the yield of normal sown Sachiyutaka was decreased in the 20-cm plot in 2010. Yield of late-sown Fukuyutaka tended to be decreased in the 20-cm plot. These results suggest that (1) the optimum groundwater level for yield of Sachiyutaka is between 20 and 35 cm, regardless of sowing time and (2) the groundwater level should not be kept at 20 cm for late-sown Fukuyutaka. Further studies are needed to determine the optimum groundwater level for each cultivar.     

Correlations of yield and quality traits between immature and mature seed stages of edamame soybean

Breeding programs must harvest edamame soybean [Glycine max (L.) Merr.] at the immature (R6) stage for yield and quality determinations, and at the mature (R8) stage for seed-source purposes. If correlations of important breeding traits between the R6 and R8 stages were strong, breeders could perform indirect selection, at least during early stages in the breeding process, thus saving resources and time. The objective of this research was to estimate correlation coefficients between the R6 and R8 stages of edamame for key traits, including yield, texture, protein, mineral, and soluble sugar content. Three edamame lines and a conventional cultivar were grown at two Arkansas locations for 3 years. Correlation coefficients were strong and positive between the R6 and R8 stages for protein (r = 0.74), iron (r = 0.73), and texture (r = 0.72), and moderate and positive for yield (r = 0.67), sucrose (r = 0.58), and calcium (r = 0.57). In conclusion, breeders could perform indirect selection for high yield, soft texture, and high protein and sucrose contents using mature seeds.     

Analysis of yield-attributing traits for high-yielding wheat lines in southwestern Japan

Development of wheat cultivars that achieve high yields despite the short growing season is essential for increasing wheat production in southwestern Japan. The objectives of this study were to assess the genetic progress in grain yield and to clarify yield-attributing traits of high-yielding wheat lines in southwestern Japan. We conducted field experiments for two growing seasons (2012–2013 and 2013–2014) using three commercial wheat cultivars (Shiroganekomugi, Chikugoizumi, and Iwainodaichi) and four high-yielding wheat lines including Hakei W1380 developed in southwestern Japan. In an ancillary field experiment, we compared a commercial cultivar, Shiroganekomugi, and a high-yielding line, Hakei W1380, in the 2014–2015 season. Across the two seasons, grain yield of high-yielding lines was generally higher than commercial cultivars. Hakei W1380 achieved the highest grain yield across the two seasons, and successfully produced more than 900 g m^?2 in the 2013–2014 season. Correlation analysis showed that recent yield progress of wheat lines in southwestern Japan was derived from enhanced biomass production and grain number m^?2. Larger numbers of grains m^?2 in high-yielding lines than in commercial cultivars were associated with higher crop growth rate at the pre-anthesis stage, and therefore higher spike dry weight m^?2 at anthesis. Genotypic differences in crop growth rate from jointing to anthesis resulted mainly from differences in leaf area index. These results indicate that further improvements in grain yield in southwestern Japan could be achieved by increasing the amount of radiation intercepted at the pre-anthesis stage and grain number m^?2.     

Modeling the effects of N application on growth,yield and plant properties associated with the occurrence of chalky grains of rice

The objective of this study was to propose a model for explaining rice responses to a wide range of N application rates in various growth attributes associated with the occurrence of chalky grains. We improved the sub-model for N uptake process of a previous rice model which was originally developed for explaining genotypic and environmental variations in the whole growth processes, considering the difference in the rate of N loss from the plant-soil system between indigenously supplied soil mineral N and fertilizer N. A total of 80 growth datasets of cultivar ‘Koshihikari’ grown at Shiga prefecture, Japan, in 2010 was utilized for the calibration and validation of the model. The rice growth model well explained the above-ground biomass growth (RMSD = 78.7 g m^?2) and rough dry grain yield (RMSD = 83.2 g m^?2) for the validation data-set, simultaneously. The simulated carbohydrate content available per single spikelet was negatively correlated with the observed percentage of the milky-white grain which includes white-cored grain (r = ?.77, p < .001) for all the data-sets of calibration and validation. On the other hand, the observed percentage of the sum of white-back and white-base grains was closely correlated with the simulated plant N content available per single spikelet (r = ?.59, p < .001). It was suggested that the present rice growth model would rationally explain the effects of N application on the occurrence of the chalky grains through the dynamic change of the carbohydrate content and plant N content available per single spikelet.     

Estimating theoretical radiation‐use efficiency for kale crops

Establishing the radiation‐use efficiency (RUE) of forage brassica crops will aid our understanding of their photosynthetic performance. The concept of RUE has been developed for cereals and legumes, but there is limited information for forage brassica crops. Three experiments defining the influence of different sowing dates on ‘Gruner’ kale (Brassica oleracea acephala L.) dry matter production were conducted at Hastings (Hawkes Bay) and Lincoln (Canterbury) in New Zealand between 2002 and 2009. These trials were also evaluated for radiation interception and RUE. Delayed sowing increased RUE in two out of three experiments across sites: from 1·93 g MJ^?1 photosynthetically active radiation (PAR) for December‐sown crops to 2·72 g MJ^?1 PAR (P < 0·001) for January‐sown crops at Hastings and from 1·50 for September‐sown crops to 2·00 g MJ^?1 PAR (P < 0·001) for November‐sown crops at Lincoln. The different sowing dates and years of experimentation provided a range of mean temperatures (from 13 to 16°C) during the vegetative period. Across years and sowing dates, RUE was strongly correlated with mean temperature (R² = 0·81) and sowing date (R² = 0·64), but weakly correlated with season length (R² = 0·11) and dry matter (R² = 0·002). There was also a strong correlation (R² = 0·83) between sowing date and mean temperature. The increase in RUE with delayed sowing was therefore mainly attributed to increased mean temperatures. Radiation‐use efficiency increased at about 0·41 g MJ^?1 for each 1°C increase from 13 to 16°C.     

Yield and dry matter productivity of Japanese and US soybean cultivars

The difference in yields of cultivars may be causing difference in soybean yield between Japan and the USA. The objective of this study was to identify the effect of the cultivar on dry matter production and to reveal the key factors causing the differences in yield by focusing utilization of solar radiation in recent Japanese and US soybean cultivars. Field experiments were conducted during two seasons in Takatsuki, Japan (34°50′), and in a single season in Fayetteville (36°04′), AR, USA. Five Japanese and 10 US cultivars were observed under near-optimal conditions in order to achieve yields as close to their physiological potential as possible. The seed yield and total aboveground dry matter (TDM) were measured at maturity as long as radiation was intercepted by the canopy. The seed yield ranged from 3.10t ha^?1 to 5.91t ha^?1. Throughout the three environments, the seed yield of US cultivars was significantly higher than that of Japanese cultivars. The seed yield correlated with the TDM rather than the HI with correlation coefficients from .519 to .928 for the TDM vs. .175 to .800 for the HI, for each of the three environments. The higher TDM of US cultivars was caused by a higher radiation use efficiency rather than higher total intercepted radiation throughout the three environments. The seasonal change in the TDM observed in four cultivars indicated that dry matter productivity was different between cultivars, specifically during the seed-filling period.     

Moisture-deficit-induced changes in leaf-water content,leaf carbon exchange rate and biomass production in groundnut cultivars differing in specific leaf area

Field experiments were conducted during two rainy seasons to study the effect of soil moisture deficit on total biomass, pod yield, harvest index (HI) and drought tolerance index (DTI) in groundnut (Arachis hypogaea L.) cultivars possessing a wide range of specific leaf area (SLA, 144–241 cm² g⁻¹). There were three soil moisture regimes: adequate irrigation (W₁), drought simulated under rain-out-shelter (W₂) and rain-fed (W₃). This experiment had two parts, in one, five cultivars were exposed to W₁, W₂ and W₃, and in a second, seven cultivars were exposed to W₁ and W₃. Using the same set of seven cultivars, pot-culture experiments were conducted to study relative water content (RWC), stomatal conductance (g_s) and single leaf carbon exchange rate (CER) during increasing moisture-deficit in two contrasting (rainy and summer) seasons. Variation in DTI was significant, and low SLA types had greater DTI under both W₂ and W₃. The ranking of SLA among cultivars was consistent between experiments conducted during the two seasons. The rate of reduction in leaf RWC during the progressive moisture-deficit was related directly to SLA (r=0.78, P<0.01). The coefficient of determination of the slopes calculated between RWC and soil moisture during the experimental period was more in the summer (r²=0.82) than the rainy (r²=0.54) season.Under increasing moisture-deficit, the low SLA types were able to maintain higher RWC, CER and g_s in both seasons. The relationships between RWC and CER (r=0.91, P<0.01), and RWC and g_s (r=0.65, P<0.01) were significant.It is suggested that under water-limited conditions there is a significant inverse relationship between SLA and RWC. The low SLA types (water use efficient) were found to be drought tolerant in terms of total dry matter production in the field studies, and maintenance of higher RWC under drought like situations in pot-culture experiments. Thus the ability of the low SLA types (higher water use efficiency, WUE) to maintain higher RWC may form the basis for the differences in drought tolerance vis a vis WUE in groundnut cultivars differing in SLA. Suggestions are made to select parents for drought tolerance or WUE, and to initiate breeding to combine traits like high HI, and WUE in terms of lower SLA. Ultimately, selection for both WUE (measured in terms of SLA) and yield traits (HI) should result in cultivars with improved performance in rain-fed agriculture.     

Evaluation of dry matter production and yield in early-sown wheat using near-isogenic lines for the vernalization locus Vrn-D1

ABSTRACT

Wheat (Triticum aestivum L.) grain yield is predicted to decrease in the future because of an increase in air temperature globally. To clarify the effects of the vernalization response gene in wheat to warmer winters, we compared dry matter production and grain yield between spring wheat ‘Asakazekomugi’ and its winter-type near-isogenic line (NIL) carrying different alleles of the vernalization response gene Vrn-D1 under early-, standard-, and late-sowing conditions. Under early-sowing conditions, dry matter production of the NIL carrying the winter allele of Vrn-D1, named Asa (Vrn-D1b), exceeded that of ‘Asakazekomugi’ from mid-March (after stem elongation in Asa (Vrn-D1b)) when the temperatures rose. Tiller number and leaf area index under early-sowing conditions were consistently higher in Asa (Vrn-D1b) than in ‘Asakazekomugi’ from mid-March onward. It was suggested that the early-sown ‘Asakazekomugi’ could not effectively absorb solar radiation to produce dry matter because of the acceleration of stem elongation caused by the Vrn-D1 gene during the cold season. The grain yield of Asa (Vrn-D1b) with early sowing was higher than with standard sowing. In contrast, the grain yield of ‘Asakazekomugi’ was lower in the early-sown crop than in the crop sown at the standard date. These results suggested that the higher grain yield of Asa (Vrn-D1b) than that of ‘Asakazekomugi’ under early-sown conditions could be due to Asa (Vrn-D1b) maintaining high dry matter production after the jointing stage by suppressing acceleration of growth caused by warm conditions after sowing.     

Harvest index is a critical factor influencing the grain yield of diverse wheat species under rain-fed conditions in the Mediterranean zone of southeastern Turkey and northern Syria

Environmental and plant factors critical to the grain yields of bread (Triticum aestivum L.), durum (T. durum L.) and emmer (T. dicoccum L.) wheat cultivars were investigated at two Mediterranean rain-fed field sites: Adana in southeastern Turkey (2009 and 2010) and Aleppo in northern Syria (2009). The grain yield (GY) and biological yield (BY) of most cultivars were higher in Adana than in Aleppo, and the lower GY in Aleppo resulted from lower harvest index (HI) and lower BY due to higher temperatures and lower rainfall. The variations in the HI among cultivars were greater in Adana than in Aleppo. The GY was closely related to the HI but not the BY across cultivars at each site, and a higher GY was accompanied by a superior conversion-efficiency of incident radiation during the grain filling period for grain yield [GY/Ra, where Ra is the cumulative radiation for 30 days after heading (D₃₀)] across all observations. The GY/Ra correlated negatively with the average temperature for D₃₀, and higher HI values resulted in higher GY/Ra. In Adana, the time from anthesis to physiological-maturity decreased as the average temperature for D₃₀ increased, resulting in a lower HI. Cultivars exhibiting the early heading trait can effectively escape the negative impacts of terminal high-temperature and water-shortage conditions on the HI. The results suggested that the HI is a critical factor for GY across diverse wheat cultivars under terminal high-temperatures and water-shortages in Mediterranean areas, and the BY is also an important factor under severe water-limitation conditions.     

Modeling crop yield using a modified harvest index-based approach: application in chickpea

The linearity of harvest index (HI) increase has been used as a simple means to analyze and predict crop yield in experimental and simulation studies. It has been shown that this approach may introduce significant error in grain yield predictions when applied to diverse environments. This error has been ascribed to variability in the rate of linear increase in HI with time (dHI/dt). Data from two field experiments indicated in chickpea (Cicer arietinum L.) that dHI/dt varied among sowing dates. This variation was related to the length of pre-seed growth phase and vegetative growth (dry matter production) during this phase and could be described by the mean daily temperature from sowing to beginning seed growth. dHI/dt increased linearly with increase in the temperature up to 17 °C when it reached to its maximum value and remained constant. Simulation of these field experiments using a chickpea crop model including a constant dHI/dt resulted in yield over-prediction for some sowing dates. However, a modified HI-based approach greatly improved model predictions. In this approach, potential seed growth rate (SGR) is calculated using the linear HI concept, but actual SGR is limited to current biomass production and the remobilisation of dry matter accumulated in vegetative organs before the seed growth period. This modification well accounted for temperature and drought effects on HI and resulted in better yield predictions under conditions of major chickpea producing areas of Iran. Therefore, we recommend that the modification to be applied in the other HI-based models.     

Micronutrient supply through granular-coated single superphosphate under field conditions

The lack of efficient methods for soil-based micronutrient fertilization in field crops at sowing remains an important limiting factor for agricultural production in low fertility soils. Therefore, we evaluated the efficiency of single superphosphate (SSP) coated with either finely ground zinc (Zn) oxide or manganese (Mn) carbonate to supply Zn to corn (Zea mays L.), and Mn to soybean (Glycine max L.) and oat (Avena sativa L.) versus traditional sources (oxide and sulfate). One experiment for each micronutrient was performed under field conditions in two sequential growing cycles: rainy season (corn and soybean) and off-season (corn and oat). Treatments were combination of Zn or Mn fertilizers (oxide, sulfate, and SSP coated with Zn oxide or Mn carbonate) at rates of 1.25, 2.5, and 5.0 kg ha^?1 of Zn or Mn, plus a control. Micronutrient fertilization showed, relative to the unfertilized control, significant increases in shoot biomass at flowering, crop yield (corn silage and soybean grain), and leaf concentration and shoot uptake of Zn and Mn during the rainy season. Residual effect of Zn on off-season corn crop represented a 43% increase in grain yield over the control. However, oat did not respond to residual Mn. The positive effects of Zn and Mn application on crop performance did not depend on fertilizer material, suggesting similar fertilizer-use efficiency. We concluded that banded application of SSP coated with either finely ground Zn oxide or Mn carbonate would be a viable option to supply these micronutrients at the time of sowing in micronutrient-deficient soils.     

Effects of Nitrogen Fertilizer Application Time on Dry Matter Accumulation and Yield of Chinese Potato Variety KX 13

Application time of nitrogen (N) fertilizer can significantly influence the yield and quality of potato tubers. The objective of this experiment was to assess the effects of N application time on dry matter accumulation in foliage and tubers, as well as on marketable tuber ratio, dry matter concentration, and specific gravity of the Chinese cultivar KX 13. The four treatments were as follows: all the 150 kg?N?ha^?1 applied at planting (T1); 100 kg N ha^?1 applied at planting and 50 kg N ha^?1 applied 1 week before tuber initiation (20 days after emergence, DAE) (T2); 100 kg N ha^?1 applied at planting and 50 kg N ha^?1 applied 1 week before tuber bulking stage (35 DAE) (T3); and 100 kg?N?ha^?1 applied at emergence and 50 kg N ha^?1 applied 1 week before tuber bulking stage (35 DAE) (T4). For all treatments, 90 kg P₂O₅ ha^?1 ((NH₄)₂HPO₄) and 150 kg K₂O ha^?1 (K₂SO₄) were applied at planting. Thirty tons per hectare of marketable tuber yield was achieved with T3, while 23 t ha^?1 marketable yield was achieved by applying all 150 kg N ha^?1 at planting (T1). Relative to treatment T1, T3 also significantly increased harvest index (HI) from 0.76 to 0.86 and marketable tuber ratio from 64.8% to 79.2%. Applying N at planting in conjunction with dressing at 20 DAE (T2) gave a high marketable tuber ratio (74%) and HI (0.86), but the lower total tuber yield led to a lower marketable tuber yield. Without N application at planting (T4), N dressing did not increase the yield and HI. Treatments with N dressing had no significant effect on specific gravity or dry matter concentration of tubers.     

Effect of pre- and post-heading waterlogging on growth and grain yield of four millets

Seeds of Panicum miliaceum, Panicum sumatrense, Setaria glauca, and Setaria italica were raised in polyvinylchloride tubes filled with soil to determine interspecific differences in waterlogging tolerance and the effect of pre- and post-heading waterlogging on growth and grain yield. Four treatments were conducted including control (no-waterlogging stress during growth). Pre-heading waterlogging treatment was initiated 17 days after sowing to heading (TC). Post-heading waterlogging treatment was initiated heading till harvest (CT). Waterlogging treatment was initiated 17 days after sowing to harvesting (TT). The grain yield of P. miliaceum, S. glauca, and S. italica decreased 16, 18, and 4%, while that of P. sumatrense increased 210% under TT treatment and this showed P. sumatrense had most waterlogging tolerance. The grain yield was more affected under TC treatment in S. italica and P. miliaceum. However, there was not significant differences the grain yield between TC and CT treatment in P. sumatrense and S. glauca. Total dry weight, total root dry weight, number of crown root, and the proportion of lysigenous aerenchyma of P. sumatrense were significantly higher than those of other millets at harvesting. Plant growth rate, total root dry weight, number of crown root, and the proportion of lysigenous aerenchyma of P. sumatrense were significantly higher than those of other millets at heading. These results suggest that P. sumatrense exhibits waterlogging tolerance by enhancing root growth characterized by a high proportion of lysigenous aerenchyma in the crown root.     

Comparison of selection indices to identify productive dry bean lines under diverse environmental conditions

This research was designed to quantify the effect of seasonal rainfall on production of dry bean (Phaseolus vulgaris L.) in the Rift Valley of East Africa, where insufficient soil moisture often limits productivity, and compare methods to identify productive lines. Twenty dry bean lines were evaluated for seed yield in a randomized complete-block design under soil moisture stress and nonstress environments during 1988, 1989 and 1992. Soil moisture stress levels were imposed by altering sowing dates (early vs. late) after the onset of the rainy season. Mean seed yield increased 8 kg ha⁻¹ for each mm of seasonal rainfall that occurred during the growing season. Lines differed in response to soil moisture stress, and their response varied with environments. Six selection indices, including arithmetic mean (AM), geometric mean (GM), drought response index (DRI), susceptibility index (S), response to drought (RD), and percent reduction (PR), were calculated for each line to determine correlations between indices and yields in stress (Y_s) and nonstress (Y_ns) environments. AM and GM were the only indices positively correlated with both Y_s and Y_ns. AM had the largest correlation with Y_ns (r=0.90) whereas GM had the largest correlation with Y_s (r=0.93). DRI, PR and S were correlated with Y_s (r=0.86, −0.82 and −0.83, respectively) but not with Y_ns. Conversely, the index RD was correlated with Y_ns (r=0.73) but not Y_s. The indices PR and S evaluated change in line performance across environments rather than line performance in either environment. GM and AM appear to be the most useful selection indices for identifying high yielding lines for both nonstress (early sown) and stress (late sown) conditions in the Rift Valley, while DRI has potential for use as a selection criteria only for stress environments.     

播种方式和种植密度对冬小麦根系生长和产量的影响

为探究播种方式和种植密度对冬小麦根系生长和产量的影响,以新冬22号为材料,采用二因素裂区试验设计,主区设条播（DR）和匀播（UN）2种播种方式,副区设150万粒·hm^-2（D150）、225 万粒·hm^-2（D225）、300万粒·hm^-2（D300）和375万粒·hm^-2（D375）4种种植密度,比较分析了不同播种方式和种植密度下冬小麦根系形态特征、根系伤流量和产量的差异。结果表明,随种植密度的增加,小麦总根干重、总根长呈先增后减趋势,单株次生根数、根系伤流量呈减小趋势。与条播相比,匀播下小麦总根干重、总根长显著增加,差异主要在0~30 cm土层;单株次生根数、根系伤流量增加,差异主要在生育中后期;产量显著提高（增幅9.89%）,其中以D225处理最大。综上,匀播能够促进小麦根系的生长,提高根系活性,有利于高产;在本试验条件下匀播小麦以225万粒·hm^-2种植密度最佳。     

Effects of twice harvesting on total dry matter yield of rice

We examined the effect of twice harvesting of forage rice with the first harvest at the full heading stage on total dry matter yield in the cultivars Taporuri, Mohretsu, and Hinohikari and in line Saikaishi 253 in southwestern Japan. Taporuri produced the highest total dry matter yield, with a value 60% higher than that of Hinohikari. The first crop of Taporuri had a longer duration of vegetative growth than those of Mohretsu and Hinohikari, and had the highest dry matter yield because of its greater weight per tiller than Hinohikari and its more tillers per square meter than Saikaishi 253, which had a similar duration of vegetative growth. The second crops of Mohretsu, Taporuri, and Saikaishi 253 had longer vegetative growth and higher dry matter yields than Hinohikari. Dry matter yields of both crops were closely related to the duration of vegetative growth and the weight per tiller, but not to tillers per square meter. These results suggest that cultivars with a long duration of vegetative growth, high weight per tiller, and adequate tillers per square meter can produce high dry matter yield in both crops. There was a significant interaction (P < 0.05) in total dry matter yield between cultivar or line and cultivation type. The total dry matter yield of Taporuri in twice harvesting was about 10% higher than that in once harvesting, whereas that of Hinohikari was about 10% lower. The suitability for twice harvesting ([total dry matter yield in twice harvesting]/[total dry matter yield in once harvesting]) was significantly positively correlated (r = 0.875) with the increase in dry weight before the full heading stage, but significantly negatively correlated (r = −0.903) with the increase in dry weight between full heading and the yellow ripe stage. Thus, cultivars with a high increase in dry weight before full heading appear to be more suitable for twice harvesting than those with a high increase between full heading and the yellow ripe stage. In addition, our study showed that twice harvesting can prevent lodging in Taporuri, thereby increasing the suitability of this cultivar as a forage rice. Our results suggest that twice harvesting can be performed in southwestern Japan and warmer regions.     

The response of a perennial ryegrass (Lolium perenne L.) seed crop to nitrogen fertilizer application in the absence of moisture stress

Responses of perennial ryegrass (Lolium perenne L.) to nitrogen (N) fertilizer application rates and timings vary widely, because water is often limiting. Yield response to N fertilizer application during autumn, late‐winter and spring, and the associated efficiency of use of these inputs, was assessed under conditions of non‐limiting soil moisture during two, one‐year lysimeter studies in Canterbury, New Zealand. There were significant (P < 0·05) increases in seed and herbage yields with increasing N fertilizer application. Seed yields differed with year; greatest yields were 300 g m^?2 in 1996 and 450 g m^?2 in 1997. Seed head numbers (r²=0·77), seeds head^?1 (r²=0·92) and herbage yield (r²=0·92) were the major determinants of seed yield in both years. Irrigation required to maintain the soil between 70% and 90% of field capacity was directly related (r²=0·94 and 0·99 in 1996 and 1997 respectively) to increases in herbage yield. Seed yield, seed quality (thousand seed weight and percentage of seed > 1·85 mg), efficiency of water use, efficiency of N fertilizer use and apparent N fertilizer recovery were greatest when N fertilizer was applied at a rate of 50 kg N ha^?1, 50 or 100 kg N ha^?1 and 150 kg N ha^?1 in autumn, late‐winter and spring respectively; further increases in spring N fertilizer stimulated vegetative growth, but not seed yield. As a management strategy, applying N fertilizer to match the N requirements of the crop during the reproductive stage of growth will result in high yields of high quality seed while minimizing environmental impact.     

立体匀播和密度对冬小麦光合、干物质积累分配及产量的影响

为给小麦立体匀播栽培推广提供理论依据,选用小麦品种新冬22号和新冬46号为供试材料,采用裂区设计,主区种植方式设立体匀播和常规条播2个处理,副区种植密度设150万株·hm~(-2)(D_(150))、225万株·hm~(-2)(D_(225))、300万株·hm~(-2)(D_(300))和375万株·hm~(-2)(D_(375))4个处理,研究了种植方式和密度对冬小麦光合、干物质积累与分配、产量及其构成因素的影响。结果表明,与常规条播比较,立体匀播方式下小麦群体生育后期中、下部叶的LAI、SPAD值和净光合速率显著提高;植株重、干物质转运量、干物质转运效率和干物质转运对籽粒产量贡献率增大,而植株成熟期营养器官干物质分配率降低;随着种植密度增大,茎鞘干物质分配率上升,叶片干物质分配率减小,而颖壳及穗轴、籽粒干物质分配率则无显著变化。与常规条播相比,立体匀播方式下新冬22号和新冬46号主茎穗粒重平均降低7.95%和4.43%,而分蘖穗粒重平均提高11.54%和5.06%,穗数显著提高(17.31%和17.68%),产量提高6.40%和9.84%,以D_(225)处理产量最高;穗粒数分别降低2.23%和1.71%,千粒重分别降低4.38%和4.54%。由此可知,立体匀播方式提高了小麦群体生育后期中、下部叶片叶面积指数和净光合速率,增大了植株干物质积累量,促进了营养器官干物质向分蘖穗籽粒中转运,并主要通过增加群体穗数和分蘖穗穗粒重提高产量;最佳的种植密度为225万株·hm~(-2)。