Effect of crop rotation,cultivar and nematicide on growth and yield of potato (Solanum tuberosum L.) in short rotations on a marine clay soil

Summary The effects of cropping frequency on the yield of potato and on the development of soil-borne diseases was studied from 1979 to 1985 in a crop rotation experiment on a marine clay soil. Tuber yield decreased markedly with increasing cropping frequency. The yield of cv. Hertha was reduced by 27% in continuous cropping and by 15% in a wheat/potato or sugar beet/potato rotation, when compared with the rotation wheat/sugar beet/oats/potato. However, a pot experiment showed that yield depression in continuous cropping depended on the cultivar used. Crop growth declined in the second part of the growing season, and senescence accelerated as the cropping frequency increased.Verticillium dahliae was the most important yield-reducing factor. Root infection by this fungus was stimulated by the root-lesion nematodePratylenchus neglectus.     

Simulating growth,development, and yield of tillering pearl millet: II. Simulation of canopy development

Tillering is an important adaptive feature of pearl millet (Pennisetum americanum L.) to the unpredictable growing conditions of dry areas of the semi-arid tropics. Yet, this feature has largely been ignored in the development of simulation models for pearl millet. The objective of this paper is to parameterise and validate a leaf area module for pearl millet, which dynamically simulates crop leaf area from the leaf area of individual axes through simulating inter-axis competition for light. To derive parameters for the model, four cultivars (contrasting in phenology and tillering habit) were grown under well-watered and well-fertilised conditions across a range of plant densities in three experiments at two locations in India. For selected plants, observations on the number of primary basal tillers and on the number of visible, fully expanded, and senesced leaves on each axis were made twice a week throughout the growing season. Occurrence of panicle initiation (PI) was observed in two experiments only, but data were complemented by published and unpublished data, obtained for comparable cultivars. Parameters were obtained for the time from emergence to PI as a function of daylength, the leaf initiation rate, the rate of leaf and tiller appearance and the leaf senescence rate; parameters for leaf size were determined in a previous paper. Our parameter estimates compared well with published data and were, with the exception of time to PI and leaf size, mostly independent of cultivar, axis and density. Genotypic effects on productive tiller number could be attributed to differences in main shoot leaf size. Validation of the leaf area module showed that the module adequately reproduced the effects of density, photoperiod and genotype on the leaf area of individual axes and on productive tiller number. This was despite the fact that the reduction in leaf area of non-productive tillers was achieved in the module through a reduction in leaf size, whereas the crop reduced leaf area through a reduction in leaf number. Our results indicate that LAI of a tillering crop can be simulated adequately by simulating LAI from individual leaf area and incorporating the effects of competition for light.     

Path Analysis of Tiller Density of Winter Wheat Demonstrates the Importance of Practices that Manipulate Clod Size Based on Soil Moisture at Seeding in the Rice–Wheat Cropping System

Abstract

The moisture of paddy soil after rice cropping is a major impediment to the establishment, tillering and yield of winter wheat in the rice?wheat (R?W) cropping system. We examined the seedling establishment ratio, based on soilmoisture at seeding by path analysis of nine soil/plant traits in the farmer's fields in Western Japan where the R?W cropping system was being used, to establish a strategy for improving tiller density by optimizing the seedling establishment ratio. The clod size of surface soil, which showed a significant positive correlation with soil moisture at seeding, had a significant negative direct effect on the seedling establishment ratio. The reduction in seedling establishment ratio, together with fewer tillers per plant, resulted in a significant decrease in tiller density. The sum total of contribution of soil moisture contents to tiller density via clod size was smaller than that of seeding rate, and similar to that of the amount of nitrogen (N) basal dressing. This indicates that manipulating clod size based on soil moisture at seedingprovides an opportunity for maintaining tiller density, as well as changing the amount of N basal dressing with the soil moisture conditions after rice cropping.     

Crop rotation and N fertilization effects on growth,yield, and disease incidence in potato

Crop rotation can be an effective mechanism for reducing disease incidence and contributing nitrogen (N) to succeeding crops. Interactions of plant pathogen suppression and soil nutrient availability may also exist, adding to the cropping system complexity. This study examined the impact of crop rotation, N fertilization, and their interaction on growth, yield, andRhizoctonia solani incidence in potato (Solanum tuberosum L. Norwis). Potato was grown continuously and in two-year rotations with annual alfalfa (Medicago sativa L. Nitro), hairy vetch (Vicia villosa Roth), white lupin (Lupinus albus L. Ultra), and oat (Avena sativa Astro). Fertilizer was banded at potato planting with 0, 45, 90, 135, 180, or 225 kg N ha^?1 as (NH₄)₂SO₄. Approximately 58% of continuous potato possessed stem lesions caused byR. solani, but only 12 to 22% of potato stems from other rotations possessed lesions. Tuber dry weight was affected by crop rotation in 1989, a dry year, but not in 1990. Apparent N fertilizer replacement values for hairy vetch, Nitro alfalfa, white lupin, and oat were 65, 43, 26, and 11 kg N ha^?1, respectively. All crop rotations studied appeared to enhance potato production by reducing stem infection byR. solani. Vetch and alfalfa provide additional benefits through their N contributions.     

Causes of differences in growth pattern,yield and quality of potatoes (Solanum tuberosum L.) in short rotations on sandy soil as affected by crop rotation,cultivar and application of granular nematicides

Summary A crop rotation experiment was carried out on a light sandy soil in 1979–1986 to study the effects of the frequency of potato cropping on yield, quality and on the occurrence of soil-borne pathogens other than potato cyst nematodes. Tuber yield decreased markedly with increasing cropping frequency, but also depended on what crops were grown in rotation with potato. Growth during the early part of the season, as well as the length of the growing period, were reduced in short rotations. The fungiVerticillium dahliae andRhizoctonia solani, and root-knot nematodes (Meloidogyne spp.) were the most important yield reducing pathogens. The effects of rotation depended on the cultivar used. The percentage of mis-shapen tubers increased with increasing cropping frequency and after application of granular nematicides, but the incidence of common scab (Streptomyces scabies) was not affected.     

Does higher yield potential improve barley performance in Mediterranean conditions?: A case study

Barley is one of the most widely cultivated crops in rainfed areas of the Mediterranean, where drought is the main factor that limits yield. Knowledge of the physiological traits responsible for adaptation of barley cultivars to Mediterranean environments may be relevant for future breeding strategies. Yield potential versus drought tolerance is an open debate. Here, we studied two barley cultivars (Graphic and Kym), of similar time to anthesis and crop duration, that are widely cultivated in the western Mediterranean. Grain yield was evaluated in 41 field trials and ranged (averaged for the 16–32 cultivars assayed in each trial) from 0.7 to 9.1 Mg ha⁻¹. Yield components and carbon isotope discrimination (Δ¹³C) of grains was analysed in another two trials. Graphic production was greater than Kym in all conditions. This greater yield was sustained mainly by more ears per unit ground area, which may be attributable to higher growth potential during tillering. Moreover, Graphic showed greater Δ¹³C of kernels, indicating improved water status even at the end of the crop cycle. To examine differences in early growth, these cultivars were grown in optimal conditions and then photosynthetic activity and biomass analysed at the end of tillering. Graphic showed greater above-ground and root biomass as well as total leaf area per plant and per tiller than Kym, and also tended to have more tillers per plant, but its shoot-to-root biomass ratio was lower. Nitrogen content per unit leaf area was correlated negatively with plant and with tiller leaf area and positively with the shoot-to-root biomass ratio. Photosynthetic rate per unit leaf area was lower in Graphic and positively related to a lower nitrogen content, whereas stomatal limitation of photosynthesis and water use efficiency was similar in the two cultivars. Ribulose 1,5-biphosphate regeneration capacity contributed to the lower photosynthetic rate of Graphic. Moreover, quantum yield of photosystem II (PSII) electron transport was also lower in Graphic than Kym, which suggests that mechanisms other than leaf structure also contributed to the higher photosynthetic capacity of the former. Nevertheless, as result of differences in leaf area, total plant photosynthesis was greater in Graphic.The results indicate that the higher yield of Graphic under a wide range of Mediterranean conditions may be sustained by increased plant growth and total photosynthesis during tillering, although the photosynthetic capacity per unit leaf area is lower than that of Kym. Graphic has a more extensive root system than Kym, subsequently improving its water status in later stages of the crop cycle. Nitrogen content per unit leaf area is a good indicator of the growth and photosynthetic activity of barley plants in the early stages of the crop cycle.     

Alternative cropping systems can have contrasting effects on various soil-borne diseases: Relevance of a systemic analysis in vegetable cropping systems

Vegetable production makes an intensive use of pesticides, and a major challenge is to build alternative cropping systems that can control pests and diseases with fewer uses of chemical products. An on-farm analysis was conducted in Southeast France to assess the efficacy of several cropping systems in simultaneously controlling two major pests: root-knot nematodes (Meloidogyne spp.) and lettuce drop due to Sclerotinia sclerotiorum. Ten cropping systems resulting from the combinations of three crop sequences and two alternative techniques, solarization and green manure, were assessed during two years. The use of solarization once a year or once every two years limited the occurrence of S. sclerotiorum. Sorghum green manure tended to increase S. sclerotiorum incidence; the effect was positively correlated with green manure duration. Especially when no vegetable was cropped in summer, the green manure crop duration was lengthened and this probably created soil conditions favorable to the development of the fungus. The incidence of root-knot nematodes was largely dependent on crop rotation: a melon crop in summer increased its incidence on the subsequent lettuce crops whereas a summer sorghum cover crop had no effect. The cropping systems that limited Sclerotinia development in soil tended to support the root-knot nematode populations. These results should motivate farmers and advisers to adopt a systemic analysis and take into account the various interactions among inoculum level, soil characteristics, crop rotations, and technical management options for designing sustainable vegetable production systems.     

Effects of soil-borneRhizoctonia solani Kühn on yield and quality of ten potato cultivars

Summary The effects of soil-borneRhizoctonia solani on yield and quality of potato were studied by an extensive individual plant sampling procedure. From 1983 to 1986, stem canker and stolon pruning were examined in 10 768 plants growing on a sandy soil. Tuber yield and quality and haulm yield per plant were also recorded. The degree of attack byR. solani depended on the cropping frequency of potato. Severe and very severe stem and stolon attacks decreased fresh yield, dry matter yield and dry matter content of tubers and increased the number of deformed and small tubers, whereas the effect on haulm yield and stem number was small. Potato cultivars differed in susceptibility toR. solani, but yield response did not differ significantly between cultivars at the same levels of stem and stolon infection.     

Influence of crop rotation on selected chemical and physical soil properties in potato cropping systems

Crop yields are often increased through crop rotation. This study examined selected soil chemical and physical properties that may constitute the N and non-N related effects of crop rotation in potato cropping systems. Potato (Solanum tuberosum L. Norwis) was grown continuously and in two-year rotations with annual alfalfa (Medicago sativa L. Nitro), hairy vetch (Vicia villosa Roth), white lupin (Lupinus albus L. Ultra), and oat (Avena sativa Astro). Hairy vetch contributed more residue N than any other crop rotation, ranging from 110 to 119 kg N ha^?1. Inorganic N concentrations in potato soils were related to the previous crop’s residue N contents, and were highest following vetch and alfalfa and lowest following oat and potato. The highest mineralizable N concentration was found following vetch (46.6 mg N kg^?1). Saturated soil hydraulic conductivity in potato following all rotations ranged from 9.88 to 11.28 cm h^?1 compared to 5.71 cm h^?1 for continuous potato. Higher soil water contents were maintained in the 30 to 45 cm depth for all rotations compared to continuous potato. Thus several parameters indicate substantial N effects associated with particular crop rotations. Soil hydraulic conductivity and soil water status may also represent significant components of the rotation effect not directly related to N for these cropping systems.     

Effects of crop rotation and granular nematicides on the incidence ofVerticillium dahliae Kleb. andColletotrichum coccodes (Wallr.) Hughes,in potato

Summary The incidence ofVerticillium dahliae andColletotrichum coccodes was studied in a crop rotation experiment on sandy soil from 1983 to 1986. Early in the growing season the percentage of stems infected byV. dahliae increased with increasing cropping frequency of potato, depending on the cropping sequence, and decreased with the application of granular nematicides. However, later in the growing season the initial differences decreased.C. coccodes infections of stems were not affected by these factors. The percentage of plants infected byV. dahliae closely correlated with the percentage of plants with wilt symptoms but this relationship was absent forC. coccodes. Early in the growing season, the more vigorous the plants, the greater the level ofV. dahliae infection. Soil infestation withV. dahliae increased with increasing cropping frequency of potato but was not affected by annual applications of granular nematicides.     

The physiology of tiller death in grasses.

A reproducible method of causing tiller death on individual ryegrass (Lolium perenne L., cv. S23) plants is described. This was achieved by subjecting whole plants grown previously for 7 weeks in full light (100%) and full nutrient (100%) to either light stress (17.5% or 2.5%) or nutrient stress (10% or 0%) or various combinations of light and nutrient stress. Detailed records were made of tiller appearance, position and weight, and the probability of tiller death was calculated. Analysis of each plant indicated that the smallest tiller, which was often, but not always the youngest, was the most vulnerable when the whole plant was stressed. Tiller position was relatively unimportant in determining survival. The results are discussed in relation to tiller mortality in natural populations and crop communities.     

Photoperiod shift effects on yield characteristics of rice

Edible yield must be maximized for each crop species selected for inclusion in the Controlled Ecological Life-Support System (CELSS) proposed by NASA to support long-term manned space missions. In a greenhouse study aimed at increasing biomass partitioning to rice (Oryza sativa L.) grain, plants of the high yielding semi-dwarf rice cultivar Ai-Nan-Tsao were started in pots under 8-h photoperiods at a density of 212 plants m-2. After different periods of time under 8-h photoperiods, pots were switched to continuous light for the remainder of the cropping cycle. Continuous light did not delay time to first panicle emergence (60 d) or time to harvest (83 d). There was a positive correlation between the length of continuous light treatments and nongrain biomass. Grain yield (1.6 +/- 0.2 g plant-1) did not increase in continuous light. Yield-efficiency rate (grain weight per length of cropping cycle, canopy volume, and weight of nongrain shoot biomass) was used to compare treatments. Small Ai-Nan-Tsao rice canopies grown under 8-h photoperiods were more efficient producers of grain than canopies grown under continuous light for a portion of the rice cropping cycle.     

Contribution of main stem and tillers to durum wheat (Triticum turgidum L. var. durum) grain yield and its components grown in Mediterranean environments

Under terminal drought conditions, cereal varieties with limited tillering have been suggested to be advantageous, because they have fewer nonproductive tillers, thereby limiting water consumption prior to anthesis. In this study, four field trials were conducted over two growing seasons in southern Spain, under rainfed and irrigated conditions. Twenty-five genotypes were studied to evaluate the contribution of the main stem (MS) and tillers to grain yield and its components. Significant differences were found among genotypes for these contributions under non-stressed environments, but these differences were not significant under water-stress conditions. The contribution of the MS to plant grain yield was higher than that of tillers (68% vs. 32%) and was stable between years in irrigated trials. However, in the rainfed trials, MS contributed differently depending on year-to-year climate variations. Thus, under favorable weather conditions the contribution of MS to grain yield was higher than in the unfavorable year (85% vs. 59%). In irrigated environments, MS and tiller grain yield depended on the number of grains per spike, spikelets per spike, and thousand kernel weight (TKW). Under water-limited conditions, MS yield depended on the number of grains per spike and grains per spikelet, whereas the number of spikelets and TKW had less influence on MS grain yield. Furthermore, under water-stress conditions, high tillering genotypes showed yield levels similar to the genotypes with restricted tillering. Additionally, there was no significant evidence of a positive or negative effect of maximum tiller number on grain yield under rainfed conditions.     

Varied previous crops on improving oilseed flax productivity in semiarid Loess Plateau in China

To investigate the effects of crop rotation on oilseed flax growth and yield, three season experiments were carried out in semi-arid area of Dingxi, Gansu from 2017 to 2019. The designed 6 rotational systems were FFF (flax-flax-flax), PFF (potato-flax-flax), WPF (wheat-potato-flax), FPF (flax-potato-flax), PWF (potato-wheat-flax) and FWF (flax-wheat-flax). Flax growth and yield investigation results showed that crop rotation increased leaf area duration, dry matter accumulation, seed nitrogen accumulation, water and nitrogen used efficiency, compared with continuous cropping of flax. Flaxseed yields in rotation systems were 22.23%–44.11% greater than those of continuous cropping system. Those in wheat and potato stubbles had higher tiller number (21.43% and 29.46%), more branches (14.24% and 6.97%), effective capsules (26.35% and 28.79%), higher water use efficiency (40.26% and 33.5%), higher nitrogen partial factor productivity (33.85% and 31.46%) and dry matter (41.98% and 25.47%) than those in oilseed flax stubble. It concluded that crop rotation system was an effective measure for oilseed flax productivity in semi-arid area by improving yield components and promoting biomass.     

Effects of moldboard plowing,chisel plowing and rotation crops on the Rhizoctonia disease of white potato

Two tillage practices, chisel plowing (30 cm) and deep moldboard plowing (22 cm), and five rotation crops (oats, lupine, buckwheat, broccoli and peas) were studied for their effects on the soil population ofRhizoctonia solani AG-3 and on Rhizoctonia disease on potato. All rotation crops were harvested except buckwheat, which was treated as a green manure crop. Chisel plowing significantly reduced (p = 0.05) the incidence and severity of stem lesions on potato caused byR. solani AG-3. In 1990, oats after moldboard plowing significantly increased disease when compared to other crops and broccoli after chisel plowing decreased disease severity. Soil populations ofR. solani AG-3 were significantly lower with chisel plowing. No interactions between tillage and rotation crops were observed. Rhizoctonia solani Kühn is a soil inhabiting plant pathogen found worldwide that affects many plant species including white potato (Solanum tuberosum L.).R. solani attacks potato at one or more stages in development resulting in distinct disease symptoms (25) often termed the Rhizoctonia disease complex of potato. In Maine, only strains AG-3 and AG-5 ofR. solani (4, 5) have been identified as attacking potato and causing four distinct types of symptoms: 1) black scurf (sclerotia) on tubers, 2) stem cankers, 3) aerial tubers and top rosetting, and 4) killing of sprouts. Crop rotation has been reported to reduce the incidence and severity ofR. solani on potato, but no single rotation method controls completely or to a high degree of reliability (11, 23, 24, 26). Deep moldboard plowing has been shown to reduce diseases caused byR. solani andSclerotium rolfsii Sacc. in crops other than potatoes (2, 7, 15, 19, 20). However, Gudmestadet al. (6) reported that deep moldboard plowing increased the severity ofR. solani on stems and stolons of potatoes. The reduction of diseases caused byR. solani andS. rolfsii by moldboard plowing is attributed to low inoculum densities in the upper soil layer by the burial of sclerotia to depths where germination and infection were prevented (14, 15, 19, 20). However, disking to a depth of 5–7 cm did not affect disease as the inoculum remained in the root zone (14, 15). Gurkin (7) states that the rationale for deep moldboard plowing is to promote decay of organic matter, remove organic matter from the infection court and to bury the sclerotia below the infection court. Cultural control techniques are largely preventive and are designed to reduce the quantity or the activity of inoculum by means of crop rotation, tillage practices, green manure crops, etc. (22). This study was conducted to determine individual effects and possible interactions of deep moldboard plowing versus chisel plowing in various rotation crops on the presence ofR. solani AG-3 in the soil and on the incidence of Rhizoctonia disease complex of potato.     

豇豆-水稻轮作模式下水稻生长的不均匀性

冬季瓜菜之后轮作水稻是海南省一种重要的栽培模式。为了充分利用前作的肥效,一般后作水稻都会减少肥料的使用,这时前作肥料条施所导致的田间肥力不均会较大地影响后作水稻的生产。本研究以豇豆-水稻轮作为对象,以杂交稻品种‘聚两优747’为材料,于分蘖末期、成熟期分别在不同肥力下生长表现强势（T₁）和生长表现弱势（T₂）的行间取样,分析了豇豆-水稻轮作模式对后作水稻的生长发育、产量构成和稻米品质的影响。研究结果显示,生长在不同肥力行间的植株,在分蘖末期,其生长发育性状上有明显的差异,如株高、分蘖数、地上部干重、倒三叶叶面积、植株含氮量等方面差异显著,其中,T₁植株根、茎、叶的含氮量分别比T₂植株的高117.1%、368.8%、72.3%,差异都达到极显著水平;在成熟期,与产量构成相关的指标,如有效穗数、实粒数、结实率、千粒重等方面存在显著差异,尤其是T₁植株的穗数和结实率分别比T₂植株高64.0%和9.3%,差异达极显著水平;在稻米品质方面,虽然在出糙率、精米率、精米的长和宽及长宽比、糊化温度和直链淀粉含量等方面没有显著差异,但在整精米率、胶稠度、蛋白质含量、垩白粒率方面存在显著差异,如T₁的垩白粒率比T₂低4.5%,而T₁的整精米率则比T₂高5.5%,差异都达到极显著水平。因此,在豆稻轮作的情况下要获得水稻的高产优质,需要制定合理的栽培技术方案,改进耕作技术、均衡前作的遗留肥力,并注意在水稻当季合理施肥。     

Leaf number as a criterion for determining defoliation time for Lolium perenne: 2. Effect of defoliation frequency and height

The object of this study was to determine the importance of frequency and height of defoliation on regrowth potential of Lolium perenne. Defoliation interval was based on stage of the regrowth cycle, as indicated by leaves per tiller.
Simulated swards of Lolium perenne cv Yatsyn were grown as individual plants in a glasshouse kept at a day/night temperature of 25°C/15°C.
Treatments imposed were defoliation at 2, 5 or 12 cm residual height, and low and high water soluble carbohydrate (WSC) level obtained by varying defoliation interval, i.e. defoliating at the 1-leaf or 3-leaf stage of the regrowth cycle. Regrowth after frequent short defoliations was only 65% of the less frequently defoliated plants taken over the full regrowth cycle. This was associated with a lower stubble WSC content (2·15 vs 17·5% in stubble) and a twenty-seven-fold difference in the amount of WSC in the stubble per plant. This difference in total WSC was a combined effect of more and heavier tillers and higher WSC content in stubble of plants defoliated less frequently at the end of the regrowth cycle. The regrowth of plants with WSC levels depleted by frequent defoliation when defoliated at 2 cm was significantly below that of those defoliated at 5 and 12 cm.
The results indicate the desirability of defoliating plants at the 3-leaf stage of the regrowth cycle. This not only allows the full regrowth potential to be expressed in that growth cycle, but also in the next cycle, by allowing the replenishment of WSC reserves and optimizing tiller status. The potential to regrow appears then to be based more on the total amount of WSC than the proportion of WSC in stubble.     

The impact of defoliation frequency and nitrogen fertilizer application in spring on summer survival of perennial ryegrass under grazing in subtropical Australia

Abstract This field study investigated the effect of timing of nitrogen (N) fertilizer application in spring on the survival of grazed perennial ryegrass (Lolium perenne cv. Dobson and Yatsyn) over summer in a subtropical environment. There were five N fertilizer treatments: no applied N, 46 kg N ha^?1 on 22 October or 22 November or 22 December, or on 22 October and again on 22 December. Water‐soluble carbohydrate (WSC) concentration of perennial ryegrass plants entering the summer was altered by varying defoliation frequency, with defoliation interval based on the number of leaves per tiller. Frequent defoliation was set at a regrowth level of one leaf per tiller and less frequent defoliation at a regrowth level of three leaves per tiller, over a total of two by three‐leaf per tiller regrowth periods. Application of N fertilizer was found to have no significant effect (P > 0·05) on survival of perennial ryegrass plants over summer. On the other hand, defoliation had a marked effect on perennial ryegrass persistence, with frequent defoliation decreasing ryegrass plant density (51 vs. 88 plants m^?2; P < 0·001) and increasing the density of tropical weed grasses (99 vs. 73 plants m^?2; P < 0·001) by autumn. Frequently defoliated plants had a lower stubble WSC content on a per plant basis than less frequently defoliated plants in spring (103 vs. 201 mg per plant; P < 0·001) and summer (59 vs. 101 mg per plant; P < 0·001). The lower WSC content was associated with a smaller root system in spring (1·50 vs. 2·14 g per plant; P < 0·001) and autumn (1·79 vs. 2·66 g per plant; P < 0·01), and this was reflected in 0·29 more plants being pulled from the soil by livestock between November 1996 and April 1997. Rhizoctonia fungus was associated with roots of pulled plants, but not with roots of seemingly healthy plants, indicating that this fungus may have a role in a weakened root system, which was more prone to sod pulling. Nitrogen applied in October and November resulted in a reduced WSC concentration, although the effect was restricted to 1 month after N application. The present study indicates that survival of perennial ryegrass plants over the summer in a subtropical region is prejudiced by frequent defoliation, which is associated with a lower WSC concentration and a shallower root system. Under grazing, sod pulling is a reflection of this weaker root system and contributes to plant mortality.     

四川小麦分蘖冗余及理想群体构成研究

为探究四川小麦分蘖冗余及理想群体构成,以5个典型冬小麦品种为材料,在分蘖始期至拔节期每2d剪一次分蘖,设置3个处理[仅保留主茎,剪除所有分蘖(B0);保留主茎和1个大分蘖(B1);保留主茎和2个大分蘖(B2);不剪分蘖(CK)],对成熟期小麦株高、穗部性状和单株产量进行调查分析。结果表明,5个品种间各性状对剪除分蘖的反应表现较一致。单株穗数以B0处理最低(1.00穗),B1、B2和CK处理单株穗数在同一水平(1.96~1.98穗);B0处理下穗粒数(49.5粒)、千粒重(53.2g)、穗长(11.3cm)、有效小穗数(17.7个)较CK显著增加,但株高(86.5cm)和单株产量(2.54g)均最低;B2处理的单株产量(4.27g)介于B1(4.39g)和CK(4.13g)之间,但与二者差异均不显著;B1处理下株高(88.1cm)适中,主茎和分蘖的穗长(11.0、10.6cm)增加,有效小穗数(17.8、16.4个)增多,最终主茎和分蘖的穗粒数(47.4、39.5粒)显著高于B2(44.2、34.7粒)和CK(43.8、36.0粒),主茎和分蘖的千粒重(50.7、52.5g)略高于B2(50.3、50.9g)和CK(49.6、51.3g),穗数、穗粒数、千粒重协调,单株产量(4.39g)最高。因此认为,保留主茎1个分蘖处理消除了冗余分蘖对资源的浪费,减少了内耗,是四川小麦优质、低耗、高产的最佳茎蘖组合。