EFFECTS OF CULTURAL TREATMENTS ON WHEAT AND ON THE INCIDENCE OF EYESPOT, LODGING, TAKE-ALL AND WEEDS. Field Experiments 1945–8

An experiment was made on the fourth, fifth and sixth successive crops of winter wheat to determine the effects of various treatments on the troubles which result from close cereal cropping. Eyespot and lodging were prevalent in the first year (1946); weeds in the second; eyespot, lodging, take-all and weeds in the third.
Spraying with H₂SO₄ reduced the incidence of eyespot, lodging and weeds, and increased yield of grain on plots which received sulphate of ammonia (by 2.7, 2.2 and 10.0 cwt./acre in successive years).
Sulphate of ammonia increased the incidence at harvest of eyespot and lodging, reduced take-all and consistently increased yield of straw. Eyespot and lodging reduced the effect of the fertilizer on yield of grain, take-all increased it.
Increase in seed rate increased the incidence of severe eyespot and of take-all; it increased lodging except when plants were dwarfed by take-all.
Weight of straw and percentage straws with severe eyespot lesions independently affected lodging, together accounting for 51% of the variance in percentage area lodged at harvest and 64 % of that lodged 33 days earlier.
Mean yields of grain on untreated plots sown with 3.3 1/2 bushels seed/acre fell from 26.0 to 22.5 to 11.7 cwt./acre in successive years, whereas yields of 28.4, 29.9 and 29.1 cwt./acre were obtained on sprayed plots sown with 1 1/2.2 bushels seed/acre which received 4 cwt./acre sulphate of ammonia, showing that high yields were maintained when eyespot, lodging, take-all and weeds were controlled.
By 1948 yields of grain on unsprayed plots had fallen to the level of those on similarly manured plots on the continuous wheat experiment on Broadbalk field. Spraying increased grain by amounts similar to those resulting from one year's fallow on Broadbalk; but fallow had its greatest effects on plots with low nitrogen, spraying on those with high nitrogen.     

Observations on the effects of mildew, Erysiphe graminis, on growth of spring and winter barley

In field plots, early and severe attacks of powdery mildew on spring barley plants greatly reduced the vigour, decreased the amount of root, the number of ear-bearing tillers and the grain size. In less severe, or later attacks, mildew mainly affected the grain size. On winter barley, where mildew attacked both in autumn and in spring, yield was decreased more than when only a spring attack occurred. The early attack retarded development of the root system, increased winter kill and decreased the number of ears reaching maturity. Because early mildew attack affects yield, it is not always possible to correlate yield loss with intensity of mildew at any one growth stage of the crop.     

Competition of wild oat with wheat in comparison to the wheat itself

In a glasshouse experiment, an increase of the number of wheat plants per pot caused the plants to became taller, have more ears and a greater grain yield per pot, while the number of tillers decreased and the straw mass did not change. The N and P contents in straw and N in grain also trended to decrease, while the translocation of these nutrients to the grain increased. The increase of wild oat plants (Avena sterilis spp.macrocarpa Mo.) per pot, produced a decrease of the growth attributes, grain yield and N accumulation in grain of wheat per pot. Wild oat competition with wheat was higher than the wheat competition with itself. Such competition affected the height, number of tillers and ears, the fertility index of the shoots, the straw and grain mass, and the total accumulation of N, P and K nutrients per wheat plant.     

Nitrogen immobilization by rice straw incorporated in lowland rice production

Summary The nitrogen supplying power of rice straw for flooded rice production was studied in three field experiments. The net nitrogen immobilization was observed to be 0.54 per cent of the original dry weight of the straw as determined by grain yield responses over single growing seasons. Straws with higher nitrogen concentrations increased grain yield on nitrogen deficient soil, and straws with lower nitrogen concentrations depressed yield.Supplemental nitrogen applied in either urea or vetch resulted in yield increases in the presence of both high and low nitrogen straws. No significant immobilization of supplemental nitrogen was found to result from straw applications.The net nitrogen immobilization percentage obtained in these experiments is approximately one-third the average of values obtained by other workers. We infer that the anaerobic environment of the flooded rice field and its associated bacterial microflora are the cause for the lesser nitrogen requirement for the field decomposition of rice crop residues.     

Studies on biological decomposition of wheat straw

Summary The incorporation of undecomposed wheat straw in the soil along-with the micro-organisms favourably increased the yield of groundnut crop. An increase of 37 per cent in yield was recorded when wheat straw was inoculated withPenicillium digitatum and the C:P ratio was adjusted to 65. Inoculated treatments of narrower C:P ratio gave a higher yield than wider C:P ratio treatments inoculated with the same cultures. An increase in nitrogen uptake by groundnut plants was recorded due to incorporation of straw alongwith the micro-organisms in soil. The organic carbon and nitrogen content of the soil increased with all the treatments except control. The highest increase in organic carbon and nitrogen of the soil was observed with a treatment of wheat straw of 65 C:P ratio inoculated withS. coccosporum. The yield of wheat crop after groundnut was significantly more with several treatments than control plots. The highest increase of 79 per cent in grain yield of wheat was observed in the plots previouslq received with wheat straw of 200 C:P ratio.This paper is based on the data presented at IV Southern Regional Conference on Microbial Inoculants, held at Parbhani during 3–4 July 1978.     

Significance of<Emphasis Type="Italic">Herbaspirillum seropedicae</Emphasis> inoculation and/or straw amendment on growth and dinitrogen fixation of wheat using<Superscript>15</Superscript>N-dilution method

The effect of Herbaspirillum seropedicae inoculation and/or maize straw (0, 5 and 10 Mg/hm2) amendment on the growth and N2 fixation of wheat was determined in pot experiments using 15N-dilution method. Inoculation resulted in accumulation of fixed nitrogen, and % N from atmosphere being 24.6 and 26.5% in wheat shoot and grain, respectively. Straw amendment reduced % Natm to 16.1 and 20.2% at high straw level (10 Mg/hm2). Rational nitrogen fertilization (180 kg N/hm2) completely inhibited N2 fixation by H. seropedicae inoculation. Bacterial inoculation increased dry shoot and grain yield up to 23 and 31%, respectively. The highest levels of shoot and grain dry mass (46.5 and 42.4%) were obtained by N-fertilization in both inoculated and uninoculated plants. Total shoot and grain N-yield increased irrespective of organic matter amendment by inoculation up to 9 and 25%, respectively. N-fertilized plants recorded a maximum increase in N-yield (57 and 51%). H. seropedicae was reisolated from inoculated wheat histosphere after harvesting (90 d from sowing). Neither organic matter nor mineral nitrogen applications had any marked effect on bacterial total counts colonizing wheat histosphere. Moreover, no symptoms of mottled stripe disease were observed on leaves and stems of inoculated plants.     

EFFECTS OF PREVIOUS WHEAT CROPS, SEED-RATE AND NITROGEN ON EYESPOT, TAKE-ALL, WEEDS AND YIELDS OF TWO VARIETIES OF WINTER WHEAT: FIELD EXPERIMENT 1954-56

In a replicated field experiment mean yields of wheat from plots that, in the preceding 2 years, had carried oats, beans or potatoes were 39.2 and 42.6 cwt. per acre in 1954 for Holdfast and Cappelle, respectively; 42.8 and 55.8 in 1955 and 34.9 and 49.6 in 1956. Previous wheat crops had more effect than any other treatment in increasing the incidence of eyespot, take-all and weeds and in decreasing the number of ears per unit area and the yield of grain. In 1956 on plots carrying the first, second and third successive wheat crops the percentages of straws with eyespot were respectively 12, 54 and 42 and with take-all 0.1, 1 and 16. Cappelle was less severely infected by eyespot than Holdfast. The second and third successive wheat crops yielded an average of 23.3 cwt./acre less than the first wheat crop. Cappelle consistently yielded more than Holdfast, the mean difference being 13.8 cwt./acre after potatoes but only 3.8 cwt./acre after two wheat crops. The higher seed-rate gave an average increase in grain yield of 3.3 cwt./acre; but where eyespot and take-all were both severe the lower seed-rate yielded as much total and more dressed grain than the higher. Wheat given a spring top dressing of 6 cwt./acre Nitro-Chalk yielded an average of 4 cwt./acre more grain than wheat given 3 cwt./acre.     

A greenhouse study on the effect of inoculation of N-fixing blue-green algae in an alluvial soil treated with P and Mo on the yield of rice and changes in the N-content of soil

Summary The efficiency of the inoculation of three cultures of N-fixing blue-green algaeviz. (i)Aulosira fertilissima (A₁), (ii)Nostoc muscorum (A₂) and (iii) their mixture (A₃) in increasing the grain and straw yield of rice, nitrogen uptake in grain and nitrogen content in soil was studied in a green house experiment with an alluvial soil in presence or absence of urea nitrogen application. Inoculation significantly increased the grain and straw yield of rice and nitrogen uptake in grain, but the efficiency of inoculation gradually decreased with the increase in the levels of urea nitrogen application, the extent of decrease varying with the algal cultures inoculated. The nitrogen content in the soils after the crop harvest recorded a significant increase due to inoculation but after air drying the soil a marker decrease of the same was observed, which indicated that most of the nitrogen added to the soil by blue-green algae through fixation did not persist after air drying the soil.     

Wheat bulb fly, Leptohylemyia coarctata Fall., and its effect on the growth and yield of wheat

In two experiments done in successive years to compare the growth and yield of Cappelle wheat either protected from or exposed to attacks by larvae of wheat bulb fly, the plots were previously fallowed, but egg laying was prevented on half of each plot by using Polythene soil covers. In the first season wheat was sown at the end of October, November and December and in the second season in late October and in early January, when there were two sowings, one with and one without a spring application of herbicide. The infestation rate was 1·1-1·7 million eggs per acre, typical of a moderate attack. Larvae had little effect on the yield of October-sown wheat as the plants had two shoots each when first attacked and few were killed. On plots sown late, yield was decreased by up to 22%, as plants had only a single shoot when attacked and many were killed. The main effect of wheat bulb fly was to reduce the number of ear-bearing shoots by killing plants and restricting the production of new shoots. Surviving plants partially compensated by producing more ear-bearing shoots with heavier ears and slightly heavier seeds than normal. Killed plants were not distributed uniformly but were often in patches several feet across. Wheat on the attacked plots ripened more slowly and unevenly than on the unattacked plots. Weather affects the growth of the plants and activity of the larvae and thus partly determines percentage shoot survival.     

Effect of Leaf Infection by Kabatiella zeae on Stalk Rot Prevalence and Grain Yield of Maize Hybrids

Eight maize hybrids were tested for resistance to eyespot (Kabatiella zeae) and stalk rot (Fusarium spp.) under field conditions in 1993–1995. The relationship between eyespot and stalk rot and their effect on grain yield of hybrids were studied. Effectiveness of the prochloraz fungicide in controlling both diseases was evaluated. The experiments were performed in three subtrials where plants were naturally infected, inoculated with K. zeae or treated with the fungicide, Sportak 450 EC. The relationship between intensity of leaf damage by eyespot and incidence of stalk rot has been evidently confirmed. High infection of leaf by K. zeae reduced grain yield of hybrids. However, considerable differences in prevalence of disease and yield losses were noted in successive years. The intensity of eyespot depended upon environmental conditions highly variable over the years: it was enhanced by low temperature and high air humidity in July and August. Hybrids showed significant differences in susceptibility to both diseases. Mona – hybrid from the USA and two experimental hybrids from Poland were less affected by diseases than Smolimag and Hidosil (commercial hybrids from Poland). The fungicide Sportak was effective in controlling eyespot and had an indirect influence on decreasing fusarium stalk rot.     

Effects of crop thinning and reduced grain numbers per ear on grain size in two winter wheat varieties given different amounts of nitrogen

To study the importance for final grain size in wheat (Triticum aestivum, L.) of assimilate supply and the storage capacity of the grain, two field experiments were done. In 1976 nitrogen was applied in the range from none to 180 kg ha^-1, part of the crop was thinned, and the top halves of some ears of the short variety Hobbit and of the tall variety Maris Huntsman were removed soon after anthesis. In 1977 ears of Maris Huntsman were halved 5 days after anthesis or at 30 days after anthesis when grain volume was maximum. Thinning the crop from 360 to 180 ear-bearing shoots m^-2 30 days before anthesis increased the number of grains per ear, except in the absence of nitrogen fertiliser, but did not increase grain size, grain dry weight per ear or total dry weight per culm. Removing the upper half of ears of Hobbit 5 days after anthesis increased dry weight per grain, but when this treatment was applied to Maris Huntsman either 5 days after anthesis in 1976 and 1977, or when grain volume was maximal in 1977, the grains failed to increase in dry weight. Non-grain dry weight of both varieties was increased by halving the ear. In both varieties the maximum volume of grains in halved ears was larger than in intact ears. Grain dry weight increased relatively less than volume after halving the ear of Hobbit, and the decrease in volume up to maturity was greater in halved than intact ears of both varieties. The larger grain volume in halved ears of Maris Huntsman in 1977 was associated with more endosperm cells.     

Soil and litter respiration rates in different microhabitats of a mixed oak-conifer forest and their control by edaphic conditions and substrate quality

Summary Seven isolates belonged toA. brasilense and 3 belonged toA. lipoferum. Isolates having more denitrifying capacity fixed less nitrogen in nitrogen free semi-solid malate medium. One strain ofA. lipoferum having high nitrogen fixing capacity with negative test for denitrification was tested as inoculant to supplement the nitrogen need of a wheat crop in field condition with different doses of N with and without the inoculant. While control without nitrogen yielded 1260 kg/ha the yield in inoculated treatment was 2070 kg/ha resulting in significant increase. In a treatment receiving 40 kg N/ha the grain yield was 2370 kg/ha as against yield of 3110 kg/ha in a similar treatment receiving fertiliser plus inoculant. Thus increase in yield was about 30%. Further the treatment receiving 80 kg N/ha yielded 2970 kg/ha as against yield of 4150 kg/ha in a treatment receiving inoculant alongwith the above dose of the fertiliser. Thus increase in yield due to application of inoculant was about 36%. Similarly, the uptake of N in different treatments was augmented due to inoculation of seeds with the culture.     

Intergenotypic competition and shoot production in wheat plants

In field experiments, the competition among plants of two distinct wheat genotypes in binary mixtures, and among three genotypes being grown in adjacent rows was investigated. The competition greatly affected the over-ground dry weight, weight of stem and grain per plant. This effect was undercompensatory, the depression in poor competitor was higher than the enhancement of strong competitor for all these characteristics. From final components of grain yield per plant, the number of fertile stems and number of grains per ear were more affected than weight per grain. More expressively than weight of grain on the main-stem ear, the weight of grain per average secondary ear-bearing stem was affected by competition in binary mixture. The enhancement in standard height—a strongly competitive genotype— reached in binary mixture about 10% for this last characteristic in comparison with the value from the pure stand. Some morphological characteristics of plants being in relation with competition for grain yield per plant are discussed in these experiments.     

Experiments with CCC on wheat: effects of spacing, nitrogen and irrigation

In experiments with spring and winter wheat at Rothamsted and Woburn during 4 years CCC increased yield at close spacing (4 in) (10 cm) more than at usual spacing (8 in) (20 cm), but there was no interaction between spacing and yield. Some experiments tested up to 2·4 cwt/acre (300 kg/ha) N to see whether yields continued to increase with more than usual amounts of N, when CCC prevented lodging. There was no evidence of this. When a short dry spell occurred at ear emergence, yield of spring wheat was increased by 6 cwt/acre (750 kg/ha) by CCC and 10 cwt (1250 kg) by irrigation. CCC probably improves yield in these conditions because the larger root system it causes enables more ear-bearing shoots to survive. CCC increases yield in two ways, either by increasing ears or grain per ear. In an unlodged crop CCC usually makes the grains smaller, but by preventing lodging it can also increase size. Usually CCC decreases the leaf area per shoot. The flag leaf may be smaller, unchanged or larger than those of untreated plants. There was no obvious connexion between flag-leaf area and grain yield; when CCC decreased flag-leaf area duration by 25 %, grain yield was unchanged. The results suggest that using CCC gives a more than even chance of a profitable yield increase.     

不同育秧方式和插植密度下早籼稻群体动态结构的研究

于1996年早季研究了湿润与旱育秧方式在稀植(2苗/科)和多植(4苗/科)情况下超高产早籼品种特三矮2号在本田生长期的群体动态结构与产量表现。与多植比较,稀植的比叶重较大,中期叶面积系数较小,每穗颖花数较多;但有效分蘖数较少。与湿润育秧比较,旱育秧每科穗数较多,抽穗后群体保持较高的叶面积系数和干物质生产力;但生育期较长。旱育稀植的谷草比较高。     

Short- and Long-eared High-yielding Hexaploid Wheat Cultivars: which has Unexpressed Potential for Higher Yield?

This investigation was designed to assess unexpressed potentialfor high yield and evaluate the sink strength of two high-yieldingwheat cultivars: a tall plant with long ears (LE), and a semi-dwarfwith short ears (SE). This was done by (1) removing one-thirdof the ear's distal end (decapitation), thereby inducing thedevelopment of additional florets, which usually do not form,on the untouched portion of the ear, and (2) by increasing thecompetition between the ears and the vegetative tissue's viathe application of gibberellic acid (GA). The number of grainsincreased on the untouched basal spikelets of the decapitatedears in both cultivars. The LE type fully recovered (100%) thenumber and mass of grains on the untouched portion of the decapitatedear. The decapitated SE type recovered 91% of the grain numberbut only 80% of individual grain mass. Thus, the total yield(number x mass) achieved by the untouched portion of the decapitatedear was 100% in the LE type and 80% in the SE type. Gibberelicacid treatment increased culm length in the tall LE plants butthis did not affect grain number of mass. Conversely, GA hadno significant effect on culm length of the semi-dwarf SE typebut significantly decreased their total grain yield. This effectwas due to a reduction in grain number by 64% of the control,rather than decreasing grain mass. Mean grain mass was not affectedby GA in either cultivar. A gradual increase in insoluble sugarconcentration (starch and fructan) in the ear peduncle duringthe first month after anthesis, followed by a sharp decreaselater, was found in the control and treated plants of both cultivars.In general, the concentrations of both soluble and insolublesugars declined as grain filling progressed, except for a noticeableincrease in total soluble sugars in the peduncles of the decapitatedears of the LE type. The results of this study suggest thatof the two high-yielding wheat cultivars that usually give identicalyields, the one with long multispikelet ears (LE) and lightergrains has significantly greater unexpressed potential for highyield than the cultivar with shorter ears (SE) and heavier grains.Copyright1995, 1999 Academic Press Ear, gibberellic acid, GA, grain number, grain mass, grain yield, sink strength, spikelet, Triticum aestivum, wheat     

EFFECT OF NITROGENOUS FERTILIZER APPLIED AT DIFFERENT DATES ON TAKE-ALL, EYESPOT AND YIELD OF WINTER WHEAT GROWN ON LIGHT SANDY LOAM

In a replicated field experiment on light sandy loam at Woburn, where winter wheat is a very uncertain crop, Cappelle and Holdfast, grown after potatoes with dung, yielded 50 and 41 cwt./acre of grain, respectively, when given 6 cwt./acre of Nitro-Chalk in April, compared with 19 and 20 cwt./acre when unfertilized. The same fertilized plots yielded 29 and 19 cwt., respectively, in the second, and 25 and 17 cwt./acre, respectively, in the third year on the same land, whereas unfertilized plots of both varieties yielded only 9 and 5 cwt./acre. The decrease in mean yield from 27 cwt. in the first, to 15 and 10 cwt./acre in the second and third crops was associated with a decrease in ear number from 16.7 to 14.6 and 12.2, respectively, and with a striking decrease in weight of grain per ear, caused partly by a large increase in the proportion of small grains. Eyespot ( Cercosporella herpotrichoides Fron.) although present each year did not become prevalent; an increase in the percentage straws affected by take-all ( Ophiobolus graminis Sacc.) from 9 to 15 and 26%, respectively, and a severe increase in weed infestation ( Agrostis gigantea ) appeared to be the main factors reducing yield.
Nitro-Chalk applied in April yielded most grain every year, and wheat fertilized at this time had less eyespot and take-all than that fertilized in March. Fertilizer applied in May increased weed growth, failed to decrease take-all and yielded fewer ears, less grain, and a higher proportion of tailcorn than did earlier applications.     

The effect of three or five years of set-aside on the husbandry and grain yield of subsequent cereal crops in the UK

During the period 1993–1997, at six contrasting sites located throughout England, two successive cereal test crops were grown both with and without nitrogen fertiliser after three or five years of set-aside or after continuous arable cropping. Vegetation during set-aside included natural regeneration and perennial rye-grass (Lolium perenne) with or without white clover (Trifolium repens), managed by mowing on one or more occasions per year. Establishment of the successive cereal test crops after destruction of the set-aside was generally not a problem. Fertile tiller numbers were increased by inclusion of clover in the set-aside cover or application of inorganic nitrogen. The presence of couch grass (Elytrigia repens) or volunteer cereals in the set-aside covers provided alternative hosts for take-all (Gaeumanomyces graminis) and eyespot (Pseudocercosporella herpotrichoides) and take-all caused some yield reductions in following cereal crops. Management during the set-aside period significantly affected grain yields of the subsequent cereal crops in the majority of the site-year combinations. However, these effects were not as large as would be expected after traditional break crops and were frequently masked by the application of nitrogen fertiliser. Mean yields increased by 80% due to the application nitrogen at the optimum rate compared to nil nitrogen. Most of the effects of set-aside treatment on grain yield were shown to be attributable to soil mineral nitrogen content, but at some sites, infections by take-all or eyespot also accounted for some of the variation. There were no effects of pests that could be related to treatment. The presence of sown clover during the set-aside period had the most consistent effect across sites, affecting tiller populations, grain yield and grain quality of cereal crops. At some sites, establishing a sown cover during the set-aside period, or cutting the cover more than once a year, improved grain yield and quality, and reduced the incidence of some specific weeds and disease. This revised version was published online in June 2006 with corrections to the Cover Date.     

Arbuscular mycorrhiza increased the activity of a biotrophic leaf pathogen – is a compensation possible?

Arbuscular mycorrhizal barley-plants were more susceptible to the obligate biotrophic shoot pathogen Erysiphe graminis f. sp. hordei. In experiments under greenhouse and open-air conditions on leaves of mycorrhizal plants, the sporulation rate of the mildew fungus was more than twice that on control plants. However, mycorrhizal plants suffered less than non-mycorrhizal plants in terms of grain number, ear yield and thousand-grain weight. Disease-yield-relationship analysis showed that the symbiosis neutralised the positive correlation between disease severity and yield loss (up to 25% infected leaf area tested). After mildew infection, nitrogen in ears of non-mycorrhizal barley was higher because of an impaired starch accumulation during grain filling. In mycorrhizal plants, leaf disease did not impair either the quantity or quality of grain yield. This improved compensation in mycorrhizal plants was related to maintained photosynthetic capacity and a delay in pathogen-induced senescence. Thus filling of long-term storage pools (fructans in internodes) and consequently reallocation of these reserves during grain filling was improved. The results suggest that higher availability of energy and material during grain formation, together with longer physiological activity, were the basis of yield maintenance and, therefore, expression of mycorrhiza-induced tolerance towards the pathogen.     

Constitutive expression of cell wall invertase genes increases grain yield and starch content in maize

Grain size, number and starch content are important determinants of grain yield and quality. One of the most important biological processes that determine these components is the carbon partitioning during the early grain filling, which requires the function of cell wall invertase. Here, we showed the constitutive expression of cell wall invertase–encoding gene from Arabidopsis, rice (Oryza sativa) or maize (Zea mays), driven by the cauliflower mosaic virus (CaMV) 35S promoter, all increased cell wall invertase activities in different tissues and organs, including leaves and developing seeds, and substantially improved grain yield up to 145.3% in transgenic maize plants as compared to the wild‐type plants, an effect that was reproduced in our 2‐year field trials at different locations. The dramatically increased grain yield is due to the enlarged ears with both enhanced grain size and grain number. Constitutive expression of the invertase‐encoding gene also increased total starch content up to 20% in the transgenic kernels. Our results suggest that cell wall invertase gene can be genetically engineered to improve both grain yield and grain quality in crop plants.