Improved persistence of red clover (Trifolium pratense L.) increases the protein supplied by red clover/grass swards grown over four harvest years

UK livestock agriculture can significantly reduce its protein imports by increasing the amount of forage based protein grown on-farm. Forage legumes such as red clover (Trifolium pratense L.) produce high dry matter yields of quality forage but currently available varieties lack persistence, particularly under grazing. To assess the impact of red clover persistence on protein yield, diploid red clover populations selected for improved persistence were compared with a range of commercially available varieties. All populations were grown over four harvest years in mixed swards with either perennial ryegrass (Lolium perenne L.) or perennial plus hybrid ryegrass (L. boucheanum Kunth). Red clover and total sward dry matter (DM) herbage yields were measured in Years 1–4, red clover plant survival in Years 3 and 4 and herbage protein (CP) yield and concentration in Years 2 and 4. In general, red clover DM yield in year 4 (3.4 t ha⁻¹) was lower than in year 1 (13.9 t ha⁻¹) but the red clover populations differed in the extent of this decline. Differences in the persistence of the red clover populations in terms of plant survival and yield were reflected in the contribution of red clover to the total sward yield in Year 4, which ranged from 61% for the highest yielding population, AberClaret, to 11% in the lowest yielding, Vivi. Increased red clover DM yield was reflected in a greater CP yield (protein weight per unit area), which ranged from 1.6 t ha⁻¹ year⁻¹ to 2.9 t ha⁻¹ year⁻¹ in Year 2 and from 1.1 t ha⁻¹ year⁻¹ to 1.9 t ha⁻¹ year⁻¹ in Year 4. CP concentration (protein weight per unit herbage weight) of all of the red clover populations was within a range considered suitable for ruminant production. The implication of these results for the future use of red clover in sustainable grassland systems is discussed.     

Effect of temperature and precipitation on nitrate leaching from organic cereal cropping systems in Denmark

The effect of variation in seasonal temperature and precipitation on soil water nitrate (NO₃N) concentration and leaching from winter and spring cereals cropping systems was investigated over three consecutive four-year crop rotation cycles from 1997 to 2008 in an organic farming crop rotation experiment in Denmark. Three experimental sites, varying in climate and soil type from coarse sand to sandy loam, were investigated. The experiment included experimental treatments with different rotations, manure rate and cover crop, and soil nitrate concentrations was monitored using suction cups. The effects of climate, soil and management were examined in a linear mixed model, and only parameters with significant effect (P < 0.05) were included in the final model. The model explained 61% and 47% of the variation in the square root transform of flow-weighted annual NO₃N concentration for winter and spring cereals, respectively, and 68% and 77% of the variation in the square root transform of annual NO₃N leaching for winter and spring cereals, respectively. Nitrate concentration and leaching were shown to be site specific and driven by climatic factors and crop management. There were significant effects on annual N concentration and NO₃N leaching of location, rotation, previous crop and crop cover during autumn and winter. The relative effects of temperature and precipitation differed between seasons and cropping systems. A sensitivity analysis revealed that the predicted N concentration and leaching increased with increases in temperature and precipitation.     

Effect of nitrogen fertilization on nitrate leaching in relation to grain yield response on loamy sand in Sweden

High rates of nitrogen (N) fertilizer may increase N leaching with drainage, especially when there is no further crop response. It is often discussed whether leaching is affected only at levels that no longer give an economic return, or whether reducing fertilization below the economic optimum could reduce leaching further. To study nitrate leaching with different fertilizer N rates (0–135 kg N ha⁻¹) and grain yield responses, field experiments in spring oats were conducted in 2007, 2008 and 2009 on loamy sand in south-west Sweden. Nitrate leaching was determined from nitrate concentrations in soil water sampled with ceramic suction cups and measured discharge at a nearby measuring station. The results showed that nitrate leaching per kg grain produced had its minimum around the economic optimum, here defined as the fertilization level where each extra kg of fertilizer N resulted in a 10 kg increase in grain yield (85% DM). There were no statistically significant differences in leaching between treatments fertilized below this level. However, N leaching was significantly elevated in some of the treatments with higher fertilization rates and the increase in nitrate leaching from increased N fertilization could be described with an exponential function. According to this function, the increase was <0.04 kg kg⁻¹ fertilizer N at and below the economic optimum. Above this fertilization level, the nitrate leaching response gradually increased as the yield response ceased and the increase amounted to 0.1 and 0.5 kg kg⁻¹ when the economic optimum was exceeded by 35 and 100 kg N ha⁻¹, respectively. The economic optimum fertilization level depends on the price relationship between grain and fertilizer, which in Sweden can vary between 5:1 and 15:1. In other words, precision fertilization that provides no more or no less than a 10 kg increase in grain yield per kg extra N fertilizer can be optimal for both crop profitability and the environment. To predict this level already at fertilization is a great challenge, and it could be argued that rates should be kept down further to ensure that they are not exceeded due to overestimation of the optimum rate. However, the development of precision agriculture with new tools for prediction may reduce this risk.     

Biological nitrogen fixation in a grazed perennial grass/clover ley and correlation with herbage and soil variables

In a grazed grass/clover pasture, biological nitrogen fixation (BNF) is a source of nitrogen (N). The determination of this N input and how it is influenced by N, phosphorus (P) and potassium (K) in the soil, is complicated by grazing animals, which cause variation in defoliation and soil mineral content in both space and time. In a perennial grass/clover ley on a commercial Danish organic farm, exclusively grazed by dairy cows, we investigated BNF, clover proportion of the herbage, accumulated dry matter of clover and N, P and K concentrations in separates of clover and grass in relation to inorganic concentrations of N, P and K in the soil. The ¹⁵N natural abundance technique was used to determine the proportion of clover N derived from the atmosphere (pNdfa) using grass as a non-fixing reference. In September 1997, soil and biomass sampling was carried out on 81 randomly selected plots. The value of pNdfa was on average 0.6, ranging from 0.12 to 0.96 and BNF exhibited a significant but weak correlation (r=0.432) with accumulation of dry matter in clover. For the significant correlations, r varied between −0.403 and 0.648. The proportion of clover in the sampled herbage averaged 48%, ranging between 18 and 78%, but varied independently of BNF. Due to a high concentration of P and moderate to high concentration of K in the soil, clover and grass were well supplied with P and K, which was confirmed by the concentrations of K and P in shoot material.     

Effects of species diversity on seasonal variation in herbage yield and nutritive value of seven binary grass-legume mixtures and pure grass under cutting

Intensively managed sown temperate grasslands are generally of low species diversity, although swards based on grass-legume mixtures may have superior productivity and herbage quality than grass-only swards. We conducted a cutting experiment over two years to test the effect of species composition and diversity on herbage yield, contents of N, neutral detergent fibre (NDF) and in vitro organic matter digestibility (IVOMD). Perennial ryegrass (PR, Lolium perenne) was sown alone and with each of four forage legumes: red clover (RC, Trifolium pratense), lucerne (LU, Medicago sativa), birdsfoot trefoil (BT, Lotus corniculatus) and white clover (WC, Trifolium repens); WC was also sown with hybrid ryegrass (HR, Lolium × boucheanum), meadow fescue (MF, Festuca pratensis) and timothy (TI, Phleum pratense). Herbage productivity was lowest in pure PR followed by PR/BT, and highest in PR/RC; this mixture had the highest legume proportion, N content and N yield. There was less WC in swards with HR and MF than with PR and TI. These differences were reflected in N contents of herbage of the mixtures. Legumes had higher N and lignin and lower NDF contents and IVOMD than grasses. Among legumes, NDF content was highest and IVOMD lowest in LU, followed by BT and the clovers. The highest N content was in WC. Among grasses, PR and HR had lower NDF contents and a higher IVOMD than MF; the highest N content was in PR. The grass component of mixtures had less effect than the legume component on herbage yield and quality. Results are discussed in terms of their potential to contribute to forage resources in farming practice and enhance resource use efficiency and ecosystem services.     

Estimation of the year-to-year variations in nitrate leaching in different soils and regions of England and Wales

A model has been used to estimate the losses of N by leaching from arable soils throughout England and Wales during winter and spring. It is predicted that the extent to which autumn residues of nitrate are leached by winter rains varies considerably from year to year and from site to site, and that this variation will cause much bigger differences in the N fertilizer requirements of deep-rooted crops than of shallow-rooted ones. It is estimated that an average of about 42% of the N applied as fertilizer is leached from arable soils in England and Wales each year. However, the resulting increase in the average nitrate concentration in the drainage water is estimated to exceed 11.3 μg N/ml only in the Eastern region. Spring leaching of freshly-applied N fertilizer is likely to be generally small, and will have little effect on the N fertilizer requirements of deep-rooted crops, but may affect those of shallow-rooted crops in the west.     

Mechanical control of clover improves nitrogen supply and growth of wheat in winter wheat/white clover intercropping

The major objective for clover in a winter wheat/white clover intercropping system is to supply nitrogen (N) for the wheat. A field experiment was repeated in 2 years on a loamy sand in Denmark to investigate the possibilities for increasing N supply to the winter wheat by cutting and mulching the clover between the wheat rows. The clover was cut with a weed brusher on three different dates in each year.Intercropped wheat with unbrushed clover had a lower grain yield than wheat as a sole crop. Brushing increased wheat N uptake and wheat grain yields. Intercropping with two or three brushing dates gave higher wheat yields than wheat as the sole crop. The largest increases in grain N uptake, 21–25 kg N ha⁻¹, were obtained for the brushings around wheat flag leaf emergence. The highest yield increases with a single brushing, 0.98–1.11 Mg DM ha⁻¹, were obtained when brushing was performed during the stem elongation phase. The largest grain yields for treatments with two brushings were obtained with a first brushing at start of stem elongation and a second around flag leaf emergence. The first brushing probably provided N to increase the wheat leaf area index and thus the light interception, while the second brushing provided N to sustain the leaf area during grain filling and reduced clover biomass and therefore competition for water. Intercropping wheat and clover increased grain N concentrations by 0.11–0.39%-point compared with wheat as a sole crop. Intercropping may thus offer possibilities for improving the bread-making quality of organically grown wheat.     

Effect of spring fertilization on ecosystem services of organic wheat and clover relay intercrops

Nitrogen (N) deficiency and weed infestation are main factors limiting yield and yield stability in organic wheat. Organic fertilizers may be used to improve crop performance but off-farm input costs tend to limit profitability. Instead, forage legumes may be inserted into the crop rotation to improve the N balance and to control weed infestation. In opposition to simultaneous cropping, relay intercropping of legumes in organic winter wheat limits resource competition for the legume cover crop, without decreasing the performance of the associated wheat.The aim of this study is to evaluate the effect of spring organic fertilization on the performance of intercropped legumes and wheat, and on services provided by the legume cover.Two species of forage legumes (Trifolium pratense L. and Trifolium repens L.) were undersown in winter wheat (Triticum aestivum L. cv Lona) in five organic fields during two consecutive crop seasons. Organic fertilizer was composed of feather meal and applied on wheat at legume sowing. The cover crop was maintained after the wheat harvest and destroyed just before sowing maize.Spring organic nitrogen fertilization increased wheat biomass (+35%), nitrogen (+49%), grain yield (+40%) and protein content (+7%) whatever the intercropping treatment. At wheat harvest, red clover biomass was significantly higher than white clover one (1.4 vs. 0.7 t ha⁻¹). Nitrogen fertilization decreased forage legume above-ground biomass at wheat harvest, at approximately 0.5 t ha⁻¹ whatever the specie. No significant difference in forage legume biomass production was observed at cover killing. Nitrogen accumulation in legume above-ground tissues was significantly higher for white clover than for red clover. Both red and white clover species significantly decreased weed infestation at this date. Nitrogen fertilization significantly increased weed biomass whatever the intercropping treatment and decreased nitrogen accumulation in both clover species (−12%).We demonstrated that nitrogen fertilization increased yield of wheat intercropped with forage legume while the performance of legumes was decreased. Legume growth was modified by spring fertilization whatever the species.     

硼锰钼配施对紫花苜蓿草产量和矿物质元素吸收的影响

采用叶面喷施的方法,研究了硼锰钼配施对紫花苜蓿草产量和矿质元素含量及产量的影响。结果表明：硼锰钼配施可以提高紫花苜蓿干草产量,其中以单施钼产量最高,硼钼配施次之,与CK处理相比分别增产约54.75%、40.34%。硼锰钼不同配施对紫花苜蓿矿质元素含量及产量的影响不同,硼锰钼配施降低了苜蓿铁、锰、锌含量,其中以硼钼配施降低效果最显著;施微肥可以提高苜蓿铜含量,其中以硼锰钼配施效果最好;而硼锰、硼钼配施可分别显著提高硼、钼含量。硼锰钼配施提高了紫花苜蓿矿质元素产量,其中单施硼显著提高了苜蓿铁、锰、锌产量,单施钼、硼锰、硼钼配施分别显著提高了苜蓿铜、硼、钼产量。     

Optimising crop production and nitrate leaching in China: Measured and simulated effects of straw incorporation and nitrogen fertilisation

The sustainability of growing a maize—winter wheat double crop rotation in the North China Plain (NCP) has been questioned due to its high nitrogen (N) fertiliser use and low N use efficiency. This paper presents field data and evaluation and application of the soil–vegetation–atmosphere transfer model Daisy for estimating crop production and nitrate leaching from silty loam fields in the NCP. The main objectives were to: i) calibrate and validate Daisy for the NCP pedo-climate and field management conditions, and ii) use the calibrated model and the field data in a multi-response analyses to optimise the N fertiliser rate for maize and winter wheat under different field managements including straw incorporation.The model sensitivity analysis indicated that a few measurable crop parameters impact the simulated yield, while most of the studied topsoil parameters affect the simulated nitrate leaching. The model evaluation was overall satisfactory, with root mean squared residuals (RMSR) for simulated aboveground biomass and nitrogen content at harvest, monthly evapotranspiration, annual drainage and nitrate leaching out of the root zone of, respectively, 0.9 Mg ha⁻¹, 20 kg N ha⁻¹, 30 mm, 10 mm and 10 kg N ha⁻¹ for the calibration, and 1.2 Mg ha⁻¹, 26 kg N ha⁻¹, 38 mm, 14 mm and 17 kg N ha⁻¹ for the validation. The values of mean absolute deviation, model efficiency and determination coefficient were also overall satisfactory, except for soil water dynamics, where the model was often found erratic. Re-validation run showed that the calibrated Daisy model was able to simulate long-term dynamics of crop grain yield and topsoil carbon content in a silty loam field in the NCP well, with respective RMSR of 1.7 and 1.6 Mg ha⁻¹. The analyses of the model and the field results showed that quadratic, Mitscherlich and linear-plateau statistical models may estimate different economic optimal N rates, underlining the importance of model choice for response analyses to avoid excess use of N fertiliser. The analyses further showed that an annual fertiliser rate of about 300 kg N ha⁻¹ (100 for maize and 200 for wheat) for the double crop rotation with straw incorporation is the most optimal in balancing crop production and nitrate leaching under the studied conditions, given the soil replenishment with N from straw mineralisation, atmospheric deposition and residual fertiliser.This work provides a sound reference for determining N fertiliser rates that are agro-environmentally optimal for similar and other cropping systems and regions in China and extends the application of the Daisy model to the analyses of complex agro-ecosystems and management practices under semi-arid climate.     

Effect of inbreeding on pseudo-self-compatibility in red clover (Trifolium pratense L.)

Summary The effect of inbreeding on pseudo-self-compatibility (PSC) was investigated in I₀, I₁, and I₂ clones of red clover, Trifolium pratense L., at 40°C. PSC was found to decrease with inbreeding. Significant differences were found among I₀ clones, among I₁ clones, and among I₂ clones for PSC. Significant differences in PSC within generations were found in two of eight I₁ clones and one of five I₂ clones.A new method of inbred line maintenance is proposed which combines the desirable features of vegetative and seed maintenance of inbred lines. Superior I₁ clones with different but homozygous S genotypes and PSC values of 8 to 10% would be vegetatively increased. Clones would be isolated under high temperature field conditions and selfed seed (PSC) would produce the I₂. Selfed seed from two different I₁ clonal lines would then be mixed and sown to produce single-cross seed. Singlecross seed obtained from different clonal sources would be mixed and sown for the production of double-cross hybrid red clover.Contribution from the Kentucky Agricultural Experiment Station. This paper (72-3-125) is published with approval of the Director, Kentucky Agricultural Experiment Station, Lexington.     

Morphological characteristics of hybrids between white clover, Trifolium repens L., and Caucasian clover, Trifolium ambiguum M. Bieb

Hybrids between the stoloniferous Trifolium repens (2n = 4x = 32) and the rhizomatous Trifolium ambiguum (2n = 4x = 32) have been produced using T. repens as the recurrent parent. Morphological characteristics of the parent species and the F₁, BC1, BC2 and BC3 hybrids were examined in a glasshouse experiment. Leaflet ratios and general plant shape indicated that the BC3 hybrid was similar to T. repens. Separation of plants into components of above- and below-ground growth showed that T. repens had a greater total plant dry weight than T. ambiguum but 24% of its dry weight was in roots compared with 22% in roots and 44% in rhizomes in T. ambiguum. The BC3 generation contained plants that were predominantly T. repens-like with stolons, but also had a small proportion of their total dry weight (3%) as rhizome, confirming the potential to produce plants that combine stoloniferous and rhizomatous growth. The proportions of rhizome and stolon varied within the BC3 generation, enabling farther selection and plant breeding. The BC3 hybrids produced similar numbers of inflorescences to T. repens however, fertility was lower, although there was some variation within the BC3 for both characters.     

Root traits of cup plant,maize and lucerne grass grown under different soil and soil moisture conditions

The cup plant (Silphium perfoliatum L.) is presently discussed as a promising alternative to silage maize for biomethane production in Germany. It is assumed that the cup plant develops a profound root system, contributing decisively to the drought tolerance of this crop. This study is aimed at providing the first experimental data on root growth and water uptake of this novel biogas crop. Root morphological characteristics of the cup plant were studied at six sites differing in soil type. Root samplings were made at the time of maximum root expansion (flowering). In a 2‐year field experiment at an additional location, continuous measurements of root development and soil water acquisition during the growth cycle were taken under contrasting water supply, together with maize (Zea mays L.) and lucerne grass (mixture of Medicago sativa L. with Festuca pratensis Huds. and Phleum pratense L.) as reference crops. The cup plant attained maximum rooting depths of 80–240 cm. The root length density was comparable to that of maize, but markedly lower than that of lucerne grass. Despite the cup plant's higher potential evapotranspiration and similar water‐use efficiency, its soil water extraction ability was significantly lower than that of lucerne grass. Compared with maize and lucerne grass, the cup plant showed no outstanding ability to cope with drought stress by means of its root system. Because of its high potential evapotranspiration, the cup plant can attain biomass yields comparable to those of maize only at sites with high water supply.     

Structure and variation of subterranean clover populations from Sicily,Italy

Summary A collection of subterranean clover lines singled out from populations of the species Trifolium brachycalycinum and T. subterraneum collected in Sicily, Italy, was examined at two localities for flowering time and at one locality for oestrogen content and seed yield. The structure and variation of the populations of the two species were compared. The relationship between flowering time of the populations and some environmental features of their collection sites was examined to assess whether the maturity requirements of the two species were similar and to frame selection models focused on developing varieties of appropriate maturity. Populations of T. subterraneum were, on average, more complex than those of T. brachycalycinum, being characterized by higher number of lines per population and greater intra-population variation for flowering time, oestrogen content and seed yield. Furthermore, populations of T. subterraneum were, on average, about 15 days earlier than sympatric populations of T. brachycalycinum. Both the greater variation and the relative earliness of T. subterraneum occurred irrespective of the environments of origin of the populations. Inferences are drawn on the adaptive advantages that such features confer to T. subterraneum. Mean flowering time of the populations increased on increasing annual rainfall and altitude of the collection sites. However, the changes in maturity appeared almost exclusively related to variations in rainfall in T. subterraneum, while in T. brachycalycinum the effect of altitude was greater and that of rainfall less marked than in the former species.     

Effects of harvest management on growth dynamics, forage and seed yield in berseem clover

Berseem clover (Trifolium alexandrinum L.) is an annual forage crop widely grown in Mediterranean environments. However, there is little information available on the patterns of accumulation and partitioning of assimilate in berseem and how this varies with harvest management, plant ontogeny or is influenced by genotype. Field experiments were conducted in Foggia (Italy) during three growing seasons (1991–92, 1992–93 and 1993–94), with the aim of evaluating the effects of different harvest managements on growth dynamics, forage yield and seed yield of one population of Egyptian (cv. ‘Giza 10’) as well as Italian (cv. ‘Sacromonte’) origin. Cutting treatments were applied at three different plant ages: sixth internode elongation (A), early flowering (B), and uncut control (C). The growth and development of the shoot and root systems were followed by destructive harvests made at about 5-day intervals during 9 weeks in spring in all treatments. Seasonal growth pattern, determined as dry matter accumulation, forage yield and seed production were greatly influenced by harvest management. The maximum value (20.5 g per plant on average) of dry weight was reached at about 250 days after sowing for treatment C. Defoliation induced a decrease of crown and root dry matter, however, as shown by the allometric relationships, the growth of roots and shoots was closely correlated and in most cases, shoot growth was higher than root growth and stem relative growth rate (RGR) was higher than leaf RGR. Berseem clover is a defoliation-tolerant species because after cutting, regrowth was accompanied by higher values of leaf-stem ratio (LSR), RGR and stem elongation rate (SER) than in control plants. The highest value for total forage yield (1.6 Kg m⁻²) and seed yield (60.5 g m⁻²) were obtained in treatment B and A, respectively. Plants cut at the sixth internode elongation showed a good seed yield and a small decrease (15%) in total forage yield as regards treatment B. Therefore, treatment A appeared the most favourable for obtaining double utilization (forage and seed yield) in a berseem crop. Berseem plants were greatly influenced by harvest treatments applied, but the response did not vary according to the genetic characteristics of the two cultivars examined.     

Effects of biogas digestion of clover/grass-leys, cover crops and crop residues on nitrogen cycle and crop yield in organic stockless farming systems

The trend towards specialization in conventional farming led to large agricultural areas in Germany and in Europe lacking livestock. Also stockless organic farming has increased during recent years. In organic farming clover/grass-ley (CG) provides nitrogen (N) to the whole cropping system via symbiotic N₂ fixation and also controls certain weeds. A common practice in organic farming, when ruminants are not present, is to leave the biomass from CG in the field for their residual fertility effect. CG biomass, crop residues (CR) and cover crops (CC) represent a large unexploited energy potential. It could be used by anaerobic digestion to produce biogas. A field experiment was carried out by implementing a whole cropping system with a typical crop rotation for such farming systems on the research station Gladbacherhof from 2002 to 2005. The crop rotation consisted of six crops (two legumes and four non-legume crops). The aim was to evaluate whether the use of N could be improved by processing biomass from CG, CR and CC in a biogas digester and using the effluents as a fertilizer, compared to common practice. In the control treatment, represented by the usual stockless system, the CG, CR and CC biomass were left on the ground for green manure purposes. In the biogas systems these substrates were harvested for digestion in a biogas plant. The effluents of digestion were used to manure the non-legumes in the same crop rotation. Results indicate that digestion of CG, CR and CC can increase the crop dry matter and N yields and the N content of wheat grains in organic stockless systems. Harvesting and digestion of residues and their reallocation after digestion resulted in a better and more even allocation of N within the whole crop rotation, in a higher N input via N₂ fixation and lower N losses due to emissions and probably in a higher N availability of digested manures in comparison to the same amounts of undigested biomass.     

Effect of Gluconacetobacter diazotrophicus and Trichoderma viride on soil health, yield and N-economy of sugarcane cultivation under subtropical climatic conditions of India

Intensive cropping and exhaustive nature of sugarcane–wheat–rice cropping system in the Indo-Gangetic Plains of South Asia have led to the depletion of soil organic carbon content and inherent soil fertility resulting in a serious threat to the sustainability of these production systems. Bioagents like Gluconacetobacter diazotrophicus and Trichoderma viride have great potential to restore soil fertility and promote sugarcane growth. Field experiments, therefore, have been conducted to study the integrated effect of bioagents (G. diazotrophicus and T. viride), Farm Yard Manure (FYM) and fertilizer N on sugarcane rhizosphere, crop yield and N economy for two crop cycles during 2004–2006 and 2005–2007 crop seasons at Lucknow, in the middle Indo-Gangetic plain region. Both bioagents could survive and colonize sugarcane rhizosphere and FYM improved their colonization. Enhanced soil microbial population and microbial carbon (SMC) and nitrogen (SMN) with increasing N level were probably due to more available N in the soil. FYM/bioagents amendment further enhanced the microbial carbon. The uniform increase in the fraction of SMC and SMN of total organic carbon indicated that immobilization/mineralization was being maintained in the soil where enhanced microbial biomass might act later as a source of nutrients.Bioagents ammended FYM enhanced the uptake of N, P and K in sugarcane at all the levels of fertilizer N. It was mainly due to the enhanced nutrient availability in the rhizospheric soil as the soil organic C and available N, P and K content increased with the application of bioagents/FYM. A saving of 76.3 kg N ha⁻¹ was envisaged by the use of G. diazotrophicus inoculated FYM with marginal (2.4 t ha⁻¹) decline in the cane yield. Application of T. viride enriched FYM, however, brought economy in the use of fertilizer N by 45.2 kg ha⁻¹ and also increased the yield by 6.1 t ha⁻¹compared to the control treatment. Overall, strategic planning in terms of an integrated application of these bioagents/manures with fertilizer N will not only sustain soil fertility but will also benefit farmers in terms of reducing their dependence and expenditure on chemical fertilizers.     

不同钙化剂对高钒渣酸浸提钒的影响

针对传统钒渣钠化焙烧-水浸提钒工艺的不足,确定对钒渣钙化焙烧-酸浸提钒进行研究。在理论分析的基础上,本研究以高钒渣为原料,研究了钙化焙烧-酸浸提钒过程中3种钙化剂(CaSO4、CaCO3、CaO)的焙烧机理以及对提钒效果的影响。研究结果表明：钒浸出率随焙烧温度的升高先增大后减小,且在1 450 K时达到最大值;钙化剂配比为100%CaSO4时提钒率最大;在目前实验室研究条件下,钒的浸出率最大可达93.53%。     

Heritability of, and genetic correlations among, forage and seed yield traits in Ladino white clover

Sixteen white clover genotypes and their half-sib progenies were grown in pure stand. Each clover progeny was also grown in a mixed stand that also included three grass varieties of different species. Dry matter (DM) yield was measured over 2 years and seed yield at the second year. Competitive ability of clover families was defined as the ratio between mixed stand and pure stand for clover DM yield. Narrow-sense heritability from parent-offspring regression of pure stand data was high to moderate (h²0.50) for DM yield, seed yield and most of their components. Persistence as predicted by stolon density showed negative genetic correlations with seed yield (r_g= -0.70) and DM yield (r₂= -0.60), whereas seed yield and DM yield tended towards a negative correlation (r₂=0.45). Sizes of different vegetative or reproductive organs were generally correlated positively. Evidence was provided that the set of parent genotypes represents well the genetic variation available within the Ladino gene pool. The results highlighted the difficulty of combining relatively short-term DM yield, persistence and seed yield into a unique plant type. Differences in competitive ability emerged only in the second year, better ability being related mainly to petiole length among the traits assessed in pure stand.