Sugarcane by-products used as soil amendments on a sandy soil: Effects on sugarcane crop nutrition and yield

Agricultural by-products applied as soil amendments have the potential to improve crop production on low organic matter (OM) soils. This two-year study investigated the use of two readily available sugarcane (Saccharum spp.) milling by-products, mill mud, and mill ash, as soil amendments to improve first sugarcane crop (plant cane) and subsequent crop (first ratoon) grown on a sandy Spodosol. Sugarcane was grown in lysimeters receiving mill mud, mill ash, and a 50:50 (v:v) mill mud to mill ash mix. Amendments were applied at low, medium, and high application rates (5, 10, and 15 cm depths, respectively) and then incorporated 30 cm deep. Amendment effects on plant nutrition, soil characteristics, and crop yield were determined. High rate applied mill mud and mill ash had the highest soil OM content for both years and soil OM did not significantly change between crops for all treatments except for high rate mill mud, which increased the second year (ratoon crop). Leaf nutrient levels for nitrogen (N), iron (Fe), and copper (Cu) for all treatments both years were insufficient; nutrient levels for magnesium (Mg), manganese (Mn), and silicon (Si) were within marginal to sufficient range for all treatments both years. All amendments produced significantly higher biomass and sucrose yields for plant cane and first ratoon crops compared to the control. Mill ash treatments produced the greatest increase in sucrose and biomass yields from plant cane to ratoon crops, which corresponded with an increase in potassium (K) in leaf tissue. However, mid and high rates of mix produced the highest sugarcane biomass and sucrose yields for the both the plant cane and ratoon crops.     

Establishment techniques in under-sown perennial ryegrass for seed production

Abstract

Establishment methods have proven to be of major importance for grass-seed production. The objective of this research was to test the effect of different sowing techniques on plant establishment and the subsequent seed yield. Perennial ryegrass (Lolium perenne L.) is used as the model grass due to its large importance in Danish agriculture.

In a three-year trial six different methods of under-sowing of perennial ryegrass in a spring barley cover crop were employed. Perennial ryegrass was either sown directly at different depths within the spring barley (Hordeum vulgare L.) rows or placed 2, 6, or 12 cm from the spring barley rows. Results of dry-matter yield indicate that the best establishment of the grass occurred when placing the grass 6 or 12 cm from the cover-crop row, and this is of importance in less vigorous grasses. Overall, no seed-yield difference has been observed for perennial ryegrass when placing the grass 2, 6, or 12 cm from the cover-crop row. Placement of the ryegrass seed crop 6 cm from the cereal row showed that a significant yield increase of 34–71 kg ha^?1 can be obtained compared with sowing in the cereal row.     

Vegetative Waste Management on Sugarcane Yield and Industrial Quality

Sugarcane (Saccharum officinarum L.) has economic importance in tropical and/or subtropical regions, because of the high sucrose content for cost-effective sugar and ethanol production. The aim of this study was to evaluate the impact of vegetative waste on crop yield and industrial quality of the sugarcane. The experiment was carried out in a Kaolinitic Typic Eutrorthox, loamy texture, using the following six treatments: no fire, but leaving 0, 5, 10, 15, and 20 Mg ha^?1 of straw mulch without trash incorporation, and sugarcane with burning and manual cutting before the harvesting, with four replicates. We evaluated total stalk yield (TSY) and industrial quality based on the apparent sucrose contents in the stalks (Pol), fibers, apparent purity (AP), reducing sugar (RS), and total recoverable sugar (TRS). The TSY after harvest, industrial quality at 180 and 240 days after harvest (DAH) and at the pre-harvest (350 days DAH) were also evaluated. The vegetative wastes had no influence in industrial quality, but 10 and 15 Mg ha^?1 provided TSY 32% higher than the burning and manual cutting and 0 and the 5 Mg ha^?1 of straw mulch. The use of 50% of waste to produce energy in sugarcane industrial plant did not reduce crop yield or industrial quality.     

Rapid,Wet Oxidation Procedure for the Estimation of Silicon in Plant Tissue

Abstract

The quantification of silicon (Si) in plant samples is being requested more frequently, especially in agricultural laboratories associated with the determination of nutritional requirements of sugarcane (Saccharum officinarum L.) and rice (Oryza sativa L.). The analysis of plant material for Si can be protracted, especially if laboratories do not have access to X‐ray flourescence (XRF) instrumentation and large numbers of samples are involved. A simplified procedure using equipment considered standard in most agricultural laboratories is reported. Dry, ground plant material is subjected to nitric acid/peroxide oxidation in a low‐pressure laboratory microwave digestion system. The hydrated silica liberated from the organic matrix is dissolved in a small volume of sodium hydroxide solution also using the microwave digestion system. Silicon is measured by inductively coupled plasma atomic emission spectrometry (ICP‐AES). This method gives results that are linearly correlated with the much slower conventional techniques and avoids using hazardous chemicals (hydrofluoric acid) sometimes employed in other microwave methods.     

SUGARCANE NUTRITIONAL DIAGNOSIS WITH DRIS NORMS ESTABLISHED IN BRAZIL,SOUTH AFRICA,AND THE UNITED STATES

ABSTRACT

The Diagnosis and Recommendation Integrated System (DRIS) approach evaluates plant nutritional status. The Diagnosis and Recommendation Integrated System is based on a comparison of crop nutrient ratios with optimum values from a high-yielding group (DRIS norms). Several researchers affirm that once DRIS norms based on foliar composition have been developed for a given crop, they are universal and applicable to that particular crop grown at any place and at any stage of its development. But different diagnoses with DRIS norms established for the same crop but under different growth conditions have been found. The objectives of this study were (i) to evaluate the confidence intervals of three DRIS norms of sugarcane crop, (ii) to compare sugarcane nutritional diagnosis with three DRIS norms, and (iii) to evaluate the universal use of DRIS norms in sugarcane crop. Sugarcane DRIS norms were tested. Means for nitrogen (N)/phosphorus (P), N/calcium (Ca), N/copper (Cu), manganese (Mn)/N, N/zinc (Zn), Ca/P, Cu/P, Mn/P, Zn/P, potassium (K)/Ca, K/Cu, Mn/K, Zn/K, Mn/Ca, Zn/Ca, Cu/magnesium (Mg), Mn/Mg, Zn/Mg, Mn/Cu, Zn/Cu, and Zn/Mn of these three DRIS norms were significantly different (?p<0.05). The sugarcane nutritional diagnosis derived from norms published in the literature was different. These three DRIS norms were not universally applicable to the sugarcane crop. Therefore, in the absence of DRIS norms locally calibrated, norms developed under one set of conditions only should be applied to another if the nutrient concentrations of high-yielding plants from these different set of conditions are similar.     

Characterization of intergeneric hybrids of <Emphasis Type="Italic">Erianthus rockii</Emphasis> and <Emphasis Type="Italic">Saccharum</Emphasis> using molecular markers

Erianthus rockii, a wild relative of sugarcane, is drought and cold tolerant, and both are potentially important agronomic traits to the sugarcane industry worldwide. As such it is of interest as a source of parental germplasm to sugarcane breeders and is currently being used in sugarcane introgression programs in both China and Australia. To date morphological characters have been used to verify the putative hybrids produced. Two crosses were generated between two different Saccharum species and two E. rockii accessions. Over 400 AFLP markers were used to identify the intergeneric hybrid progeny as well as determine hybrid diversity. Both crosses generated hybrids but efficiency levels were very different and are probably related to the different Saccharum parent used in each cross. Cross 1 was between a Saccharum officinarum and E. rockii and generated 100% hybrid progeny. Cross 2, however, was between a sugarcane hybrid (S. officinarum × Saccharum spontaneum) and E. rockii and only 10% of the progeny were intergeneric hybrids. Inheritance of markers in the progeny was analysed and for both crosses there were equal numbers of markers from both parents indicating n + n transmission of chromosomes. This is the first verification of E. rockii hybrids with molecular markers. It may now be possible to exploit genes of value from E. rockii in sugarcane breeding programs.     

土壤碳氮对多年生能源草、覆盖作物和氮施肥的响应

Cover crop and nitrogen(N) fertilization may maintain soil organic matter under bioenergy perennial grass where removal of aboveground biomass for feedstock to produce cellulosic ethanol can reduce soil quality. We evaluated the effects of cover crops and N fertilization rates on soil organic carbon(C)(SOC), total N(STN), ammonium N(NH_4-N), and nitrate N(NO_3-N) contents at the0–5, 5–15, and 15–30 cm depths under perennial bioenergy grass from 2010 to 2014 in the southeastern USA. Treatments included unbalanced combinations of perennial bioenergy grass, energy cane(Saccharum spontaneum L.) or elephant grass(Pennisetum purpureum Schumach.), cover crop, crimson clover(Trifolium incarnatum L.), and N fertilization rates(0, 100, and 200 kg N ha~(-1)). Cover crop biomass and C and N contents were greater in the treatment of energy cane with cover crop and 100 kg N ha~(-1) than in the treatment of energy cane and elephant grass. The SOC and STN contents at 0–5 and 5–15 cm were 9%–20% greater in the treatments of elephant grass with cover crop and with or without 100 kg N ha~(-1)than in most of the other treatments. The soil NO_3-N content at 0–5 cm was 31%–45% greater in the treatment of energy cane with cover crop and 100 kg N ha~(-1)than in most of the other treatments.The SOC sequestration increased from 0.1 to 1.0 Mg C ha~(-1)year~(-1)and the STN sequestration from 0.03 to 0.11 Mg N ha~(-1)year~(-1)from 2010 to 2014 for various treatments and depths. In contrast, the soil NH_4-N and NO_3-N contents varied among treatments,depths, and years. Soil C and N storages can be enriched and residual NO_3-N content can be reduced by using elephant grass with cover crop and with or without N fertilization at a moderate rate.     

Growth response of the salt-sensitive and the salt-tolerant sugarcane genotypes to potassium nutrition under salt stress

Adequate regulation of mineral nutrients plays a fundamental role in sustaining crop productivity and quality under salt stress. We investigated the ameliorative role of potassium (K as K₂SO₄) in overcoming the detrimental effects of sodium chloride (NaCl) on sugarcane genotypes differing in salt tolerance. Four levels of NaCl (0, 100, 130 and 160 mM) were imposed in triplicate on plants grown in gravel by supplying 0 and 3 mM K. The results revealed that application of NaCl significantly (p ≤ 0.05) increased sodium (Na⁺) but decreased K⁺ concentrations in shoots and roots of both genotypes with a resultant decrease in K⁺/Na⁺ ratios. Physical growth parameters and juice quality were also markedly reduced with increasing NaCl concentrations compared with controls. However, addition of K alleviated the deleterious effects of NaCl and improved plant growth under salt stress. Cane yield and yield attributes of both genotypes were significantly (p ≤ 0.05) higher where K was added. Juice quality was also significantly (p ≤ 0.05) improved with the application of K at various NaCl levels. The results suggested that added K interfered with Na⁺, reduced its uptake and accumulation in plant tissues and consequently improved plant growth and juice quality in sugarcane.     

Carbon input, loss and storage in sub-tropical Indian Inceptisol under multi-ratooning sugarcane

Changes in residue management and incorporation of organic manures may help in carbon sequestration, restoring soil organic carbon (SOC) and sustaining the productivity of land under a cropping system. An experiment of multi-ratooning sugarcane (Saccharum officinarum L.) was initiated in 2003 in Inceptisols of Indian subtropics, to assess the effect of different organic manures and chemical fertilizer, on the crop productivity and soil quality. The annual sugarcane shoot biomass production in organic manure treatments was at par with the chemically fertilized treatment. Gross input of carbon (GIC) by the sugarcane crop was estimated to be 11.7–12.4 t ha⁻¹ y⁻¹ in different organic manure treatments compared to 8.4 and 5.0 t ha⁻¹ y⁻¹ in NPK and control treatments, respectively. The respiratory loss of C (RLC) increased linearly with increasing input of C in soil and it ranged from 3.3 to 4.1 t ha⁻¹ y⁻¹ in different treatments with maximum in FYM and minimum in control treatment. The sugarcane biomass added in the soil humified at a rate constant of 0.38 in sub-tropical conditions and an addition of 3.9 t C ha⁻¹ y⁻¹ is required to maintain SOC in equilibrium. After 5 years of sugarcane cropping (one plant + four ratoons) an increase of 2.3–17.1 t ha⁻¹ in SOC over initial content was recorded with different treatments. Results in coming years from this long-term experiment shall add to the present calculated relationships between carbon addition and storage in sugarcane multi-ratooning crop production system under sub-tropical condition of India.     

Analysis of Genetic Diversity Among Saccharum spontaneum L. From Four Geographical Regions of India, Using Molecular Markers

Saccharum spontaneum L. a wild relative of sugarcane is the most variable and diverse among the Saccharum species. This species had been successfully exploited in sugarcane improvement programmes since 1915 and most of the present day commercial varieties are derivatives of interspecific hybrids involving S. spontaneum. The S. spontaneum germplasm available today in the World collections is diverse and represent different geographical groups. In the present investigation, an attempt was made to characterize 40 S. spontaneum clones collected from 4 different geographical areas in India using 20 random, 2 ISSR and 2 telomere primers. Of the 491 bands generated by these primers 83.9% were polymorphic. The genetic diversity estimated based on these markers was found to be moderate (48.9%). The pair-wise genetic distance between the accessions ranged from 29.8 to 60.0. The accessions from Arunachal Pradesh were found to be the most diverse, while Tamil Nadu accessions showed relatively less diversity. Diversity between Tamil Nadu and Kerala collections was found to be low, while the diversity between the Orissa group and the rest was found to be high. The collections from Mayurbanj and Cuttack regions of Orissa were found to be distinct. Arunachal Pradesh accessions, being more diverse, are a potential source for exploitation in sugarcane breeding programmes.     

Tolerance of potentially diazotrophic bacteria to adverse environmental conditions and plant growth-promotion in sugarcane

Sugarcane is one of the crops responsible for the high consumption of fertilizers in Brazil. To minimize this demand a sustainable alternative is to increase the studies to evaluate the beneficial effects of the relationship between plants/microorganisms, mainly plant growth-promoting bacteria. The objectives of this study were: a) to evaluate potentially diazotrophic bacteria isolates from sugarcane in adverse environmental conditions; b) inoculate these bacteria in sugarcane to evaluate their ability in plant growth-promotion. The study was carried in the Northeast of Brazil. Bacterial genera Burkholderia sp., Pantoea sp., Stenotrophomonas sp. and Enterobacter sp. were evaluated in different culture medium and later the bacterial isolates were inoculated in sugarcane evaluating the plant growth-promotion. Stenotrophomonas sp. and Pantoea sp. were tolerant to salinity and to different sources of carbon in acid medium and too tolerated high concentrations of pesticides and produced quorum sensing molecules (QS), but did not increase the dry matter production of sugarcane. Burkholderia sp. and Enterobacter sp. were more sensitive to salinity and pest control, but were more effective in plant growth-promotion. The tolerance of the bacteria to the adverse environmental conditions interfered negatively in the ability to plant growth-promotion.     

Effect of Nitrogen and Potassium Stress and Cultivar Differences on Potassium Ions and Nitrate Uptake in Sugarcane

ABSTRACT

This study was conducted to evaluate the effect of nitrogen (N) and potassium (K) stress on nitrate (NO₃ ^?) and potassium ion (K⁺) uptake of two sugarcane (Saccharum officinarum L.) cultivars known to differ with regard to their resistance to drought and salinity stress. The plants were hydroponically grown in a greenhouse and subjected to varying levels of N and K. Nitrogen and K stress increased root affinity for NO₃ ^? and K⁺ absorption by increasing apparent maximum uptake rate (V_max) and decreasing apparent affinity (K_m) for NO₃ ^? and K⁺ uptake in both cultivars. In addition, dry-matter allocation to roots increased with decreasing N and K supply. The results suggest that the acclimation to long-term N starvation in sugarcane involves regulation of both nitrate-specific assimilatory steps and growth responses. The cultivar ‘H69-8235,’ which was drought and salinity resistant, showed greater adaptability to a low- nutrient environment due to its higher root allocation and affinity for NO₃ ^? and K⁺ under N and K stress, suggesting that the resistance of sugarcane to multiple stresses may involve a general stress-response system.     

Growth and Nutrient Use in Four Grasses Under Drought Stress as Mediated by Silicon Fertilizers

Field water stress is a common problem in crop production, especially in arid and semi-arid zones and it is widely hypothesized that silicon (Si) could reduce water stress in plants. We set up a greenhouse study to evaluate some silicon sources—potassium silicate (K₂SiO₃), calcium silicate (CaSiO₃) and silica gel for growth and nutrient uptake by four grass species under adequate and deficit irrigation. The four species studied were Rhodes grass (Chloris gayana), Timothy grass (Phleum pratense), Sudan grass (Sorghum sudanense) and Tall fescue (Festuca arundinacea). For all species, the biomass yield response to applied silicon under deficit irrigation was significantly better than under adequate irrigation. The yield response of Rhodes grass across silicon sources was 205% under deficit irrigation compared with only 59% under adequate irrigation; for Sudan grass it was 49% compared with 26% and for Timothy, it was 48% compared with a mere 1%. The higher responses under deficit irrigation suggest that the plants relied more on silicon to endure drought stress. Biomass yield of individual plants also differed according to soil water levels with Timothy grass being the most sensitive to water stress as it exhibited the highest yield response (209%) to adequate irrigation. This was followed by tall fescue (122%) and Rhodes grass (97%). Sudan grass was the least affected by deficit irrigation, possibly on account of improved root mass and its natural drought tolerance. Strong associations were noted between the uptake of silicon and those of nitrogen (N) and phosphorus (P) irrespective of soil water condition, but the uptake of potassium (K) was more strongly correlated with that of Si under deficit than adequate irrigation. Improvements in plant growth following Si application could therefore be linked to enhanced uptake of major essential nutrients.     

Growth Response of Various Perennial Grasses to Increasing Salinity

ABSTRACT

Although the effect of salinity on plant growth has been the focus of a substantive research effort, much of this research has failed adequately to separate the various growth-limiting aspects of salinity; thus, the results are confounded by multiple factors. Eight perennial grass species were grown in a sand-culture system dominated by sodium chloride (NaCl) [electrical conductivities (ECs) between 1.4 and 38 dS m^?1], with sufficient calcium (Ca) added to each treatment to ensure that Na-induced Ca deficiency did not reduce growth. Of the eight perennial grass species examined, Chloris gayana cv. ‘Pioneer’ (Rhodes grass) was the most salt-tolerant species, while Chrysopogon zizanioides cv. ‘Monto’ (vetiver) was of only moderate tolerance. However, observed salinity tolerances tended to be lower than those expected from published values based on the threshold-salinity (bent-stick) model. This discrepancy may be due in part to differences in the evapotranspirational demand between studies; i.e., an increase in demand accelerates the accumulation of sodium (Na) in the shoots and hence decreases apparent salinity tolerance. It was also observed that the use of a non-saline growth period (to allow seed germination and establishment) results in the overestimation of vegetative salinity tolerance if not taken into consideration. This situation is particularly true for species of low salt tolerance, due to their comparatively rapid growth in the non-saline medium compared with growth at full salinity.     

Intra‐specific variation for salt tolerance in a potential oil‐seed crop,brown mustard (Brassica juncea (l.) Czern. and Coss.)

Thirty eight accessions of brown mustard (Brassica juncea (L.) Czern. and Coss.) were screened after two weeks growth in solution culture containing 120 mol m‐³ NaCl. Considerable variation for salt tolerance was observed in this set of germplasm, since some accessions showed relatively vigorous growth in saline medium.

In order to determine the consistency of degree of salt tolerance at different growth stages of crop life cycle two salt tolerant accessions, P‐15 and KS‐51 and two salt sensitive 85362 and 85605 were tested at the adult stage in 0(control), 100 and 200 mol m^‐3 NaCl. Both the tolerant accessions produced significantly greater fresh and dry biomass and had considerably higher seed yield than those of the salt sensitive accessions. Analysis of different ions in the leaves showed that salt tolerant accessions contained greater amounts of Na⁺, K⁺ and Ca²⁺ than the salt sensitive accessions, although they did not differ significantly for leaf Cl^‐. Only one salt tolerant accession P‐15 had greater leaf K/Na ratio and K⁺ versus Na⁺ selectivity compared with the tolerant KS‐51 and the two salt sensitive accessions.

From this study it was established that there is a considerable variation for salt tolerance in B.juncea which can be exploited by selection and breeding for improvement of its salt tolerance. Since the degree of salt tolerance in B.juncea does not change at different growth stages of the crop life cycle, selection for salt tolerance at the initial growth stages could provide individuals that would be tolerant at all other growth stages. Accumulation of Na⁺, K⁺ and Ca²⁺ in the leaves are important components of salt tolerance in B.juncea.     

Production potential of Stevia rebaudiana (Bert.) Bertoni. under intercropping systems

Abstract

Stevia (Stevia rebaudiana[Bert.] Bertoni.) is a crop of recent domestication in many countries. The cultivation of this plant in hilly and frost-prone areas provides an opportunity for intercropping of various food crops since the crop undergoes winter dormancy in India. This was studied through intercropping (additive series) at two spacings of the main crop, namely, 45×45 cm and 60×45 cm. Wheat, barley, lentil and gobhi sarson were intercropped. Intercropping reduced the production of S. rebaudiana up to 50% when compared to sole cropping. However, a row spacing of 60×45 cm resulted in less competition than the former, although, single cropping of S. rebaudiana produced the maximum stevioside. Intercropping with wheat increased the stevioside content when compared to other intercrops. The introduction of wheat resulted in higher monetary benefits at 60×45 cm spacing. Results indicated that reduction in S. rebaudiana biomass was mainly due to overlapping of the emergence period of the main crop with rapid growth and development of the intercrops. In conclusion, to lower competitive effects, the intercrop needs to be early maturity. Identifying suitable varieties for intercropping should be the priority research area to increase the productivity of the system.     

Identification of nutritional and environmental factors affecting sugarcane production in barbados

Abstract

Sugarcane production in Barbados has declined since the 1950s. Plant nutrition and fertilization deficiencies are generally believed to negatively influence yields in Barbados. The objective of this study was to identify nutritional and environmental factors related to sugarcane yields. Leaf analyses, respective crop yields, and other data were collected from the Barbados Sugar Industry Ltd. during the period 1985–1990. The database was constructed from 2,853 site observations, consisting of crop cane yield (Mt/ha), soil grouping, ecological grouping, growing elevation, and leaf tissue analysis [nitrogen (N), phosphorus (P), potassium (K)]. Simple mean separation and tree‐based regression were used to identify nutritional and environmental factors associated with sugarcane yields. Twenty‐three environments were delineated by tree‐based regression, in which plant nutrient deficiencies (i.e., yield limiting) were identified. One environment described N‐deficient conditions, four environments described P‐deficient conditions, and five environments described K‐deficient conditions. Different critical leaf nutrient concentrations were related to yields. A single nutrient norm under different environments may be misleading. If current fertilizer recommendations are adhered to by growers in Barbados, attention to additional fertilization should be given only under these environments.     

Effect of zeolite and phosphogypsum on yield,plant uptake,and content of strontium in soil

Abstract

Natural zeolite (clinoptilolite containing tuff) can be used as an adsorbent of strontium (Sr) from phosphogypsum when applied as a solonetzic soil amendment. This study investigated the influence of the zeolite on biological yield, content of water‐soluble Sr in soil, its availability, and plant uptake. A field experiment was conducted from 1993 to 1995 in the Volgogradskaya region of Russia. Two methods of phosphogypsum and zeolite application were used: “separate” and “as a mixture” (10 tons ha^‐1 of phosphogypsum and 0.5 ton ha^‐1 of zeolite in both cases). After the application of the amendments, barley (Hordeum vulgare) and grass sorghum (Sorghum sudanensis) were grown on the ameliorated sites in 1994 and 1995, respectively. Our results suggest that zeolite, being applied with phosphogypsum as a mixture, decreased by 15 to 75% the content of water‐soluble Sr in the soil, minimizing the risk of soil pollution. The uptake of Sr by plants depended on the biological character of the crop grown. Barley was found to be a “strong‐anticoncentrative” type of plant. However, grass sorghum was found to be more sensitive to the rise of Sr content in the soil. The highest biomass production of barley and grass sorghum was obtained with the application of zeolite and zeolite plus phosphogypsum. Plants grown on a single phosphogypsum‐treated sites had a declining tendency in biological yield. Our results suggest a positive influence of zeolite applied with phosphogypsum for the amelioration of solonetzic soils on the growth and uptake of Sr by plants.     

接种固氮菌Klebsiella sp.120对甘蔗光合特性和主要矿质营养元素含量的影响

【目的】甘蔗是最重要的糖料和能源作物,生物量大,产量高,但大量氮肥的使用不仅增加了甘蔗的种植成本,而且对农田环境造成了污染。发挥与甘蔗联合固氮的生物固氮菌的作用,是降低甘蔗氮肥施用量的方法之一。Klebsiella sp.120是从广西种植的甘蔗体内分离到的具有固氮能力的菌株。为了探讨该菌对甘蔗的促生效应及其在甘蔗上的应用潜能,本文研究了接种该固氮菌对甘蔗光合特性及矿质元素含量的影响。【方法】采用桶栽方法,在甘蔗的分蘖期用接种菌株淋浇4个不同甘蔗品种的根际,在处理后的30 d和60 d取样分析该菌对甘蔗的光合生理和矿质营养元素含量的影响。【结果】接种菌株对4个甘蔗品种的叶绿素含量和净光合速率有一定的促进作用,但不同品种之间存在差异。处理30 d后,淋浇固氮菌处理的甘蔗品种ROC22的叶绿素含量明显提高,比对照增加23%。另外3个甘蔗品种(B8、GT21和GT28)处理组的叶绿素含量均有一定的提高,但与对照相比差异不显著。处理30 d后,只有ROC22和B8品种的净光合速率高于对照,且ROC22品种处理与对照间的差异达到了显著水平。处理60 d后,4个甘蔗品种的净光合速率均高于处理30 d,而且各品种接种处理均高于对照,其中以对ROC22和GT21的促进效果最为明显,达到了显著水平。接种处理对不同甘蔗品种的营养元素含量影响不同,接种处理对4个甘蔗品种叶片中的氮元素含量有促进作用,其中对ROC22的促进效果最为明显,接种处理比对照增加59.8%。接种固氮菌对甘蔗叶片磷和钾元素含量的影响不明显。接种固氮菌对4个甘蔗品种叶片的铁、锰元素含量的影响不明显;ROC22叶片中的锌含量及ROC22和B8叶片中的铜含量接种处理与对照相比显著提高。【结论】接种Klebsiella sp.120固氮菌对甘蔗光合特性及矿质元素含量的影响与甘蔗品种有关,其中对ROC22品种的促生效果最为明显。研究结果可为固氮菌株Klebsiella sp.120在甘蔗上的进一步应用提供参考依据。     

Competitive ability of some cover crop species against Asystasia gangetica and Pennisetum polystachion

Abstract

Asystasia gangetica and Pennisetum polystachion are the most troublesome weeds in oil palm plantations in Malaysia and establishment of cover crops under oil palms is an integral part of sustainable weed management in plantations. Replacement-series experiments were conducted to evaluate the mode and strength of competitiveness of four legume cover crop species, Calopogonium caeruleum, Centrosema pubescens, Mucuna bracteata and Pueraria javanica, and one soft grass species, Axonopus compressus, against Asystasia gangetica and Pennisetum polystachion. Relative yield, relative yield total and relative crowding coefficient were calculated with reference to shoot biomass. Asystasia gangetica was a consistently weaker competitor than Pennisetum polystachion. The legume cover crop species had higher relative yield when grown in mixtures, whereas the yield of Asystasia gangetica was lower in mixtures with legumes than in monoculture. The higher competitiveness of legumes was due to greater canopy height and leaf area index. Centrosema pubescens was a slightly weaker competitor than the other legumes. Although leaf area per plant of Centrosema pubescens did not differ from that of other three legumes, canopy height and blocking photosynthetically active radiation to the soil surface were lower. When grown with a cover crop for 12 weeks, dry weight per plant, leaf area and shoot number of Pennisetum polystachion increased as its proportion decreased in mixtures. Relative yield data indicated that Pennisetum polystachion is a strong competitor. Axonopus compressus was less susceptible to Pennisetum polystachion interference than the legumes. All cover crop species studied proved highly competitive against Asystasia gangetica, but none could compete against Pennisetum polystachion. The study confirms the feasibility of using a cover crop for management of Asystasia gangetica.