Direct and Residual Contributions of Symbiotic Nitrogen Fixation by Legumes to the Yield and Nitrogen Uptake of Maize (Zea mays L.) in the Nigerian Savannah

Field experiments were conducted to determine the direct and residual contributions of legumes to the yield and nitrogen (N) uptake of maize during the wet seasons of 1994 and 1995 at the University Farm, Abubakar Tafawa Balewa University, Bauchi, Nigeria, located in the Northern Guinea savannah of Nigeria. Nodulating soybean, lablab, green gram and black gram contributed to the yield and N uptake of maize either intercropped with the legumes or grown after legumes as a sole crop. Direct transfer of N from the nodulating soybean, lablab, green gram and black gram to the intercropped maize was 24.9–28.1, 23.8–29.2, 19.7–22.1 and 18.4–18.6 kg N ha^–1, respectively. However, the transfer of residual N from these legumes to the succeeding maize crop was 18.4–20.0, 19.5–29.9, 12.0–13.7 and 9.3–10.3 kg N ha^–1, respectively. Four years of continuous lablab cropping resulted in yields and N uptake of the succeeding maize crop grown without fertilizer N that were comparable to the yields and N uptake of the succeeding maize crop supplied with 40–45 kg N ha^–1 and grown after 4 years of continuous sorghum cropping. It may therefore be concluded that nodulating soybean, lablab, green gram and black gram may be either intercropped or grown in rotation with cereals in order to economize the use of fertilizer N for maize production in the Nigerian savannah.     

Biochar has little effect on soil dissolved organic carbon pool 5 years after biochar application under field condition

Biochar application can improve soil properties, such as increasing soil organic carbon content, soil pH and water content. These properties are important to soil dissolved organic carbon (DOC); however, the effects of biochar on DOC concentration and composition have received little research attention, especially several years after biochar application under field conditions. This study was conducted in a long‐term experimental field where the biochar was only applied once in 2009. The purpose of the study was to investigate the effect of different biochar application rates (0, 30, 60 and 90 t ha^?1) on the dynamics of soil water content, DOC concentration and DOC compositions (reducing sugar, soluble phenol and aromatics) over nine samplings during a 12‐month period in 2014. Our results showed that soil water content and DOC concentration varied from 7.1% to 14.5% and 59 to 230 mg C kg^?1 soil during the 12 months, respectively. However, the biochar application rates did not significantly (p > 0.05) affect soil water content, DOC concentration and DOC composition at the same sampling period. The DOC concentration across the biochar treatments was positively correlated to soil water content. Moreover, the DOC composition (reducing sugar, soluble phenol or aromatics) and their concentrations were positively correlated to the total DOC concentration. In addition, biochar did not affect soil bulk density, pH, saturated hydraulic conductivity and crop yields. The results indicated that some benefits of biochar to soil may not persist 5 years after the application of biochar under a field condition.     

Higher than optimum temperature under CO2 enrichment influences stomata anatomical characters in rose (Rosa hybrida)

There is little available information on the effects of temperature and CO₂ enrichment on stomata anatomical characteristics of plants. Effect of these two microclimates was studied on five rose (Rosa spp.) cultivars, viz. ‘First Red’ (used as check), ‘Arjun’, ‘Raktima’, ‘Raktagandha’ and ‘Pusa Pitamber’. Budded, single-stemmed rose cultivars having five lateral buds were grown in controlled environment growth cabinets under enriched CO₂ (1000 μmol mol⁻¹) and optimum (28/18 °C, T₀) or high (35/25 °C, T₁) temperature for 50 days. All observations were made on the abaxial leaf surface. Significant increases in stomatal density (68.7%), index (29.6%) and epidermal cell density (37.3%) were recorded in plants grown at high temperature over control with CO₂ enrichment. The cultivars responded differently in terms of length and width of guard cell and stoma (pore) under high temperature, however, the values averaged over treatments showed a significant reduction in these parameters. Further, number of stomata per leaf was higher (28.3%) in plants grown at high temperature, except First Red. A reduction in mean leaf area (26.7%) and dry mass (32.0%) was recorded at high rather than optimum temperature. The specific leaf area was maximum in Arjun (87%) while in First Red, a 14% reduction was noted at high temperature.     

Evaluation of purgative activity of roots of Rumex nepalensis

The methanol extract of Rumex nepalensis Spreng. roots at the oral dose of 100-400 mg/kg exhibited significant and dose-dependent purgative activity.     

Variation in Shoot Anatomy and Rooting Behaviour of Stem Cuttings in Relation to Age of Donor Plants in Teak (Tectona grandis Linn. f.)

Shoot anatomical features viz., number of vessel elements, width and length of vessel and fibre elements were studied in relation to juvenility/maturity of teak (Tectona grandis Linn. f.). The findings show significant differences in these features, which indicates that variation in shoot anatomy can be used as a reliable indicator of juvenility/maturity in teak. The effect of age of donor plants and application of auxins on adventitious root formation in single noded leafy stem cuttings of teak was also investigated. Aging of donor trees suppressed rooting and sprouting of cuttings, but increased callus formation at the base of cuttings. Per cent rooting and per cent sprouting in cuttings decreased as age of donor plants increased from 2-months to 15-years and up to 30-years. IBA treatment promoted per cent rooting as well as per cent sprouting, NAA promoted only rooting and it suppressed sprouting. The effect of auxin treatment on rooting and sprouting of teak stem cuttings varied with the age of donor plants. Auxin and its concentration, which suppressed rooting and sprouting in cuttings of younger donor plants, actually promoted rooting when cuttings were taken from more mature donor plants. It appears that the auxin requirement for causing and promoting rooting in teak cuttings increased with increasing age of donor plants. The higher auxin requirement for causing and promoting rooting in cuttings of older trees may be due to a decrease in the content on endogenous auxins or decreased sensitivity of aging tissues to rooting promoters and /or accumulation of inhibitory substances which inhibit rooting.     

Status of floor vegetation under some monoculture and mixculture plantations in North India

A study conducted to assess the floor vegetation shows the presence of 17 species underPopulus deltoides in comparison to 28, 29 and 35 underAlbizia lebbeck, Dalbergia sissoo and mix-culture plantations, respectively. Further, the biomass and density of floor vegetation is considerably reduced underP. deltoides compared to other plantations. In addition, the indices for species richness, evenness, dominance and diversity are also reduced underP. deltoides showing some inhibitory mechanism being operative under these plantations. Based on available literature, allelopathy is speculated to be responsible for this reduction.     

Comparison of Composition,Protein, Pasting,and Phenolic Compounds of Brown Rice and Germinated Brown Rice from Different Cultivars

Physical characteristics, amino acids composition, protein profiling, pasting characteristics, and phenolic compounds of brown rice (BR) and germinated brown rice (GBR) from different paddy cultivars (PB1, PS44, PB1509, PB1121, and PS5) were investigated. L* (lightness) decreased, but a* (redness and greenness) and b* (yellowness and blueness) increased with germination. Protein and ash content increased, whereas fat and amylose contents decreased with germination. GBR showed lower hardness and gumminess than BR. Foam stability and water absorption capacity from GBR flour were higher compared with BR flour. Accumulation of γ‐aminobutyric acid, histidine, arginine, proline, methionine, and acidic amino acids increased significantly with germination, and increase was related to change in accumulation of glutelin and prolamins. The accumulation of prolamins and glutelin acidic and basic subunits decreased with germination. GBR flour showed lower pasting viscosities compared with BR flour. Ferulic acid, p‐coumaric acid, and quercetin were present in both fractions of the bound form. GBR showed improved nutritional quality that varied in different cultivars. PB1121 was observed to be the best for producing GBR owing to greater changes brought in protein content, essential amino acids, catechin, chlorogenic acid, protocatechuic acid, vanillic acid, and foam stability.     

Intensive management of a bamboo forest significantly enhanced soil nutrient concentrations but decreased soil microbial biomass and enzyme activity: a long-term chronosequence study

Purpose

Intensive long-term management practices in forest ecosystems can markedly influence soils’ physicochemical and microbial properties. However, their effects on the magnitude of nutrient pools and activities of enzymes regarding nutrient cycling in subtropical forest soils remain unclear. This study aimed to examine effects of long-term intensive management (organic mulching and chemical fertilization) on concentrations of different C, N, and P fractions and activities of enzymes involved with nutrient cycling in a subtropical Lei bamboo (Phyllostachys violascens) forest soil.

Materials and methods

Soil samples were taken from a chronosequence of Lei bamboo forests with intensive management spanning 0, 5, 10, and 15 years. Concentrations of various forms of C, N, and P, as well as activities of β-glucosidase, cellobiohydrolase, urease, protease, and acid phosphatase were measured.

Results and discussion

The results revealed that the concentrations of different classes of C (water-soluble organic C, hot-water-soluble organic C, and readily oxidizable C), N (NH₄⁺-N, NO₃^?-N, and water-soluble organic N), and P [resin-inorganic P (P_i), NaHCO₃-P_i, NaHCO₃-organic P (P_o), NaOH-P_i, NaOH-P_o, HCl-P_i, and residual-P] were enhanced markedly with prolonged duration of intensive management. Furthermore, activities of β-glucosidase, cellobiohydrolase, urease, protease, and acid phosphatase were increased following a 5-year treatment, while they were markedly reduced from 5- to the 15-year treatments. The 15 years of intensive management significantly reduced microbial biomass C and N concentrations by 8.2% and 31.9%, respectively, compared to the control.

Conclusions

We concluded that long-term intensive management led to the accumulation of C, N, and P, while it negatively impacted microbial biomass and activities of enzymes involved in nutrient cycling in subtropical Lei bamboo forest soils. Consequently, a reduction in chemical fertilizers should be considered toward the long-term sustainable development of subtropical Lei bamboo forests.

     

Temporal variation of soil nutrients under the influence of different organic amendments

Maintenance of tropical soil quality for crop production without damaging the environment is a challenge and thus the development of an efficient nutrient-management technique is important. Soil amendment by organic manures has been widely accepted as an efficient nutrient-management technique in tropical agriculture. In this study, a long-term laboratory experiment was conducted to investigate the influence of organic manures of different sources (e.g. cattle manure, poultry manure, vermicompost and oil cakes) on changes in pH, electrical conductivity, organic C and nutrient content (mineral N, available phosphorous and potassium) in tropical alluvial soil. Applications of organic amendments in this study indicated considerable changes in the basic soil physico-chemical properties and different nutrient levels. Soil pH declined slightly, whereas organic C and all the other nutrients increased distinctly, due to the application of organic manures. Thus, the magnitude of changes in the soil properties was dependent on the nature of the organic manure.     

Response of Rainfed Sunflower (Helianthus annuus L.) to Nitrogen Rates and Plant Population in the Semi-arid Savanna Region of Nigeria

Field experiments were conducted during the wet seasons of 1991,1992 and 1993 at the Abubakar Tafawa Balewa University Farm, Bauchi (10 ° 22'N, 09 ° 47'E) to study the response of sunflower ( Helianthus annaus L.) to N rates and plant population under rainfed conditions. Four N rates (0, 50, 100 and 150 kg N ha ^-1) and four plant populations (40000,80000,120000 and 160000 plants ha^-1) were factorially combined in a randomized complete block design with three replications. Leaf area index, shoot dry weight and seed yield (kg ha^-1) increased significantly with increasing N rates from 0 to 100 kg N ha^-1. The growth and yield parameters per plant decreased significantly with increasing plant populations from 40000 to 160000 plants ha^-1, but the seed yield (kg ha^-1) obtained at 80000 plants ha^-1 was significantly higher than all the other plant populations. The interactions of N x plant population confounded the main effect of each factor on the growth and yield of sunflower. The seed yield (3425 kg ha^-1) obtained from the use of 100 kg N ha^-1 at 80000 plants ha^-1 was significantly higher than those obtained from all other combinations of N x population and out-yielded the main effects of 100 kg N ha^-1 and 80000 plants ha^-1 by 18 % and 25 %, respectively. The use of 100 kg N ha^-1 at 80000 plants ha^-1 is therefore recommended for maximum yield of sunflower in Bauchi.