Green Leaf Yield Research Articles

Comparing Application Methods for Boron Fertilizer on the Yield and Quality of Tobacco (Nicotiana tabacum L.)

The present study is based on the hypothesis that different methods of supplying boron (B) may have different effects on the yield and quality performance of tobacco crop. A field experiment was conducted to study the effect of different methods of B fertilization on the yield, quality, and leaf composition of flue-cured Virginia tobacco (cv. K-399) in 2007 at the Pakistan Tobacco Research Station, Mansehra. Three different methods (i.e., foliar spray, soil application, and root dipping at the rates of 0.25 kg ha–1, 1 kg ha–1, and 0.5 mg B L–1, respectively) in the form of boric acid along with a control (where no B was applied) were used in a randomized complete block design and replicated four times. Results revealed that different methods of B application significantly affected tobacco yield, quality, and nutrient uptake compared to the control. Maximum leaf area of 707 cm2, green leaf yield of 18553 kg ha–1, cured leaf yield of 2314 kg ha–1, grade index of 79%, nicotine content of 2.54%, and sugar content of 18.35% were noted in the treatment plot where B was applied as a foliar spray; however, in a few cases, there was no significant difference found among different methods of B application. Chloride and potassium contents were not significantly affected by any method of B fertilization. The B fertilization increased the concentration of this element in tobacco leaf, and a maximum concentration of B 48.55 mg kg–1 was noted in the foliar spray treatment. Moreover, fertilizer-use efficiency for different methods of B application revealed that foliar spray is more efficient as compared to soil application and root-dipping methods. Nutrient ratios to B such as potassium (K) / B and chloride (Cl) / B considerably decreased in tobacco leaf with increases in the concentration of B in leaves. These ratios provided some indication of the interrelationship of B with these nutrients in tobacco plants. Results also revealed that K/B and Cl/B ratios closely correlated with the grade index of tobacco leaf, and good grades of tobacco were found to be at a K/B ratio of 682 and a Cl/B ratio of 148 under the experimental conditions. The overall results indicated that the B foliar spray at the rate of 0.25 kg ha–1 significantly increased the yield, quality, and the nutrient uptake by the tobacco crop under the prevailing conditions and was more effective than other methods of B application.

Select criteria for yield of leafy amaranthus

Populations of amaranthus ( Amaranthus sp.) obtained from a physical-genetic admixture were studied to identify the best performing cultivars and determine the most important yield components. Most of the characters showed significant differences. Entries 15 and 29 performed best with entry 29 having the highest total green leaf yield. Significant correlations (P<0.01) were found between days to germination, to first harvest, days to second and third harvest, number of harvests, second and third harvest yield, with total yield. Path analysis revealed that second harvest yield makes the largest direct effect and had the highest significant (P<0.01) correlation with total yield. Number of harvests made the largest indirect effect on yield. It is clear that improvement of yield of leafy amaranthus can be achieved through increasing the frequency of harvests and yield in each harvest. Principle component analysis came to a similar conclusion.

بررسی روابط میان عملکرد برگ توتون و اجزای آن از طریق تجزیه علیت تحت شرایط نرمال رطوبتی و تنش خشکی

In order to study the relationship between dry leaf yield and some important characteristics of tobacco under drought stress and optimal conditions, 15 hybrid of tobacco, including 10 Iranian hybrids and 5 introduced hybrids from other countries were evaluated in two separate experiments (drought stress and normal) in a randomized complete block design with three replications, at the Research Center of Rasht, Iran, during 2008-2009. Results showed that under normal condition, there was positive and significant correlation between dry leaf yield and days to start flowering, flowering period, stem diameter and leaf area index, but dry leaf yield had negative and significant correlation with stem height. Under drought conditions, there was positive and significant correlation between green leaf yield and days to start flowering, leaf width and leaf area index, while there was no significant correlation between dry leaf yield and other traits. Path analysis of the correlation between dry leaf yield (as dependent variable) and other traits (as independent variables) showed that under non-stress conditions, days to start flowering, leaf length and stem diameter had direct effects on dry leaf yield, while under drought conditions, number of leaf, leaf width and days to start flowering had direct and positive effects. On drought stress conditions, the correlation between days to start flowering and green leaf yield was resulted from indirect effect of number of leaves per plant. To select for tobacco high quality leaves, we can select the best plants indirectly by using of days to start flowering, stem diameter and leaf length under normal water conditions and the number of leaves and leaf width under drought stress conditions.

The effect of a mixture of seed-borne Microdochium nivale var. majus and Microdochium nivale var. nivale infection on Fusarium seedling blight severity and subsequent stem colonisation and growth of winter wheat in pot experiments

Greenhouse experiments were conducted in order to determine the impact of seed-borne Microdochium nivale var. nivale and var. majus inoculum, and seed treatment with a carboxin+thiram mixture, on the development of seedling blight, and on subsequent stem colonisation and growth of winter wheat (cv. Cadenza). Experiments were conducted at temperatures favourable (3°C) and unfavourable (22°C) to M. nivale. Seed-borne inoculum resulted in seedling blight symptom development when plants were grown at 3°C, but not when plants were grown at 22°C. For seedlings grown at 3°C, plants arising from heavily blighted seedlings developed more severe symptoms of stem colonisation, when compared with those arising from seedlings from carboxin+thiram treated seeds. In addition, the vigour of such plants (assessed by determining the number of tillers and ears per plant, stem length, green leaf area, dry weight and yield) was also significantly lower than for plants arising from carboxin+thiram treated seeds. Microdochium nivale var. majus and var. nivale appeared to have little effect on plant vigour from seedlings grown at 22°C. This is the first recorded incidence of seedling blight affecting subsequent plant growth. Microdochium nivale var. majus and var. nivale stem colonisation increased from growth stage (GS) 40–49 to harvest in plants raised from seedlings grown at both temperatures. Microdochium nivale var. majus and var. nivale were isolated from the second node at GS 40–49 and the third node at harvest of plants from seedlings grown at 3°C. For plants from seedlings raised at 22°C, M. nivale var. majus and var. nivale were isolated from the first node at GS 40–49 and the second node at harvest. Carboxin+thiram seed treatment decreased the extent and severity of stem colonisation on plants from seedlings grown at 22°C.

Analysis of an introgressed Nicotiana tomentosa genomic region affecting leaf number and correlated traits in Nicotiana tabacum

Germplasm from closely related diploid relatives of tobacco (Nicotiana tabacum L.) could be of value for continued genetic modification of this species and for mapping quantitative trait loci (QTLs). We examined near isogenic tobacco lines and hybrids differing for an introgressed genomic region from N. tomentosa Ruiz and Pavon designated as Many Leaves that exhibits a large influence on leaf number and correlated traits. Within a 'Red Russian' genetic background, the region acted in an additive to partially dominant fashion to delay flowering time, and increase leaf number, plant height, and green leaf yield. Evidence of epistasis was observed as the region affected these traits to varying degrees in diverse near isogenic hybrids. Fifteen amplified fragment length polymorphism (AFLP) markers of N. tomentosa origin were mapped within a single linkage group of 34.5 cM using a population of 207 BC(1)F(1) individuals segregating for Many Leaves. Composite interval mapping produced 2-LOD confidence intervals for likely QTL positions influencing leaf number (3.1 cM region), plant height (2.9 cM region), and days to flowering (3.3 cM region). These intervals were overlapping. Results demonstrate that genomic regions with large genetic effects can be transferred to tobacco from closely related diploid relatives, and that sufficient recombination within these regions may permit mapping of genes controlling quantitative traits. Materials and results described here may be useful in future research to gain insight on the genetic control of the transition from vegetative to reproductive development in Nicotiana.

Evaluation of fungicides and biocontrol agents against Phomopsis canker of tea under field conditions

An experiment was conducted to study the efficacy of contact and systemic fungicides and biocontrol agents in controlling Phomopsis canker disease of tea under field conditions. Among the various treatments, soil application and wound dressing of biocontrol agents was found to be superior to fungicides in controlling Phomopsis canker. Dressing wounds with contact fungicides such as copper oxychloride and mancozeb was found ineffective whereas drenching soil with systemic fungicides such as carbendazim and contaf was moderately effective. Various treatments healed wounds to varying degrees and improved plant health. The bud break, tipping weight and green leaf yield were also increased to some extent in plants after treatments. Among the biocontrol agents tested, Gliocladium virens was better than Trichoderma harzianum in terms of curing cankers and increasing yield potential. The initial carbohydrate level of 9.38% increased with various treatments and was increased to 15.18% in cut-across pruned plants treated by soil application and wound dressing using G. virens. Similarly, the initial carbohydrate level of 9.15% increased to 11.89% when rejuvenated plants (pruned to healthy tissue) were treated with G. virens. In the case of the untreated control, the canker size increased from 6.37 by 2.24 cm to 8.57 by 3.17 cm and the plants appeared unhealthy with yellowing of the leaves and stunted growth associated with heavy flowering.

Effects of a strobilurin-based spray programme on disease control, green leaf area, yield and development of fungicide-resistance in Mycosphaerella graminicola in Northern Ireland

The effects of a range of strobilurin fungicides in programmes with the demethylation-inhibiting (DMI), epoxiconazole, or with chlorothalonil, were assessed in field experiments in Northern Ireland in 2004 and 2005 using the winter wheat cultivars Robigus and Savannah, partially resistant and moderately susceptible, respectively, to septoria tritici blotch. The development of strobilurin resistance was quantified using substitution of glycine by alanine in the target cytochrome b as a marker (G143A). Addition of strobilurins to epoxiconazole did not significantly reduce disease, increase green leaf area (GLA) or increase yield compared with epoxiconazole alone. However, azoxystrobin alone, despite failing to control disease or increase GLA, did increase yield compared with the untreated control. A mixture of azoxystrobin and chlorothalonil gave a significantly higher yield than either azoxystrobin or chlorothalonil alone. Higher frequencies of the strobilurin resistant allele (A143) were always selected for by treatments that included a strobilurin compared with those without. Frequencies of resistance were higher at the end of 2004 than at the start and there was a further increase in 2005. Field surveys of commercial winter wheat crops in 2004 and 2005 confirmed this trend of increasing strobilurin resistance in Mycosphaerella graminicola.

Morphological Characteristics of Perennial Ryegrass Leaves that Influence Short‐Term Intake in Dairy Cows

In sustainable agriculture, adaptation of swards to grazing is a major issue for breeding forage grass cultivars. Understanding the relationships between sward traits and animal production under grazing could help to identify criteria for selection. Intake is the major limiting factor for animal production under grazing. In this paper, short‐term intake rate by grazing dairy cows (Bos taurus) is compared between eight diploid perennial ryegrass (Lolium perenne L.) populations. Four replicates per population were measured over four periods (April and May 2001, and April and October 2002) in two experiments per period, that is, intermediate‐ and late‐maturity groups. For each period, sward structure was characterized by tiller density, leaf blade and sheath lengths, and green leaf and total dry matter (DM) yield, while nutritive value was characterized by in vitro dry matter digestibility (IVDMD), percent of DM, N, water‐soluble carbohydrate (WSC), and neutral‐detergent fiber (NDF) contents. For the late‐maturity populations, the population with the shortest leaves had a lower fresh matter intake rate (10.5 kg h−1) than the three others (12, 12, and 11.6 kg h−1, respectively). For the intermediate‐maturity populations, differences in intake rates among populations were significant (P = 0.06) for all periods and were highly significant (P &lt; 0.0004) in April 2002. In this period, 49% of the variation in fresh matter intake rate could be explained by blade length. In conclusion, differences in short‐term intake rate between populations of diploid perennial ryegrass are highlighted. In both maturity groups, blade length appears to be an important factor explaining these differences.

Nitrate Reductase Activity in Tea as Influenced by Various Levels of Nitrogen and Potassium Fertilizers

Leaf and root samples were collected from experimental blocks treated with different levels of nitrogen and potassium (NK) and analyzed for nitrate reductase (NR) activity. It was inferred that in a tea shoot consisting of three leaves and a bud, the NR activity was higher in first leaf followed by third leaf and feeder roots. Increase in NR activity was noted due to the increase in N or K fertilizer doses. There existed a significant correlation between green leaf yield and NR activity recorded at first and second harvesting rounds after manuring. Activity observed at the Anamallais was slightly higher than that seen in the Nilgiris. The activity was maximum on the seventh day after fertilizer application and it was considerably high up to 28th day, which revealed that the minimum interval between two successive NK fertilizer applications should be one month. The N:K2O ratio 1:1 appears to be optimum when 300/450 kg of N as urea (or) K2O as muriate of potash ha−1 yr−1 was used.

A temporal limit to the association between flag leaf life extension by fungicides and wheat yields

Three field experiments, each repeated over two or three seasons, on winter wheat investigated a possible limit to the association between grain yield and flag leaf life, as extended by fungicide application. The experiments involved up to six cultivars and different application rates, timings and frequencies of the strobilurin azoxystrobin and the triazole epoxiconazole. In the 2000/01 and 2001/02 seasons, the relationships between the thermal time to 37% green flag leaf area ( m) and yield deviated from linearity. ‘Broken stick’ models were fitted to cultivar × experiment combinations within each season and the limit to the benefit to yield associated with extending flag leaf life was 700 °C days (S.E. = 20.7) and 725 °C days (S.E. = 9.33) after anthesis in 2000/01 and 2001/02, respectively. In 2002/03, the relationship between yield and m did not deviate significantly ( P > 0.05) from linearity, but in this latter year the fungicide application failed to increase m past 700 °C days.

Disease management of spring barley with reduced doses of fungicides in Northern Ireland

Trials over 8 years in Northern Ireland with a range of fungicides, applied at a range of doses, to spring barley showed a reduction in disease and increase in green leaf area and yield, particularly from 1993 to 97, when mildew ( Blumeria graminis f.sp. tritici) was the main disease. Fungicides in those years had considerable effect even at low doses. In the latter years of the project, there was relatively little mildew or leaf blotch ( Rhynchosporium secalis) and the effect of fungicides was less. Results generally indicate that the potential of disease resistance of cultivars should be fully exploited and prophylactic spraying at present is unlikely to be profitable.

Productivity, quality and economics of irrigated FCV tobacco (Nicotiana tabacum) in relation to spacing, dose and time of nitrogen application

A field experiment was conducted during post-rainy season of 2000-01, 2001 -02 and 2002-03 at Jeelugumilli to find out optimum spacing, dose and time of N application to flue-cured virginia (FCV) tobacco (Nicotiana tabacum L) in irrigated Alfisols (Northern Light Soils) of Andhra Pradesh. Green leaf yield, cured leaf yield and grade index were significantly higher at a spacing of 100 x 70 cm compared with 100 x 60 cm. Significant increase in green- leaf yield and cured leaf yield was noticed with increase in N level from 90 to 130 kg N/ha. Application of 130 and 11 0 kg N/ha, being comparable, recorded significantly higher grade index than that of 90 kg N/ha. Application of N in three splits offered significantly higher green leaf yield, cured leaf yield and grade index compared with that of N in two splits. Wider spacing gave higher total N and nicotine levels and lower reducing sugars, equilibrium moisture content (EMC) and filling value of leaf than closer spacing. There was a gradual decrease of sugars and EMC and increase of nicotine, total N and filling value with increased levels of N. Application of nitrogen in three splits gave higher total N, nicotine and filling value and lower reducing sugars and EMC of cured leaf than that of N in two splits. Maximum net returns and benefit : cost ratio accrued when planted at 100 x 70 cm spacing along with 11 0 kg N/ha applied in three splits. A spacing of 100 cm x 70 cm along with 11 0 kg N//ha applied in three splits, was found optimum for cv. 'Kanchan' for obtaining higher yield and better grade index with acceptable chemical and physical quality parameters.

Effect of application of biofertilizers to soybean (Glycine max) and nitrogen to tobacco (Nicotiuna tabacum) in soybean - tobacco cropping system

A field experiment was conducted during 2001-02 and 2002-03 at Jeelugumilli to find out the direct and residual effects of Bradyrhizobium japonicum and Pseudomonas striata inoculation on rainy season (kharif) soybean [Gly- cine max (L.) Merr.] cv 'JS 335' and of directly applied N in winter (rabr) season FCV tobacco (Nicotiana tabacum L.) cv 'Kanchan' in irrigated Alfisols of Andhra Pradesh. Co-inoculation of soybean with Bradyrhizobium + Pseudomonas recorded significantly higher growth, yield attributes and grain yield than their individual inoculation and no inoculation. Green-manuring in situ with sunnhemp [Crotalaria juncea (L.) Rotar &amp; Joy] followed by tobacco recorded significantly higher tobacco green-leaf and cured-leaf yields, and grade index compared with other treat- ments. Combined inoculation of Bradyrhizobium and Pseudomonas to soybean increased the tobacco green leaf yield, cured leaf yield and grade index by 10.5, 7.7 and 13.2% respectively compared with no inoculation. Applica- tion of 130 kg Nlha recorded significantly higher green-leaf and cured-leaf yields, and grade index compared with that of 11 0 kg Nlha. Higher total N, nicotine, lower reducing sugars and sugar: nicotine ratio in X and L leaf posi- tions were observed in sunnhemp-tobacco system, followed by soybean (co-inoculation) - tobacco system. Higher total N, nicotine, lower reducing sugars and sugar : nicotine ratio were recorded with 130 kg Nlha than with 11 0 kg Nlha. Soybean (co-inoculation) - tobacco system gave additional net returns of Rs 1,7101ha over sunnhemp-tobacco system (Rs 40,670lha). Higher B : C ratio of 1.65 was obtained with sunnhemp - tobacco sys- tem. It was concluded that combined inoculation of Bradyrhizobium and Pseudomonas to soybean improved the growth and yield of soybean and increased the succeeding tobacco yields, and application of 130 kg Nlha would be needed for tobacco succeeding soybean.

The influence of kangaroos and forage on sheep productivity in the semi-arid woodlands.

Problems of pasture degradation and competition from kangaroos in the semi-arid woodlands were investigated in a grazing trial conducted in western New South Wales. The trial area of 200 ha was subdivided into 12 paddocks, varying in size from 7.5 to 30 ha and grazed with matched groups of six merino hoggetts, with and without a similar number of western grey kangaroos. Stocking rates were 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8 sheep per hectare and 0.2, 0.27, 0.33, 0.4, 0.47 and 0.53 sheep per hectare, with an equal number of western grey kangaroos. Wool growth and weight gain of the sheep, and the yield of forage species and components, were recorded quarterly over a three year period. Rainfall received over these years was close to the 30, 90 and 50 percentile levels respectively. The results were analysed by regression modelling. Both wool growth and sheep weight gain were reduced by increasing stocking rates of sheep or kangaroos, except when forage was abundant. The relative effect of kangaroo grazing was greatest in the year of lowest rainfall, with an equivalence of one sheep: 0.6 kangaroo of equal weight. Forage biomass declined as stocking rates increased with kangaroos having the equivalent effect of 0.75 sheep on a weight for weight basis. More than 80 per cent of the variation in clean fleece weight (CFW, kg/year) and annual sheep weight gain (WG, kg/year) was explained by the average yield of green herbage leaf (GL, kgtha) in the expressions and CFW = 1.30 + 0.72 In GL WG = 5.6 In GL These results show that sheep productivity can be increased by controlling kangaroo numbers in the drier years. They also indicate that productivity can be raised by increasing the abundance of palatable perennial species, which maintain green leaf during periods of moderate and low rainfall.

Endophytic Fungi in Propiconazole-Treated and Untreated Barley Leaves

The presence of endophytic fungi in the second leaf below the shoot apex from field-grown barley was investigated after surface sterilizing the leaves. Half of the eight experimental plots were sprayed with the systemic fungicide propiconazolc and changes in the fungal population recorded. Green leaf area and yield parameters were measured to draw conclusions about the significance of endophytic fungi on grain yield. Alternaria spp. (55% of all isolates) and Didymella phleina (20%) were isolated most frequently while Stemphylium botryosum, Epicoccum purpurascens and Cladosporium spp. were often abundant. In propiconazole-treated plots significantly fewer isolates of D. phleina, Alternaria and Cladosporium were obtained, the decline of green leaf area was retarded and grain yield was higher. There was no evidence that one of the frequently found saprobes had accelerated senescence. Therefore, the control of D. phleina or cytokinin-like properties of propiconazole equally may have contributed to a yield increase in sprayed plots. The persistence of endophytic fungi in barley leaves seemed to be low and most dependent on climatic conditions and the presence of external inoculum.

Endophytic Fungi in Propiconazole-Treated and Untreated Barley Leaves

The presence of endophytic fungi in the second leaf below the shoot apex from field-grown barley was investigated after surface sterilizing the leaves. Half of the eight experimental plots were sprayed with the systemic fungicide propiconazole and changes in the fungal population recorded. Green leaf area and yield parameters were measured to draw conclusions about the significance of endophytic fungi on grain yield. Alternaria spp. (55% of all isolates) and Didymella phleina (20%) were isolated most frequently while Stemphylium botryosum, Epicoccum purpurascens and Cladosporium spp. were often abundant. In propiconazole-treated plots significantly fewer isolates of D. phleina, Alternaria and Cladosporium were obtained, the decline of green leaf area was retarded and grain yield was higher. There was no evidence that one of the frequently found saprobes had accelerated senescence. Therefore, the control of D. phleina or cytokinin-like properties of propiconazole equally may have contributed to a yield increase in sprayed plots. The persistence of endophytic fungi in barley leaves seemed to be low and most dependent on climatic conditions and the presence of external inoculum.

The effect of powdery mildew (Erysiphe graminis f. sp. hordei) and leaf rust (Puccinia hordei) on spring barley in New Zealand. I. Epidemic development, green leaf area and yield

Powdery mildew and leaf rust caused large yield losses in spring barley grown near Christchurch, New‐Zealand, in two seasons. Disease present during early growth stages was as damaging to yield as disease late in the season. Moderate leaf rust severities after anthesis were most damaging when combined with earlier mildew epidemics. Later growth did not compensate for reduced yield potential induced by early infection. This was attributed, at least in part, to an effect on leaf size, and therefore on green leaf area, at later growth stages. There was a closer relationship, by regression analysis, of yield to green leaf area than to disease severity in three cultivars.The three cultivars. which differed in yield potential and disease resistance, were not equally sensitive to disease. It is proposed that high yielding cultivars may be the most sensitive to yield constraint by disease.

Persistence and productivity of ten perennial Urochloa genotypes with Stylosanthes species in far north Queensland

Ten perennial accessions of 4 Urochloa species and Brachiaria decumbens cv. Basilisk were sown with a mixture of Stylosanthes species at 6 sites in north Queensland's dry tropics to measure their persistence, productivity and compatibility with legumes. Out of a total of 8 sowings, as 2 sites were resown, grasses failed to establish at all but 3 sites, and at 1 of these, on a sandy soil, they failed to persist. At the remaining 2 sites (Southedge and Boomerang), 4 years after sowing, all sown species were present as dense, weed-free stands averaging 61 and 37% sown grass and 20 and 38% legume by weight. Legume made up a higher proportion of dry matter yield late in the wet season than at the beginning of the wet season. Yield of Basilisk was above average at 9 of the 12 harvests at these 2 sites, while U. mosambicensis CPI 46876 and U. oligotricha CPI 47122 were each always above average at 1 of the sites. Legume yield was not related to sown grass. Yield of green leaf by sown grasses in spring was related to crown density rather than to genotype.

Grazing studies on the Guadalcanal Plains, Solomon Islands. 2. Effects of pasture mixtures and stocking rate on animal production and pasture components

SummaryAnimal production was compared on three pastures, Brachiaria mutica (para), B. decumbens (signal) and Panicum maximum cv. Hamil (hamil) each sown with a common legume mixture of Centrosemapubescens (centro), Macroptilium atropurpureum cv. Siratro, and Stylosanthes guianensis cv. Endeavour (stylo), at four stocking rates, 1·8, 21·87, 31·86, and 41·85 animals/ha, over 4 years on the GuadalcanalPlains, Solomon Islands.Mean live-weight gain per head over the four stocking rates and 4 years on para pastures was 01·847, on signal pastures 01·838, and on hamil pastures 01·828 kg/head/day. Mean production per hectare at the optimum stocking rates were: para at 3.6 animals/ha, 607 kg; signal at 31·86 animals/ha, 442 kg; hamil at 21·87 animals/ha, 362 kg/ha/year.The high stocking rates of 31·86 and 41·85 animals/ha caused the hamil pastures to decline to the stage where they were destocked in the 4th year of grazing.Superior production on para pastures was not simply related to green dry matter (GDM) on offer. In the 1st year of grazing, GDM was highest in hamil pastures, but in the 2nd year highest in para, and in the 3rd year mean yields were similar in all pastures, but were very low at the 31·86 and 41·85 animals/ha stocking rate in the hamil pastures.Para pastures maintained highest legume contents. The quadratic relationship between live-weight gain/head and legume content was significant over all pastures and stocking rates. Live-weight gain (LWG) per head increased up to 15% legume content, after which there was little change. Yield of green leaf, percentage green leaf, and sward bulk density did not appear to be related to LWG/head. Para pastures had lower values for all these components than the other pastures.Chemical factors contributed to the higher animal production from para pastures. Para leaf maintained consistently higher in vitro dry-matter digestibility values. Na content of para averaged 01·812%, whereas other species were 01·801 to 01·802%, and below the critical level (01·805%) for animal intake. N and S in leaf material, and Cu in total tops were also consistently higher in para grass.Results of this grazing trial suggest that selection of grass species on the basis of quality including dry-matter digestibility and mineral content, on ability to persist with increasing stocking rate, on compatibility with legumes, and on growth habit are more important than selection for dry-matter yield.

Effect of some field variables on the dry-matter content of tea shoots

Beverage tea is produced from the immature shoots manually harvested from the perennial shrub Camellia sinensis (L.) O. Kuntze. Fresh green leaf is mechanically comminuted and converted to the black tea of commerce by a series of partially controlled biochemical oxidation reactions (Sanderson, 1972). The final, unrefined dried product represents some 20% of the initial fresh weight of crop, the actual dry-matter content of the harvested shoots determining the percentage made-tea return (Keegel, 1955). Dry-matter content, hence, influences yield in terms of black tea produced. Although theeffectsof environmental, agronomic and cultural factors on green leaf yield have been studied intensively, little work has been done on the influence of such factors on dry-matter content. The present study examines the effects of nitrogen application rates on dry-matter content in four genetically diverse clonal populations throughout the main production season and during the first period of the Central African off-season.