Tonnes Ha-1 Research Articles

Effect of Mulching on Soil Temperature and Moisture Regime on Emergence, Growth and Yield of White Yam in a Tropical Wet-and-Dry Climate

An on-farm yam experiment was conducted to study the effect of mulching on soil temperature and moisture regime on white yam (Dioscorea rotundata) growth and yield in Abeokuta, South-western Nigeria. Three mulching options (grass mulched, polythene mulched and unmulched) was selected and related to crop growth and yield. Grass mulch sig- nificantly (P < 0.05) lowered maximum soil temperature by 1-2℃ at 15cm depth during the thermal critical period (Janu- ary - March). This led to higher rate of emergence which accounted for 28 and 46% to the polythene mulch and the un- mulched plots respectively. Furthermore, grass mulch had tuber yield of about 4-6 tonnes ha-1 season-1 greater than the polythene mulch and the unmulched plots. Irrespective of mulching materials, it was found that mulching significantly (P< 0.05) increased tuber yield by about 6-8 tonnes ha-1 season-1 than the unmulched. The effect of grass mulch over nylon mulch on yam performance in the study was also discussed.

COMPARATIVE STUDY OF THE QUALITY OF LABLAB (Lablab purpureus L. Sweet) SILAGE AND HAY MADE BY UNCONVENTIONAL METHODS

Lablab purpureus which may yield over 60 and 15 tonnes ha-1 of fresh and dry herbage respectively can be conserved as silage during the rainy season for feeding ruminants in the dry season. A two-year study evaluated the effect of four forage conservation methods (3-silage and 1-hay) on the proximate parameters of conserved lablab. Minimal spoilage losses due to termites was observed in silage produced on bare ground surface. The proximate parameters were more favourable in the case of lablab silage than hay with crude protein concentration (14.7%) being 80% higher in the silage than in hay (8.1%). Among the different silage production methods bag ensiling was superior because of the ease of handling and the higher crude protein concentration(23.4%) which is more than adequate for ruminant lactation (12%) and growth (11.3%). Protein concentrate supplementation may be unnecessary when bag ensiled lablab silage is used for dry season feeding of livestock. Cutting lablab at 12 weeks after sowing for silage production is advantageous and may reduce crude protein wastages by over 20% while ensuring up to 37% of the expected seed yield of lablab at maturity.

RESPONSE OF LETTUCE (Lactuca Sativa L.) TO DIFFERENT ORGANIC MANURES AT VOM, PLATEAU STATE, NIGERIA

A two-year study was conducted to test the effect of various organic fertilizers on the growth and yield of lettuce (Lactuca sativa L.). The treatments which were laid out in a randomized block design and replicated three times consisted of a zero manure control, cow dung, poultry and rabbit manures applied at 30 tonnes ha-1. Poultry manure consistently and significantly produced the tallest plants (by 24 % and 49 %) and more leaves (by 45 % and 101 %) at 2- and 10 weeks after transplanting respectively compared to the control. The study showed that lettuce leaves can be harvested as from 6 weeks of age (with about 16 leaves) and fed to rabbits. Lettuce grown with organic manure did not contain parasitic pathogens and can therefore not become a direct source of infection to animals fed on the produce. In the absence of poultry manure, rabbit manure is a satisfactory substitute for leaf lettuce production. Organic vegetable producers should be mindful of the possibility that pathogenic parasites in their growing media may contaminate the greengrocery

Growth, yield and NPK uptake by maize with complementary organic and inorganic fertilizers.

High and sustainable crop yields in the tropics have been reported to be only possible with judicious combination of mineral fertilizers and organic amendments. Fertilizing croppings to achieve this has usually been a difficult task to achieve. The growth and yield of maize cultivated with a complementary application of organic and inorganic fertilizers was assessed compared with sole organic and sole inorganic fertilizers between April and July 2003 and 2004 at Ibadan, Nigeria, in the degraded tropicalrain forest zone. There was a no-fertilizer treatment as the control. The organic fertilizer was an equal mixture of composted domestic waste and stale cow dung, applied at 10 tonnes ha-1. Urea and Single super phosphate were applied as the inorganic fertilizer to supply 70 kg N and 13 kg P2O5 ha-1 respectively. The mixture of organic and inorganic fertilizer treatment consisted of half the rates used for sole organic and sole inorganic fertilizer treatments: 5 tonnes organic mixture was applied, with 35 kg N and 6.5 kg P2O5. Maize plant height at 8 weeks after planting washighest with inorganic fertilizer application while the leaf area was highest with organic fertilizer application. Stover yield and cob yields were also highest with inorganic fertilizer. Complementary application of organic and inorganic fertilizers however had similar plant heights; stover yield as well as cob yields with inorganic fertilizer. Nitrogen appeared chelated with organic fertilizer application. Plant ear – leaf Nitrogen was highest (1.68%) with inorganic fertilizer while the control plots had a Nitrogen content of 1.12% which was higher than 0.84% and 0.98% N from sole organic and a complementary application of organic and inorganic fertilizers, respectively. Plant P content was increased by 136% and 15% with organic and inorganic fertilizers, respectively, but was reduced by 15% with complementaryapplication of organic and inorganic fertilizers. The K content was highest with inorganic fertilizer (1.91%). Complementary application of organic and inorganic fertilizers had a K content of 1.70% while the organic – fertilized leaves had 1.53%. Stover nutrient uptake was highest for N and K with inorganic fertilizer while the P was highest with organic fertilizer application. Cultivating maize with complementary organic and inorganic fertilizers gives a comparable cob yield as inorganic fertilizer and has nutrients higher than from sole organic fertilizer application.Key words: Maize, Fertilizer type, Nutrient uptake

Estimation of the carrying capacity of grazing land in the buffer zone of Katavi and Rukwa-lukwati conservation area in Mpanda district

This study was conducted in the village land of the buffer zone of South Katavi National Park and the north-western area of the Rukwa-Lukwati Game Reserve, both in Mpimbwe Division, Mpanda District. The study area is characterized by gently undulating hills on the Ufipa plateau between the eastern and western branches of the East African Rift of between 800 and 1000 m above sea level. The area experiences a sub-humid type of climate with medium to high rainfall of between 800 mm in the south and 1200 mm north. Characteristic vegetation is open miombo woodland in most of the area and brash wood, scrubs and tall grass in the rest. In the early 1970’s, many immigrant Sukuma from Shinyanga and Tabora regions with their large numbers of cattle and goats moved into the area in search of good pastures and water for their livestock. Being agro-pastoralists, the immigrants also cleared bush and trees for cultivation. This practice triggered soil erosion, land pressure and social conflicts between the immigrants, local people and conservators. The Katavi- Rukwa Conservation and Development Programme (KRCD), was formed in March 1990, to address the problems through “Community Based Conservation” Approach. One of the first step in these approach was to determine the carrying capacity of the grazing land including all potential feed resources in the village land around wildlife protected areas, in order to determine the number of livestock to be retained in the area without negatively affecting conservation efforts. The study revealed that the Dry matter yield (DMY) from natural pastures was 3.54 tones ha-1yr-1 and the Potential Dry Matter (PDM) production from crop residues was 33.130 tons ha-1 yr-1, the total area under grazing was 49,197ha, the total feed resource potentially available for livestock = 205,320 tons yr-1 and the estimated carrying capacity was 1 TLU: 0.63 ha or 1 LU: 1.26 ha. The herbage production potential of 3.54 tones ha-1 yr-1 obtained in this study is within the range of 0.5-10.0 tons ha-1 yr-1 reported elsewhere in East Africa bearing in mind the diversity of ecosystems. The inclusion of crop residues in carrying capacity computation has resulted in a relatively higher value of 1 TLU:063 as compared to reported figures. In agro-pastoral systems, crop residues constitute a significant part of the feed resource. Before any decision to remove livestock in conflict areas is made, it is important to estimate the carrying capacity in order to accurately predict the maximum number of livestock to be sustainably maintained in the area. Key Words: Carrying capacity - feed resources - crop residues agro-pastoralism - community based conservation - buffer zone.

Effects of crop rotations on carrot yield and on the nematodes Pratylenchus penetrans and Meloidogyne hapla

Carrot yield (Daucus carota) and population levels of the root-lesion nematode Pratylenchus penetrans and the northern root-knot nematode Meloidogyne hapla were measured in five rotation crops and in subsequent carrot crops at three field sites (1998-1999, 1999-2000, and 2000-2001). Total and marketable carrot yields averaged over the three sites did not differ in the crop sequences but there was a difference among sites. The total yields at sites 1, 2, and 3 were 77.86, 68.12, and 30.33 tonnes ha-1, respectively. Marketable yields were 59.04, 60.62, and 24.11 tonnes ha-1 at sites 1, 2, and 3, respectively. The lower yields were attributed primarily to less rainfall during July and August in 2001, and possibly to northern root-knot nematodes that were more prevalent at site 3. Mean levels of root-lesion nematodes in soil were highest (2690 nematodes kg-1) in carrot that followed timothy (Phleum pratense cv. Common), lowest (1100 nematodes kg-1) in carrots that followed marigold (Tagetes erecta cv. Crackerjack), and intermediate after barley (Hordeum vulgare cv. Chapais), pearl millet (Pennisetum glaucum cv. Millet 101), and annual ryegrass (Lolium multiflorum cv. Lemtal). Root-lesion nematode populations were also lower in marigold than in the other crops. Northern root-knot nematodes were not detected in rotation crops. The study indicated that carrot yields did not differ irrespective of the previous crop, but root-lesion nematode populations in soil at harvest were highest in carrots that followed timothy and lowest in carrots that followed marigolds. Population levels of root-knot nematodes in carrots did not differ among the crop sequences.

Hydrologic and sediment responses to vegetation and soil disturbances

Soil erosion has been linked to stream sedimentation, ecosystem degradation, and loss of rangeland productivity. However, knowledge of soil loss, as it affects rangeland productivity or ecosystem sustainability is lacking. We evaluated the effects of 3 levels of vegetation cover reduction (0, 27%, and 43%) and soil removal (0, 12, and 24 tonnes ha-1) on soil surface runoff and sediment yield in a sagebrush [Artemisia tridentata var. vasseyana (Rydb.) Beetle] steppe under simulated rainfall. Time to runoff initiation was affected by the vegetation cover reduction treat- ments, but not by the soil removal treatments. The 43% vegeta- tion canopy reduction treatment resulted in a shorter time to runoff initiation than did the 27% and 0% canopy reduction treatments (p = 0.002). Results from analysis of covariance indicated that vegetation reduction and soil removal did not significantly affect sediment yield or runoff quantities in the first year following treatments. Multiple regression analysis revealed total sediment yield was related to forb cover, sand in the upper soil profile (0-5 cm), and the amount of bare ground. Time to runoff initiation was positively correlated with slope. Despite the lack of significant treatment differences, we do not conclude that these soil removal and vegetation reduction treatments had no affect on soil surface hydrology and sediment yield. There are numerous studies that show a strong relationship between vegetation reduction and soil erosion. Future research at this site may reveal long-term treatment effects that were not apparent in first year results.

Continuing Growth Response to Phosphate Fertilizers by a Pinus radiata Plantation over Fifty Years

Abstract The period of growth response of forest plantations to phosphate fertilizer applications has been variable and difficult to predict. Significant growth responses by Pinus radiata (D. Don) to two different phosphate fertilizers, superphosphate and rock phosphate applied at 96 kg P ha-1 (previously reported by the authors) have continued for the 50 yr period since the fertilizers were initially applied in 1947. There have been no further fertilizer applications. At the end of the second rotation of 33 yr (50 yr after the fertilizer was applied), the growth and biomass of the trees were determined, together with soil and foliage chemical analyses, and comparisons made with those obtained earlier. The standing volume of the phosphate treatments was 430 m3 ha-1, an increase of 50% over the 287 m3 ha-1 in the untreated control. Soil total phosphorus concentrations were increased from 64 mg kg-1 in the control to 105 mg kg-1 and 134 mg kg-1 in the superphosphate and rock phosphate treatments, respectively, and have remained constant. The aboveground biomass of the treated plots was about 380 tonne ha-1 compared with 278 tonne ha-1 in the control. The single application of phosphorus has led to a significant change in site characteristics. The implications for forest management are that a relatively low application of fertilizer on some nutritionally poor sites changes the productive capacity of the site. FOR. SCI. 48(3):556–568.

Effects of High Rates of Coal Fly Ash on Soil, Turfgrass, and Groundwater Quality

A field study (1993–1996) assessed the effects of applying unusually high rates of coal fly ash as a soil additive forthe turf culture of centipedegrass (Eremochloa ophiroides).In addition, the quality of the soil and the underlying groundwater was evaluated. A Latin Square plot design was employed to include 0 (control, no ash applied), 280, 560, and 1120 Mg ha-1 (mega gram ha-1, i.e., tonne ha-1)application rates of unweathered precipitator fly ash. The onceapplied fly ash was rototilled and allowed to weather for 8 months before seeding. Ash application significantly increasedthe concentrations in plant tissue of B, Mo, As, Be, Se, and Bawhile also significantly reducing the concentrations of Mg, Mn,and Zn. The other elements measured (i.e., N, K, Ca, Cu, Fe, Ag,Cd, Cr, Hg, Ni, Pb, Sb, Tl, Na, and Al) were not affected. Of these elements Mg, Cu, and Mo concentrations in plant tissue increased with time while B and Se decreased temporally. The diminution of B and Na appears to be related to the leaching ofsoluble salts from ash-treated soils. Of all the elements measured, only Mn produced significant correlation (p = 0.0001) between the tissue and soil extractable concentrations. Ash treatment elevated the soil pH to as high as 6.45 with theenhanced effect occurring primarily in the 0–15 cm depth. Soilsalinity increased with the application rate with the largestincreases occurring in the initial year of application. However,by the second year, most of the soluble salts had already leachedfrom the treatment zone into deeper depths, and by the fourthyear, these salts had completely disappeared from the profile.The chemical composition of the underlying groundwater was notadversely impacted by the ash application. Plant tissue and groundwater data however, indicate that much higher rates of fly ash can be used on this type of land use where the plant species is tolerant of soil salinity and does not appear tobioaccumulate potentially toxic trace elements.

Grain legumes and green manures as pre-rice crops in Northeast Thailand

Two field experiments were conducted on farmers' fields in Northeast Thailand to examine the potential of several green manure and short-duration grain legume species as pre-rice green manures. The performance of species mixtures was also investigated. Experiments were conducted under rainfed conditions both with and without recommended applications of lime, P and K fertilizers. 15N-isotope methods were used to estimate N2-fixation in the legumes and N supplied by the legume residues to a following rice crop. When provided with lime, P and K fertilizer, all legumes grew well and fixed 65–85% of their N, amounting to 59–102 kg N ha-1 wihin 90 days. The short-duration groundnut and a mixed Sesbania rostrata and multi-purpose cowpea treatment produced over 4 tonnes ha-1 residue dry weight which contained 135–150 kg N ha-1. In addition groundnut yielded almost 2 tonnes ha-1 of grain, whilst the intercrop yielded 1 t ha-1 of fresh pods of MCP, only 35% less than the sole MCP which only produced 41 kg N ha-1 in its stover. Rice dry weight increases of over 50% were found after several of the legume treatments, and 15N-based estimates indicated up to 18 kg N ha-1 was directly supplied by the legume stover to the rice. Without fertilizer application residue yields of the S. rostrata + multi-purpose cowpea mixed crop were poor (580 kg ha-1) and N2-fixation contributed only 57% of the N accumulated (20 kg N ha-1 fixed). The application of P and K fertilizers was found to approximately double residue yields with the combined addition of lime more than doubling these yields again, resulting in 88% of the legume N derived from N2-fixation (84 kg N ha-1). The following rice recovered 9–17% of the added legume N and the yield response in rice reflected the differences in legume yield. Application of P,K and lime resulted in a fivefold increase in the amount of legume N recovered by rice, indicating the importance of alleviating nutrient deficiencies through fertilizer application if green manures are to be used successfully in Northeast Thailand.

Release Of Some Trace Elements From Sluiced Fly Ash On Acidic Soils With Particular Reference To Boron

The purpose of this study was to examine the relationship between the concentration of boron (B) and some other selected trace elements in soil solution as effected by hydrogen ion activity within the normal pH range for acidic soils commonly amended with agricultural limestone and, alternatively, alkaline fly ash. Sluiced alkaline fly ash was applied to an acidic, clay textured soil at rates equivalent to 0, 42, 84, 125 and 167 tonne ha-1 based on the soil lime requirement. After wheat was grown and harvested the soil-ash mixtures were maintained at field capacity moisture content for an additional 4 months before pore water samples were extracted by immiscible displacement. The total concentrations of Co, Cr, Fe, V and Zn in the ash treated soils increased by < 10% at the highest application rate of ash, the content of Cu was increased by 13% and B by 38%. Only the concentration of boron increased appreciably in the pore water extracts. Release of B from the ash was correlated with the solubility behaviour of Ca and Mg, and not with the dissolution of glass phases in the ash. Speciation and adsorption calculations for the extracts were carried out using the program MINTEQ. Common Ca, Mg and Na borate minerals were undersaturated with respect to the equilibrated solutions. Application of the constant capacitance model to the adsorption of B on mineral surfaces suggested that adsorption had little effect on total dissolved B at pH values below 6.0. Predicted concentrations of B in solutions, equilibrated with calcite in a subsurface horizon, were up to 10.6 mg dm-3; more than double the recommended maximum concentration for B (5mg dm-3) in potable water in Ontario.

Release of Some Trace Elements From Sluiced Fly Ash On Acidic Soils With Particular Reference To Boron

The purpose of this study was to examine the relationship between the concentration of boron (B) and some other selected trace elements in soil solution as effected by hydrogen ion activity within the normal pH range for acidic soils commonly amended with agricultural limestone and, alternatively, alkaline fly ash. Sluiced alkaline fly ash was applied to an acidic, clay textured soil at rates equivalent to 0, 42, 84, 125 and 167 tonne ha-1 based on the soil lime requirement. After wheat was grown and harvested the soil-ash mixtures were maintained at field capacity moisture content for an additional 4 months before pore water samples were extracted by immiscible displacement. The total concentrations of Co, Cr, Fe, V and Zn in the ash treated soils increased by &lt; 10% at the highest application rate of ash, the content of Cu was increased by 13% and B by 38%. Only the concentration of boron increased appreciably in the pore water extracts. Release of B from the ash was correlated with the solubility behaviour of Ca and Mg, and not with the dissolution of glass phases in the ash. Speciation and adsorption calculations for the extracts were carried out using the program MINTEQ. Common Ca, Mg and Na borate minerals were undersaturated with respect to the equilibrated solutions. Application of the constant capacitance model to the adsorption of B on mineral surfaces suggested that adsorption had little effect on total dissolved B at pH values below 6.0. Predicted concentrations of B in solutions, equilibrated with calcite in a subsurface horizon, were up to 10.6 mg dm-3; more than double the recommended maximum concentration for B (5 mg dm-3) in potable water in Ontario.

Some Limitations of Sluiced Fly Ash as a Liming Material for Acidic Soils

Innovative methods are currently being sought to safely utilize and reduce the amount of sluiced fly ash stored in on-site facilities at thermal electric power facilities in Ontario, Canada. The objective of this study was to investigate the possibility of utilizing sluiced fly ash as a liming material on acidic soils. A greenhouse experiment was established to examine the influence of the ash on soil pH values and the yield and chemical composition of corn, soybeans, wheat and alfalfa grown on amended soil. The sluiced ash had an initial pH value of 9.1 (1:1 H2O) and contained an equivalent CACO3 content of 11.5% (+0.2%) based on total content of Ca and Mg in the ash. Fly ash was applied at rates of up to 167 tonnes ha-1 to samples of the surface horizon (0-15 cm) of an acidic clay textured soil found local to the power plant. Application of fly ash increased soil pH values but a high concentration of boron in the added ash limited plant growth. Results indicated that the sluiced ash could be used as a liming material at application rates of up to 110 tonnes ha-1, on acidic, clay textured soils provided boron tolerant crops such as alfalfa were grown. Further research is required to establish the potential for leaching of boron to ground water and to determine the potential for plant uptake of other trace elements such as As and Se.

Estimates of Carbon Storage in the Aboveground Biomass of Victorias Forests

The pool of carbon in the world's forests is of similar magnitude to that in the atmosphere, yet little attention has been given to improving measures of carbon in terrestrial biomass. Much of the critical data for forest biomass on which models of global carbon cycling rely is, in fact, based on the accurate sampling of less than 100 ha of forest. Uncertainties in biomass estimation at the local and regional level may be responsible for much of the current speculation as to unidentified sinks for carbon. We have used a forest inventory (i.e. records of forest volume obtained for harvesting purposes) approach to quantify the biomass of forests in Victoria, Australia. Forests were analysed by type, age and region. Regression equations were developed for the accumulation of biomass with age across all productivity classes for each forest type. The mean carbon density for above-ground components of Victorian native forests is 157 tonnes ha-1 (t ha-1), although forest types range in mean carbon density from 250 to 18 t ha-1. Pinus radiata D. Don plantations in Victoria have a mean carbon density of 91 t ha-1 in the above-ground components. Total carbon stored in above-ground biomass is estimated to be 1.2 X 109 t. Rates of carbon fixation vary with forest age, species and site. Mountain ash (Eucalyptus regnans F. Muell.) forests fix around 9 t of carbon ha-1 annually during the first few years of growth, decreasing to 6 t ha-1 by age 10. Rates of carbon accumulation by other forests are generally less than this and, at the lower end of the range, box-ironbark forests, mallee and woodlands accumulate between 0.5 and 2 t ha-1 year-1. P. radiata plantations in Victoria will accumulate around 7 t carbon ha-1 year-1.

Nitrogen and energy balance of a short-rotation poplar forest system.

The mean annual dry matter production of a short-rotation poplar forest in the Netherlands was 14.4 tonnes ha-1 during a 5-year growing period. During the growing period trees took up 542 kg N ha-1 of which 64 % was in the bole and branches. In the 5th year denitrification was measured in undisturbed columns in the field by the acetylene-inhibition technique. An annual denitrification rate of 18 kg N ha-1 was estimated on the basis of the observed N2O profile. The system needed an annual input of 122 kg N ha-1 to balance the nitrogen budget. The energy balance showed that at the present dry matter production the system had a net output of 54 GJ ha-1 year-1. An increase in dry matter production to a maximum of 25 tonnes ha-1 year-1, possible by planting the trees at a higher density, would raise the net energy output to 97 GJ ha-1 year-1, in spite of higher energy inputs associated with fertilizer applications. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Growth, yield and preliminary selection of seedling guavas in Queensland

Five guava seedlines of Hawaiian origin, namely GA9-37, GA12-1 6, GA10-48, GA11-56 and GA9-39 were yield tested in coastal sub-tropical south-eastern Queensland. The work demonstrated that seedling guavas produce attractive yields comparable with overseas countries. First crop mean yields were 30.72 kg/tree after 18 months in the field, demonstrating the precocious bearing of the guava. Yields for second and third cropping years were 45.6 and 77.9 kg/tree. These yields equate to 24.7, 37.2 and 61.5 tonnes ha-1 at a planting density of 805 trees ha-1. Third crop yields give the attractive gross returns of around $15,000 ha-1, at current prices paid by processors in Queensland. No differences were found between seedlines in annual yields, accumulated crop yields, fruit Number/tree, annual yield per unit cross sectional area of butt (an index of fruitfulness) and accumulated yield per unit cross sectional area of butt. Within seedline, variability masked differential response and these aspects are discussed. Fruit yields and relative increase in butt cross sectional area of butt varied with cropping year. Fruit. number per tree and yield per unit cross sectional area of butt varied with years, as did fruit number per kg (an index of fruit size). The latter also varied with seedlines. These effects were attributed to water rationing in spring of the second crop year. Preliminary selection based on fruit quality aspects of individuals identified four individuals which are undergoing detailed processing assessment, namely GA9-39R1T2, GA11-56T7, GA11-56R5T2 and GA1 1-56R5T1. Two further individuals were selected for fresh fruit market testing, namely GA11-56T3 and GA11 -56R1T1. We believe that market development rather than horticultural problems to be overcome will dictate the success of the guava as a crop for Australia, since the guava is comparatively easy to grow and manage.

Preliminary experiments on the growth of kenaf (Hibiscus cannabinus) for paper pulp production in the Ord Irrigation Area, Western Australia

The results of agronomic studies with kenaf (Hibiscus cannabinus) grown for paper pulp production in the Ord Irrigation Area, Western Australia, are described. There were two experiments: one with cv. C2032 in which growth of the crop was studied at four seeding rates, two row spacings and four times of sowing, and a second in which the growth of cv. Guatemala -4 was followed at two times of sowing. It was demonstrated that year-round growth could be sustained with irrigation. A peak dry-matter yield of 25.6 tonnes ha-1 was achieved after 240 days from a July sowing of Guatemala -4. The yields of stem material from cv. C2032 increased as seeding rate was increased from 5 to 20 kg ha-1. Dry matter yields were higher with a narrow row spacing than with a wide row spacing; total dry matter production from crops sown on 1.5 m beds grown with 5 rows spaced 20 cm apart was 17 per cent higher than from single rows sown on 1 m ridges. The effect of row spacing was mainly in the yield of tops and foliage and there was no significant effect on stem yields. Data are given of the uptake of essential nutrients by kenaf crops. which illustrate the large quantities of nutrients removed by the crop. Ratooning of kenaf is shown to be possible provided it is cut at least 10 cm above ground level. The percentage of plants recovering after cutting increased as the height of cut was increased from 10 cm to 30 cm above ground level.

Plant Biomass, Primary Production and Bioelements of Three Mature Beech Forests in South Sweden

Three mature forests representing a vegetational gradient of South Swedish beech forests are described in terms of the distribution of organic matter and bioelements. Biomass and primary production were estimated from allometric regressions made on sampled trees. Biomass, in the order Mercurialis, Lamium and Deschampsia-types, was 358, 375 and 263 tonne ha-1. Corresponding total primary production was 19.0, 17.8 and 12.3 tonne ha-', and the above ground production was 16.7, 15.4 and 10.6 tonne ha:yr1, with yearly increments in biomass estimated at 10.8, 11.0 and 7.1 tonne ha-' yr'. There was a relative increase of the root system in the high-low productivity gradient. Soil variables such as organic matter, N, nitrification rate, C/N-ratio, pH, amount of exchangeable nutrients and soil water change along the gradient and affected the chemical composition of the trees. N and K in the current twigs were positively correlated with primary production but there was a negative correlation for P, Si and Mn. Decomposition rates and transformation factors for most elements are decreasing along the high-low productivity gradient. A general allometric regression equation, with diameter and height as independent variables, seems capable of describing the total plant biomass of both highand low-productive beech forests in South Sweden.

Effects of sowing time and sowing density on the growth of subterranean clover at Adelaide

Growth curves have been constructed for undefoliated swards of subterranean clover (cv. Woogenellup) established at three plant densities (1,2 and 4 x l03 plants per m2) at three times of the year (May, June and August). The swards grew without any apparent water stress, until early December. The time course of shoot dry matter increase is examined by the use of a logistic function and by the recognition of three growth stages. Maximum crop growth rates ranged from 10 to 15 gm-2 day-1. The rate decreased with increase in density but increased with lateness of sowing, so that the highest crop growth rate was obtained with the lowest plant density sown in August. Estimated end-of-season yields were independent of density but decreased from about 1500 g m-2 for May sowing to 1000 g m-2 for August sowing. Effects of sowing density on the growth pattern persisted throughout the whole season. Swards took 70–100 days to attain a leaf area index (LAI) of 3, after which crop growth rates were almost constant with time and independent of short-term fluctuations in the level of daily solar radiation and average daily temperature. Swards reached a maximum LAI of about 6, LAI being linearly related to the amount of shoot dry matter up to about 600 gm-2 independent of density and sowing time. No evidence was found of an optimal relationship between crop growth rate and LAI.It is concluded that end-of-season yield is independent of plant density above 1000 established plants per m2, and that swards established as late as August have the capacity to attain a yield of 10 tonnes ha-1 provided the growing season is extended.

Grain yield and flowering of some introduced grain legumes in South Australia

Data are presented for time of flowering, total shoot dry weight and grain yield of White Brunswick pea (Pisum sativum), six introduced peas and one introduction each of Lathyrus sativus and Lathyrus cicera from ten plot experiments conducted in South Australia over the period 1955-1 960.None of the introduced legumes flowered earlier than White Brunswick peas and only one, possibly, has a greater capacity for higher grain yield. L. cicera on the other hand gave 25 per cent greater yield over all sites and seasons with an average of 2.84 tonne ha-1.The ratio between grain yield and total shoot dry weight varied with genotype and between seasons with a genotype. A low ratio was not always associated with low dry matter production.