Search

Soil seed bank is a reservoir for passive restoration of rangelands following bush clearance. This study was conducted to assess the effects of bush clearance on the seed bank size, composition, diversity and relationship between soil seed bank (SSB) and above ground vegetation (AGV) in Springbokvlakte thornveld. The study was conducted at Radi communal rangeland, Makapanstad in North-West Province, South Africa with an average rainfall of 459 mm annum−1. The rangeland was encroached at an average density of 6908 woody plants ha−1 by Vachellia tenuispina, Vachellia tortilis, Ziziphus mucronata and Asparagus laricinus, with V. tenuispina accounting for 92% of the woody cover. All woody plants within 50 × 25 m plots were mechanically cut using manual saws and loppers followed by chemical stump treatment using picloram. The cleared and their adjacent uncleared microsites were marked in the middle of a large shrubland and were protected from grazing. Soil samples were collected at three depths (0–10, > 10–20 and > 20–30 cm) in April (pre-treatment), August, October, December 2016 and, April and August 2017 in bush cleared and uncleared microsites. SSB was determined using the seedling emergence method. Vegetation surveys were conducted in February 2016 (pre-treatment) and 2017 (post-treatment). Thirty-seven species from 16 families emerged from the SSB. Perennial species were the most abundant life-form until December 2016, after which annuals increased to 70 and 71% in April and August 2017, respectively in cleared microsites. Eragrostis lehmanniana, Jamesbrittenia aurantiaca and Aristida bipartita were the most abundant species until December 2016, thereafter; Brachiaria eruciformis dominated by 55–61% from April to August 2017 in cleared microsites. Principal component analysis (PCA) revealed that most seed bank species correlated strongly with total soil nitrogen, C:N ratio and nitrates. Total seed densities remained similar from August to December 2016, thereafter; they were 2- to 3-fold higher in cleared compared to uncleared microsites. Seed densities declined significantly (p

Conservation agriculture (CA) is a sustainable management system that optimises yield while reducing input costs. However, reduction in tillage intensity and frequency as practised under CA general...

The Department for International Development of the United Kingdom, National Research Fund of South Africa and the International Foundation for Science.

SUMMARYThe short term nutrient supply of Leucaena leucocephala, Calliandra calothyrsus, Acacia angustissima and Acacia karoo prunings with or without supplemental inorganic nitrogen were tested using rape (Brassica napus L.) in a field trial. Prunings were applied at a rate of 5 t ha−1 to soil, alone or with supplemental N at 37.5 kg N ha−1 (¼ of recommended N). The respective decomposition and N release constants of the prunings were 9.15 and 9.70% for L. leucocephala; 6.15 and 6.40 for A. angustissima; 4.50 and 4.90 for C. calothyrsus; and 2.20 and 2.10 for A. karoo. These constants were best described by the (lignin+polyphenol)-to-nitrogen ratio of the prunings. Total biomass over the two seasons ranged from 1.40 to 17.28 t DM ha−1 and total growth rates ranged from 2.34–26.70 g plant−1 week−1. The cumulative N recovery at week 9 ranged from 21.1–66.1 %. Legume tree leaves can be used as a source of N for vegetable production. Farmers who use high tannin leaf litter are recommended to supplement with mineral N in order to assure adequate N availability during plant growth.

We examined the nutritive value of common grass species in the semi-arid rangelands of Borana in southern Ethiopia using local experience based herbage preference (LEBHP) perception and laboratory techniques. Local pastoralists in the study area were asked to identify common grass species and rank them according to the species’ preferences and palatability to cattle. The pastoralists listed a total of 15 common grass species which were then sampled during the main rain and cold dry seasons and analyzed for crude protein (CP), Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF) and ash content to verify pastoralists’ claim regarding the quality of individual species. The relative feed value (RFV) and dry matter digestibility (DMD) were also calculated using NDF and ADF contents. Spearman’s rank correlation was used to examine possible relationships between laboratory results and pastoralists’ experience on grass quality. Cenchrus ciliaris, Chrysopogon aucheri, Digitaria milanjiana, Eragrostis papposa and Panicum maximum were the top five species based on LEBHP perception. There were indications of inconsistency in terms of LEBHP perception among the different pastoral communities. The chemical composition of all grass species showed significant (p

Non-wood fibres are increasingly being used in the pulp and paper industry to help meet the increasing world demand for paper. Their use also helps to reduce demand on declining forest reserves. In this study several warm season grasses, prairie sandreed (Calmovilfa longifolia (Hook.) Scribn.), cordgrass (Spartina pectinata L.), big bluestem (Andropogon gerardii Vitman), and switchgrass (Panicum virgatum L. cv. Pathfinder (PF) and New Jersey 50 (NJ50)), were evaluated as potential raw materials for pulp and paper production. Raw material chemical composition, kraft pulp yield and properties, and fibre characteristics were evaluated. All these grasses were easily pulped under a mild kraft process, with pulp yields ranging from 44 to 51%, highest yields were recorded for NJ50 and big bluestem; and kappa numbers ranging from 10 to 16. The weight-weighted fibre length ranged from 1.29 to 1.43 mm, the highest value being recorded for big bluestem. The unbeaten pulp freeness ranged from 275 ml for sandreed to 411 ml for NJ50. Sandreed, NJ50 and big bluestem had high tear indices of 7.49, 7.12 and 7.07 mN m2 g−1, respectively. Cordgrass and sandreed had burst indices above 5.0 kPa m2 g−1 (5.68 and 5.22 kPa m2 g−1, respectively). Other physical and strength properties are also presented.

Switchgrass (Panicum virgatum L.) is one of several warm-season grasses that have been identified as potential biomass crops in North America. A two-year field study was conducted, on a free-draining sandy clay loam (St. Bernard, Typic Hapludalf), to characterize the growth and evaluate changes in biomass accumulation and composition of switchgrass at Montreal, QC. Three cultivars, Cave-in-Rock, Pathfinder, and Sunburst, were grown in solid stands in a randomized complete block design. Canopy height, dry matter (DM) accumulation and chemical composition were monitored biweekly throughout the growing season. Average maximum canopy heights were 192.5 cm for Cave-in-Rock, 169.9 for Pathfinder, and 177.8 for Sunburst. The respective end-of-season DM yields were 12.2, 11.5, and 10.6 Mg/ha. Biomass production among cultivars appeared to be related to time of maturation. Nitrogen concentration of DM decreased curvilinearly from 25 g/kg at the beginning of the season to 5 g/kg DM at season's end. Both acid-detergent fiber (ADF) and neutral-detergent fiber (NDF) concentrations increased to a maximum early in the season, after which no changes were detected. The average maximum values of ADF and NDF were, respectively, 647.6 and 849.0 g/kg DM for Cave-in-Rock, 669.1 and 865.2 for Pathfinder, and 661.8 and 860.9 for Sunburst. Changesmore » in canopy height, DM accumulation, and chemical composition could all be described by predictive regression equations. These results indicate that switchgrass has potential as a biomass crop in a short-season environment.« less

Adapted warm season grasses have potential for both summer forage and biomass production in eastern Canada. A field study was conducted in 1995 and 1996 to determine the response of switchgrass (Panicum virgatum L.) cv. Cave-in-Rock, Pathfinder, and Sunburst to nitrogen (N) fertilization at 0, 75, or 150 kg ha -1 and three harvest schedules in a short season area. The grass was harvested at 4- or 6-wk intervals or left uncut until the end of the season. These treatments were combined in a split-plot design in each of three blocks on a St. Bernard sandy clay loam (Typic Hapludalf). Herbage yield and herbage N concentration were determined at each harvest for the cutting schedules. Herbage yields revealed a cultivar × N × harvest schedule interaction in 1996, while in 1995 only the two-way interactions between cultivar × harvest schedule and N × harvest schedule were evident (P 6-wk > 4-wk with their respective mean yields being 11, 10, and 8 Mg ha -1 for Cave-in-Rock; 10, 8, and 6 Mg ha -1 for Pathfinder and 11, 8, and 7 Mg ha -1 for Sunburst. Nitrogen concentrations increased with fertilization and varied with harvest and year, but not with cultivar. Mean N concentrations were 12.4, 13.9, and 15.4 g kg -1 dry matter (DM) for the 0, 75, and 150 kg ha -1 N levels, respectively, under the 4-wk system. Corresponding values were 10.1, 11.6, and 12.9 g kg -1 for the 6-wk system. End of season N concentrations for the uncut regime averaged 5.4, 6.0, and 7.6 g kg -1 DM in increasing order of N fertilization. The results indicate that switchgrass has potential in both grazed or hay forage systems in eastern Canada.

Chlorophyll meters have been used to estimate leaf chlorophyll content, and therefore nitrogen (N) status and fertilization requirements for several crops. However, until now C4 forage grasses have not been investigated in this regard. A field study was conducted in 1995 and 1996 to evaluate the potential of chlorophyll (SPAD) meter readings to determine switchgrass N concentration and herbage yield. Meter readings were taken on the top most fully expanded leaves of switchgrass grown on a free draining sandy clay loam soil (St Bernard, Typic Hapludalf) fertilized at 0, 75, or 150 kg N ha‐1. The switchgrass was either cut at the end of the season or every four or six weeks. Herbage N concentration in uncut stands declined with time while SPAD readings increased to a mid‐season maximum, beyond which they declined rapidly. The relationship between N concentration and SPAD readings was linear (r2=0.62–0.93; p

Switchgrass ( Panicum virgatum L.) has been identified as a potential biomass crop in North America. A two-year study was conducted to characterize leaf area development and estimate radiation-use efficiency (RUE) of switchgrass in eastern Canada. Three cultivars, Cave-in-Rock (CIR), Pathfinder (PF) and Sunburst (SB) were grown in solid stands in a randomized complete block design. Dry matter (DM) yield, leaf area development and light interception were monitored bi-weekly throughout the growing season. Herbage subsamples were hand separated into leaf and sheath-stem fractions. Mean seasonal maximum leaf area indices (LAI) were 6.1, 5.3 and 5.1 for CIR, PF and SB, respectively. By early July of each season the canopies were intercepting about 90% of the incoming light. End of season DM yields were 12.2, 11.5 and 10.6 Mg ha −1 for CIR, PF and SB, respectively. The stem plus leaf sheaths constituted the major component of DM and its accumulation trend parallelled that of total DM. End of season stem-sheath components averaged 764, 714 and 691 of the total g kg −1 DM for CIR, PF and SB, respectively. Energy contents of the switchgrasses averaged 17.4 MJ g −1 DM and did not vary among cultivars or during the season. This translated into total energy yields ha −1 of 216 GJ for CIR, 197 for PF and 186 for SB. Radiation-use efficiencies computed using total incoming solar radiation, for the near linear growth phases, averaged 1.07 g DM MJ −1 for CIR, 0.90 for PF and 0.89 for SB. The respective values based on photosynthetically active radiation were 2.20, 2.00 and 1.96 g DM MJ −1 . Changes in LAI, relationships between LAI and light interception and DM yield could all be described by predictive regression equations. These results indicate the potential of switchgrass as a biomass crop in short season areas.

Field studies were conducted in 1994 and 1995 to determine the phenology, leaf and tiller characteristics and yield of 22 warm-season grasses in south western Quebec, Canada. Cordgrass (Spartina pectinata L.), two cultivars of Indiangrass [Sorghastrum nutans L. (Nash)], two cultivars of big bluestem (Andropogon gerardii Vitman), 12 cultivars of switchgrass (Panicum virgatum L.) and five cultivars of prairie sandreed [Calamovilfa longifolia (Hook) Scribn., were included in the study. In terms of initial spring growth, CWNC (cordgrass) and New Jersey 50 (switchgrass) were the earliest and latest, respectively. Initial spring regrowth from sandreeds was predominantly from continued growth of biennial tillers, from rhizomes in cordgrass and from buds on stem bases for the other species. The earliest maturing entries were ND3743, Dakota, Ottawa3 (switchgrasses) and Bison (big bluestem). New Jersey 50 and CWNC were the latest maturing. CWNC had high tiller numbers throughout the season while the rest of the entries showed increases in tiller numbers in summer. There were significant differences among entries in height development across the season. Biomass yields ranged from 65 to 861 g per plant. Lignocellulose concentration was high in all entries with neutral detergent fiber (NDF) and acid detergent fiber (ADF) ranging from 770–860 g kg−1 and 460–540 g kg−1, respectively. Nitrogen and ash concentrations ranged from 4–10 and 40–70 g kg−1, respectively. The results indicate potential for cordgrass (CWNC) and several switchgrasses for biomass production in the short season areas of Quebec.

Cool spring and early summer temperatures have limited the adoption of warm season grasses in northern environments like eastern Canada. This study characterized the performance of nine switchgrass (Panicum virgatum L.) populations ('Blackwell', 'Cave-in-Rock', 'Dakota', 'Forestburg', 'New Jersey 50', 'Pathfinder', 'Sunburst', 'Shelter', and 'ND3743') in southwestern Quebec. These populations were evaluated for 3 yr on a St. Bernard sandy clay loam (Typic Hapludalf) near Montreal. Leaf area development patterns during the season fitted second degree polynomial models, increasing with time after planting and decreasing in the fall. Maximum leaf area index (LAI) ranged from 6.1 to 8 m 2 m -2 , with Cave-in-Rock and New Jersey 50 having the highest LAIs. The populations had different vertical leaf area distributions. For Blackwell, Cave-in-Rock, and Shelter, more than 50% of the leaf area was in the top third of the canopy. New Jersey 50 and Pathfinder had uniform vertical leaf area distributions through the canopy. Light extinction coefficients (k) ranged from 0.57 to 0.72. Average end-of-season biomass yields were 8477, 9943 and 10 869 kg ha -1 in 1993, 1994, and 1995, respectively. The relationship between end of season yield and leaf area duration was linear. Cave-in-Rock, New Jersey 50, and Blackwell produced the greatest yields. All entries had high neutral detergent fiber (NDF) [810-870 g kg -1 dry matter (DM)] and acid detergent fiber (ADF) (510-570 g kg -1 DM). Nitrogen and ash concentrations ranged from 3.2 to 8.2 and 47 to 66 g kg -1 DM, respectively. This study showed that switchgrass can be successfully grown in southwestern Quebec.

A field study was conducted in the fifth (cowpea crop) and sixth (sorghum crop) seasons of a long-term conservation agriculture trial at Matopos Research Station to determine the effect of tillage, maize mulch rates and intensity of hoe weeding on weed density and community diversity. The experiment was a split-plot randomized complete block design with three replications. Tillage was the main plot factor; conventional tillage versus the minimum tillage (MT) systems of ripper tine and planting basins. Maize mulch rate (0, 4 and 8 t ha-1) was the sub-plot factor to which was super-imposed the intensity of hoe weeding treatment (low and high) as from the fifth season. Tillage system had no significant (P