Frequent Harvesting Research Articles

Characteristics of Biomass Allocation and Root Distribution of <i>Halogeton glomeratus</i> under Different Rainfall Conditions

Water is the limited factor in arid and semi-arid regions. Precipitation, as the sole source of water replenishment in arid area, plays an important role in sustaining the desert ecosystem. With the trend of global warming, precipitation is increasing in arid region recently, especially in the extremely arid region at the south rim of Tarim Basin. Halogeton glomeratus (Bieb.) C. A.Mey is the key species of Gobi desert at the south rim of Tarim Basin, which use the scarce and irregular rainfall for survival in greatest possible. There was little research on characteristics of H. glomeratus involving biomass allocation and root distribution under different rainfall conditions in extremely arid regionsItalic text. Our objective was to study the response for H. glomeratus to the global precipitation change. Artificial controlling water supply was conducted at three levels in experimental fields in Cele Gobi desert. Additionally, the natural precipitation control plot was analyzed for comparison. Frequent harvests were used to determine the response of biomass allocation and root distribution of H. glomeratus during a growing season under extreme rainfall conditions. Biomass of H. glomeratus increased as rainfall increased in the prophase of the growing season, but decreased in the later half phase of the growing season. Biomass allocation showed no significant difference among the treatments. However, H. glomeratus with higher level of rainfall allocates more biomass to roots. H. glomeratus adapts to the lower water condition by means of modulating roots distribution with deeper vertical main root and extent horizontal lateral roots.

Lignocellulose modifications by brown rot fungi and their effects, as pretreatments, on cellulolysis

Brown rot fungi Gloeophyllum trabeum and Postia placenta were used to degrade aspen, spruce, or corn stover over 16weeks. Decayed residues were saccharified using commercial cellulases or brown rot fungal extracts, loaded at equal but low endoglucanase titers. Saccharification was then repeated for high-yield samples using full strength commercial cellulases. Overall, brown rot pretreatments enhanced yields up to threefold when using either cellulase preparation. In the best case, aspen degraded 2weeks by G. trabeum yielded 72% glucose-from-cellulose, a 51% yield relative to original glucan. A follow-up trial with more frequent harvests showed similar patterns and demonstrated interplay between tissue modifications and saccharification. Hemicellulose and vanillic acid (G6) or vanillin (G4) lignin residues were good predictors of saccharification potential, the latter notable given lignin’s potential active role in brown rot. Results show basic relationships over a brown rot time course and lend targets for controlling an applied bioconversion process.

The effectiveness of conservation measures to enhance nest survival in a meadow bird suffering from anthropogenic nest loss

The main reason for meadow bird declines is supposed to be the intensification of grassland management with earlier first harvest dates and more frequent harvests, resulting in high nest destruction rates. To increase productivity of meadow bird populations in intensified grassland areas a delay of mowing date and individual nest protection measures have been proposed. However, for ground-nesting songbirds such as the whinchat (Saxicola rubetra) the effectiveness of such measures remains widely unknown. In particular, if nest predation rate is high, measures to protect nests from agricultural destruction alone might be questionable. Here, we quantify whinchat nest survival of (1) unprotected nests situated in early mown meadows, (2) protected nests situated in early mown meadows, and (3) nests situated in late mown meadows. Analyses considered the fact that successful and unsuccessful nests are not found with equal probabilities. Periods of reduced nest survival were associated with mowing periods in the different types of meadows. In early mown meadows nest survival rates were low (S<0.1), and both conservation measures, individual nest protection and delayed mowing, resulted in significantly increased nest survival rates (S>0.7). Individual nest protection cannot avoid changes in habitat quality of intensively managed meadows, and therefore is only suitable as small-scale and short-term measure to increase nest success until a high portion of late mown meadows is established. Thus, we suggest that a combination of the two measures applied to intensified grassland fields should be provided to maintain viable sizes of endangered meadow bird populations.

Effect of spacing on Biomass production, Nutrient content and uptake by Poplar (Populus Deltoides) plantations

Among exotic tree species, Poplar (Populus deltoides) is a winter deciduous tree species, which produces maximum litter in a single flush for maintaining soil fertility of plantations through its decomposition and release of nutrients and are chosen primarily for their capacity to achieve high growth rates and wood production over a wide range of sites. Besides these, the short rotation cycle of plantation has one major problem of depletion of nutrients that is caused by frequent harvest of plant, which leaves the site unfertile as a huge quantity of nutrients are removed. Keeping these points in view, the present study was conducted to estimate the biomass production and nutrient removal by eight years old Poplar plantation raised at different spacing in a replicated randomized block design having three spacing of 5 x 4 m, 10 x 2.5 m and 15 x 2.5 m in research area of Department of Forestry, C CSHAU Hisar. Biomass of all the plant parts decreased with increasing tree spacing except that the differences between 10 x 2.5 m and 15 x 2.5 m spacing in respect of leaves and branches biomass were not significant. The total tree biomass including litter fall was higher in 5 x 4 m (415 t/ha) followed by 10 x 2.5 m (330 t/ha) and 15 x 2.5 m (192 t/ha) spacing. Concentration of both primary and secondary nutrients in different plant parts differed significantly at different spacing. Maximum nutrient concentration was recorded in leaves at 15 x 2.5 m spacing. However, Poplar stem accounted for maximum uptake of all the nutrients. Among poplar spacing, closer tree spacing of 5 x 4 m recorded maximum uptake of both primary and secondary nutrients except that K and Mg uptake was maximum at 10 x 2.5 m spacing.

Production and economic effects of in-pond grading of channel catfish

Periodic grading and harvesting of fish has been shown to increase production of some species by removing larger fish throughout the growing season, reducing overall biomass, and increasing growth of smaller fish. Two two-year studies measured production and economic effects of the UAPB grader as compared to traditional live car grading and assessed effects of frequent harvesting and grading. Multi-batch production systems were used in both studies. In Study 1, fingerlings grew significantly better in ponds graded with the UAPB grader (0.97 g d −1) as compared to the traditional live car (0.80 g d −1) and resulted in 14% fewer under-sized (<0.57 kg) fish sent to the processor. In Study 2, increased frequency of harvest up to four harvests a year resulted in significantly fewer over-sized fish (>1.51 kg), more frequent receipt of revenue, and improved cash flow. Economic analysis showed that: (1) it was economically advantageous for catfish farmers to switch to the UAPB grader under a variety of farm size and processor dockage scenarios; and (2) increasing the frequency of harvest up to four harvests/year resulted in fewer over-sized fish, less dockage at the processing plant, improved cash flow, and more favorable economic outcomes.

Forage Quality Management of Kura Clover in Binary Mixtures with Kentucky Bluegrass, Orchardgrass, or Smooth Bromegrass

Kura clover (Trifolium ambiguum M. Bieb.) is a potentially useful perennial legume because of its excellent nutritive value and persistence under environmental extremes. However, information about forage quality of kura clover - grass mixtures adapted to the North-Central USA is limited. Objectives of this research were to determine forage nutritional value of kura clover-grass mixtures under different harvest frequency and cutting height regimes. 'Rhizo' kura clover was grown alone and in binary mixtures with 'Park' Kentucky bluegrass (Poa pratensis L.), 'Comet' orchardgrass (Dactylis glomerata L.), and 'Badger' smooth bromegrass (Bromus inermis Leyss.) at the Arlington Agricultural Research Station located near Madison, WI. Three harvest frequencies (, , or annually) and two cutting heights (4- or 10-cm) were imposed on each binary mixture and on kura clover grown alone. Higher nutritive value was observed in the binary mixtures with more frequent harvest and lower cutting height. Averaged over 3 years and all harvest frequency and cutting height treatments, the nutritive value of the Kentucky bluegrass and smooth bromegrass mixtures was superior to that of the orchardgrass mixture ( NDF and CP in the Kentucky bluegrass mixture; NDF and CP in the smooth bromegrass mixture; NDF and CP in the orchardgrass mixture). All of the mixtures and harvest management systems evaluated in this study produced forage with quality equivalent to grade one alfalfa hay and suitable for highproducing livestock, even though the highest quality was observed in the Kentucky bluegrass mixture with harvesting at the shorter cutting height.

Sixty Years of Management on a Small Longleaf Pine Forest

Abstract In 1948, the US Forest Service set aside a 40-ac tract on the Escambia Experimental Forest in South Alabama to demonstrate longleaf pine (Pinus palustris Mill.) management for the small landowner. At that time, the management goal for this “Farm 40” was to produce high-quality poles and logs on a 60-year rotation. The goal was to be accomplished entirely through management of the existing natural forest, with little to no capital investment other than the cost for prescribed burning, marking trees for cut, and limited control of cull hardwoods. Management of the forest has continued making the Farm 40 an excellent demonstration of small-scale longleaf pine management. Frequent harvests and small capital outlay continues to make this type of management strategy especially appealing to today's landowners with limited resources.

Commercialization unsustainable to Himalayan environment

Indigenous people of north western Himalayan region of India utilize a wide range of biological resources for subsistence. The age-old practices of resource utilization have supported the rural economy with equity and social justice and conservation of resources since generations. However, in recent times, due to market demand, the biological resources are subjected to premature and frequent harvesting of ruthless exploitation by unskilled people particularly from outskirt of people. In addition to this, unfavorable government forest policy and ignoring people’s participation in decision-making and changing climatic conditions are some of the prime factors responsible for changing traditional resource management practices. Over increasing population pressure demand lead for market oriented commercial demand has resulted in over-exploitation of some of the plant resources at alarming pace. This calls for the development of resource management techniques built up on traditional knowledge capable of meeting the challenges of conservation on the one hand and socio-economic development of the local people on the other. Changing indigenous resource management practices in north western Himalaya imperils herbal based health care system and livelihood pattern.

Bahiagrass Tiller Dynamics in Response to Defoliation Management

ABSTRACTNew bahiagrass (Paspalum notatum Flügge) genotype PCA Cycle 4 is more productive than existing bahiagrass cultivars during the cool season, but it may not persist as well when defoliated frequently or to short stubble. Characterizing tiller dynamics forms a basis for understanding mechanisms of grass yield and persistence responses to defoliation. A 2‐yr field experiment studied the effects of two stubble heights (4 and 8 cm) and two harvest frequencies (7 and 21 d) on tiller dynamics of diploid (PCA Cycle 4, ‘Pensacola’, and ‘Tifton 9’) and tetraploid (‘Argentine’ and Tifton 7) bahiagrass. Tiller number of highly persistent Argentine and Pensacola was unaffected by defoliation treatment and generally greatest among cultivars. Tiller number of Tifton 9 and PCA Cycle 4 varied by up to 970 and 730 tillers m−2, respectively, among defoliation treatments and was greatest with frequent harvests at short stubble. PCA Cycle 4 tiller mass was relatively low. Net tiller appearance rate was positive in spring and early summer, and was nearly zero or negative throughout the remainder of the growing season. This study showed that Tifton 9 and PCA Cycle 4 responded to frequent, close defoliation by increasing tiller number, but tiller mass was the least or not different from the least among entries tested. Very small tillers may indicate a weakening stand under frequent, close defoliation, and management practices such as rotational stocking may be necessary for PCA Cycle 4 to persist.

How increasing levels of private land enrollment in conservation agreements affect the population viability of grassland birds

There is a growing recognition that to effectively conserve biodiversity efforts have to extend into the realm of engaging private landowners. Agricultural lands have been particularly attractive targets for integrating conservation and production goals. Changes in hayfield management associated with agricultural intensification, including earlier and more frequent harvests, have a severe impact on grassland birds. Government-administered conservation incentive programs benefit grassland birds by delaying harvest dates on enrolled land to allow nesting pairs to successfully fledge at least one brood during the breeding season. In contrast, hayfields that are mowed during the breeding season support sink populations and may function as ecological traps. We examined the effect of increasing levels of hayfield enrollment on grasshopper sparrow population viability using a spatially-explicit, stage-structured, stochastic model of a grasshopper sparrow metapopulation in an urbanizing region of New Jersey. The probability of metapopulation extinction (POE) decreased as the proportion of enrolled hayfields increased and fell below 10% when about half of all available agricultural land was enrolled. POE also decreased with increasing numbers of enrolled hayfields most likely because hayfield enrollment removes a sink population from the landscape in addition to creating a source population. Our results are encouraging as they demonstrate that extinction risk for this grassland-dependent imperiled species can be reduced without having to protect or manage all remaining grassland habitat in the landscape.

Defoliation Management of Bahiagrass Germplasm Affects Dry Matter Yield and Herbage Nutritive Value

Bahiagrass (Paspalum notatum Flügge) cultivars are daylength sensitive and have minimal cool‐season production. A new bahiagrass breeding line is less daylength sensitive and more cold tolerant, but its dry matter (DM) yield and nutritive value responses to defoliation treatments are unknown. A 3‐yr field experiment studied effects of two stubble heights (4 and 8 cm) and two harvest frequencies (7 and 21 d) on diploids ‘Pensacola’, ‘Tifton 9’, and the less photoperiod‐sensitive, cold‐adapted (PCA) Cycle 4 bahiagrass; and the tetraploids ‘Argentine’ and Tifton 7. Stubble height had minimal effect on responses measured. When harvested every 7 d, Cycle 4 had the lowest and Argentine the greatest yield (8.4 vs. 11.8 Mg DM ha−1). When harvested every 21 d, Cycle 4 yield was similar to the other diploids (10.6 Mg DM ha−1) and less than the tetraploids (12.6 Mg DM ha−1). Cycle 4 yield distribution was similar to other diploids and generally greater in spring but less in summer than the tetraploids. Across defoliation treatments, Cycle 4 in vitro digestible organic matter (IVDOM) averaged 546 to 562 g kg−1 and was greater than all entries in 2006 and all but Tifton 9 in 2005. These data indicate that Cycle 4 was less productive than other bahiagrasses when harvested every 7 d during the warm season, as productive as other diploids at 21‐d harvest intervals, and slightly more digestible than other currently used bahiagrasses. Inferior yield under frequent harvest may imply less defoliation tolerance, thus persistence of PCA Cycle 4 should be studied further.

Impact of slash removal, drag scarification, and mounding on lodgepole pine cone distribution and seedling regeneration after cut-to-length harvesting on high elevation sites

Excessive slash loading could pose a problem for the regeneration of the serotinous lodgpole pine especially in forests at higher elevation where soil temperature is limiting. In the past, these forests have commonly been harvested using full-tree harvesting where trees are processed at roadside; however, recently cut-to-length harvesting has become a more frequent harvesting method. In cut-to-length harvesting the harvested trees are processed in the block, as a result slash accumulation is much higher on these cutblocks. In an experimental field trial, the cone distribution, natural lodgepole pine regeneration, and the growth and establishment of planted lodgepole pine were evaluated in response to slash load, drag scarification, and mounding after cut-to-length harvesting of high elevation lodgepole pine stands in the Rocky Mountains. Twelve sites were established, each contained six plots which were randomly assigned to six treatment combinations of two slash removal (slash and slash removed) and three mechanical soil preparation treatments (no soil preparation, drag scarifying, and mounding). The slash removal reduced slash volume by more than 50% but also reduced the number of lodgepole pine cones available for regeneration by over 33%. However, soil mechanical treatments offset this effect as fewer cones were necessary to achieve high natural pine regeneration densities. Drag scarification of plots resulted in 12 times the number of pine seedlings compared to the non-prepared plots. Although slash removal did not have an effect on the number of naturally regenerated lodgepole pine seedlings, it had a positive effect on their growth performance. Conversely, planted pine seedlings had lower mortality and better growth in soils that had been mechanically prepared and had the slash removed; however, the growth effects became only apparent 4 years after planting. While slash removal and mechanical soil preparation did increase soil temperatures; the slash removal treatment had a more transient effect on soil temperatures than soil preparation. Differences in soil temperature decreased over time which appeared to be mostly driven by a warming of the soils in the plots with no soil preparation, likely a result of the decomposition of the finer slash and feathermosses. Overall, it appears that surface disturbance on these high elevation sites had a far greater effect on lodgepole pine regeneration and growth than the increased accumulation of slash as a result of cut-to-length harvesting.

Yield and Species Composition of Binary Mixtures of Kura Clover with Kentucky Bluegrass, Orchardgrass, or Smooth Bromegrass

Kura clover (Trifolium ambiguum M. Bieb.) is a rhizomatous perennial legume that has potential as a forage crop in the North-Central USA because of its excellent persistence under environmental extremes. Little information is available about defoliation effects on productivity of mixtures of kura clover with grasses typically grown in this region. Two field trials were conducted to evaluate the effects of defoliation management on yield and species composition of binary mixtures of 'Rhizo' kura clover with 'Comet' orchardgrass (Dactylis glomerata L.), 'Badger' smooth bromegrass (Bromus inermis Leyss.), 'Park' Kentucky bluegrass (Poa pratensis L.), and solo-seeded kura clover near Arlington, WI. Three harvest schedules (three, four, or five times annually) and two cutting heights (4 or 10 cm) were imposed. Infrequent defoliation and lower cutting height produced significantly greater total forage yield, 6.6, 5.8, and 5.2 Mg/ha in 3-, 4-, and 5-harvest systems, respectively; and 6.5 and 5.2 Mg/ha for the 4- and 10-cm cutting height, respectively. Averaged over 3 yr and two environments, mixtures had higher forage productions than solo kura clover (6.3, 5.7, and 6.0 Mg/ha for the Kentucky bluegrass, orchardgrass, and smooth bromegrass mixtures, respectively; compared to 5.2 Mg/ha for solo kura clover). The proportion of kura clover in mixtures increased from yr 1 to yr 2 and was constant from yr 2 to yr 3 (34, 58, and 57%, respectively). We conclude that kura clover has excellent potential as a long-term component of grass-legume mixtures regardless of the cutting height, harvest frequency or grass species, even though the proportion of kura clover in harvested forage was significantly greater with less frequent harvest and shorter cutting height of all mixtures.

FISHING THE LINE NEAR MARINE RESERVES IN SINGLE AND MULTISPECIES FISHERIES

Throughout the world "fishing the line" is a frequent harvesting tactic in communities where no-take marine reserves are designated. This practice of concentrating fishing effort at the boundary of a marine reserve is predicated upon the principle of spillover, the net export of stock from the marine reserve to the surrounding unprotected waters. We explore the consequences and optimality of fishing the line using a spatially explicit theoretical model. We show that fishing the line: (1) is part of the optimal effort distribution near no-take marine reserves with mobile species regardless of the cooperation level among harvesters; (2) has a significant impact on the spatial patterns of catch per unit effort (CPUE) and fish density both within and outside of the reserve; and (3) can enhance total population size and catch simultaneously under a limited set of conditions for overexploited populations. Additionally, we explore the consequences of basing the spatial distribution of fishing effort for a multispecies fishery upon the optimality of the most mobile species that exhibits the greatest spillover. Our results show that the intensity of effort allocated to fishing the line should instead be based upon more intermediate rates of mobility within the targeted community. We conclude with a comparison between model predictions and empirical findings from a density gradient study of two important game fish in the vicinity of a no-take marine-life refuge on Santa Catalina Island, California (USA). These results reveal the need for empirical studies to account for harvester behavior and suggest that the implications of spatial discontinuities such as fishing the line should be incorporated into marine-reserve design.

Effects of fertilizer rates and cutting frequency on the marketable vegetable and pod yields in fluted pumpkin in southeastern Nigeria

Field plot studies were conducted on the effects of fertilizer rates and frequencies of cut on fluted pumpkin (Telfairia occidentatis) growth and yield parameters. Treatments comprised four levels of commercial N20P10K10 and four cutting intervals. These were laid out in a randomized complete block design with three replications. The experiment was conducted at Nsukka which is located at Latitude 060 52'N, longitude 070 24't, and on altitude 447.2m above sea level. The site was characterized as tropical ultisol of sandy loam texture. Frequent harvests of 2- and 4- weekly intervals yielded significantly (P < 0.5) higher marketable vegetable yield (leaf and shoot), and produced greater number of branches than lax or infrequent harvest of 6- or 8- weekly interval. Vegetable yield was increased with incremental application of N20 P10 K10 fertilizer rate. Marketable vegetable yield was best at 2- to 4- weekly interval of cut combined with 500 or 750 kg ha-1 of N20P10 K10 fertilizer rate. The 6- and 8- weekly intervals of cut significantly (P < 0.5) produced more pods than 2- or 4- weekly interval, but did not differ significantly from each other. A combination of 750 kg N20P10 K10 ha-1 with lax cutting of 8- weekly interval gave the highest number of pods and the greatest average weight of pods.Agro-Science Vol. 4 (1) 2005: pp. 66-69

Shift from non-pest to pest status in Rhopalomyia foliorum (Diptera: Cecidomyiidae), a species that induces leaf galls on Artemisia princeps (Asteraceae) cultivated as an edible plant in Okinawa, Japan

In 2003, many small ellipsoidal or spindle-shaped leaf galls were found on Artemisia princeps (Asteraceae) that had been cultivated as an edible crop plant in Okinawa Prefecture, Japan. The galls were similar to those induced by Rhopalomyia foliorum (Diptera: Cecidomyiidae) on Artemisia vulgaris in Europe and those attributed to an unidentified Rhopalomyia species on wild A. montana and A. princeps in Japan. The morphological features and molecular sequencing data indicate that the pest gall midge in Okinawa and the unidentified species are identical to R. foliorum, which is redescribed, with new biological information. The proportion of cultivated Artemisia plants that bore the leaf galls was 55.63–96.46%, a much higher proportion than on wild Artemisia. We consider that R. foliorum has shifted from non-pest to pest status in Artemisia fields under intensive cultivation that includes frequent harvesting of shoots and the application of rich nutrient fertilizer.

GRASSLAND SONGBIRDS IN A DYNAMIC MANAGEMENT LANDSCAPE: BEHAVIORAL RESPONSES AND MANAGEMENT STRATEGIES

In recent decades, earlier and more frequent harvests of agricultural grasslands have been implicated as a major cause of population declines in grassland songbirds. From 2002 to 2005, in the Champlain Valley of Vermont and New York, USA, we studied the reproductive success of Savannah Sparrows (Passerculus sandwichensis) and Bobolinks (Dolichonyx oryzivorus) on four grassland treatments: (1) early-hayed fields cut before 11 June and again in early- to mid-July; (2) middle-hayed fields cut once between 21 June and 10 July; (3) late-hayed fields cut after 1 August; and (4) rotationally grazed pastures. Both the number of fledglings per female per year and nest success (logistic-exposure method) varied among treatments and between species. Although birds initiated nests earlier on early-hayed fields compared to others, haying caused 99% of active Savannah Sparrow and 100% of active Bobolink nests to fail. Both the initial cutting date and time between cuttings influenced renesting behavior. After haying, Savannah Sparrows generally remained on early-hayed fields and immediately renested (clutch completion 15.6 +/- 1.28 days post-haying; all values are reported as mean +/- SE), while Bobolinks abandoned the fields for at least two weeks (mean clutch completion 33 +/- 0.82 days post-haying). While female Savannah Sparrows fledged more offspring per year (1.28 +/- 0.16) than female Bobolinks (0.05 +/- 0.05), reproductive success on early-hayed fields was low. The number of fledglings per female per year was greater on middle-hayed fields (Savannah Sparrows, 3.47 +/- 0.42; Bobolinks, 2.22 +/- 0.26), and late-hayed fields (Savannah Sparrows, 3.29 +/- 0.30; Bobolinks, 2.79 +/- 0.18). Reproductive success was moderate on rotationally grazed pastures, where female Savannah Sparrows and female Bobolinks produced 2.32 +/- 0.25 and 1.79 +/- 0.33 fledgling per year, respectively. We simultaneously conducted cutting surveys throughout the Champlain Valley and found that 3-8% of hayfield habitat was cut by 1-4 June, 25-40% by 12-16 June, and 32-60% by 28 June-2 July. Thus, the majority of grassland habitat was cut during the breeding season; however, late-hayed fields served as high-quality reserves for late-nesting female Bobolinks that were displaced from previously hayed fields. For fields first cut in May, a 65-day interval between cuts could provide enough time for both species to successfully fledge young.

Yield and Chemical Composition of Cassava Foliage and Tuber Yield as Influenced by Harvesting Height and Cutting Interval

A 3x4 factorial field experiment with a complete randomised split-plot design with four replicates was conducted from June 2002 to March 2003 at the experimental farm of the Nong Lam University, Ho Chi Minh City, Vietnam,to determine effects of different harvesting heights (10, 30 and 50 cm above the ground) and cutting intervals (45, 60, 90 and 285 days) on yield of foliage and tubers, and chemical composition of the foliage. Cassava of the variety KM 94 grown in plots of 5 m×10 m at a planting distance of 30 cm×50 cm was hand-harvested according to respective treatments, starting 105 days after planting. Foliage from the control treatment (285 days) and all tubers were only harvested at the final harvest 285 days after planting. Dry matter and crude protein foliage yields increased in all treatments compared to the control. Mean foliage dry matter (DM) and crude protein (CP) yields were 4.57, 3.53, 2.49, and 0.64 tonnes DM ha - 1 and 939, 684, 495 and 123 kg CP ha - 1 with 45, 60, 90 and 285 day cutting intervals, respectively. At harvesting heights of 10, 30 and 50 cm the DM yields were 4.27, 3.67 and 2.65 tonnes ha - 1 and the CP yields were 810, 745 and 564 kg ha - 1 , respectively. The leaf DM proportion was high, ranging from 47 to 65%. The proportion of leaf and petiole increased and the stem decreased with increasing harvesting heights and decreasing cutting intervals. Crude protein content in cassava foliage ranged from 17.7 to 22.6% and was affected by harvesting height and cutting interval. The ADF and NDF contents of foliage varied between 22.6 and 30.2%, and 34.2 and 41.2% of DM, respectively. The fresh tuber yield in the control treatment was 34.5 tonnes ha - 1 . Cutting interval and harvesting height had significant negative effects on tuber yield. The most extreme effect was for the frequent foliage harvesting at 10 cm harvesting height, which reduced the tuber yield by 72%, while the 90 day cutting intervals and 50 cm harvesting height only reduced the yield by 7%. The mean fresh tuber yield decreased by 56, 45 and 27% in total when the foliage was harvested at 45, 60 and 90 day cutting intervals, respectively. It is concluded that the clear effects on quantity and quality of foliage and the effect on tuber yield allow alternative foliage harvesting principles depending on the need of fodder for animals, value of tubers and harvesting cost. An initial foliage harvest 105 days after planting and later harvests with 90 days intervals at 50 cm harvesting height increased the foliage DM and CP yield threefold, but showed only marginal negative effect on tuber yield.

Forage Yield of Smooth Bromegrass Collections from Rural Cemeteries

Smooth bromegrass (Bromus inermis Leyss) is poorly adapted to management‐intensive rotational grazing because of slow and limited regrowth potential. In an effort to discover germplasm with tolerance to frequent cutting, smooth bromegrass plants were collected from fence and sod habitats of 30 rural cemeteries in Iowa, Minnesota, and Wisconsin. The objective of this study was to quantify, describe, and test the responses of paired fence and sod populations to different harvest frequencies. Thirty sod populations, 30 fence populations, and five cultivars were evaluated for season‐total forage yield and regrowth percentage at Arlington, WI, and Ames, IA. Three harvest managements were used, with mean harvest frequencies of four, five, or six harvests over 2002 and 2003. Fence populations had an average forage yield 5.5% higher than sod populations, a difference that was fairly consistent across harvest managements, test locations, and state of origin. Variation in linear responses to harvest management made up 65 and 77% of the harvest management × population interaction for forage yield and regrowth percentage, respectively. For seven cemetery sites, the sod population was better adapted than the fence population to a more frequent harvest management, as measured by a more stable response to harvest frequency (−2.02 ± 0.10 vs. −2.67 ± 0.12 Mg ha−1 harvest−1). For nine cemetery sites, the sod population had a higher increase in regrowth percentage with increased harvest frequency (15.8 ± 0.5 vs. 11.9 ± 0.7% units harvest−1). Smooth bromegrass germplasm from some cemetery sods appears to have potential value for developing tolerance to frequent defoliation.

Agronomic Performance of Timothy Germplasm from Forage and Turf Sods under Two Harvest Managements

Cultivated timothy (Phleum pratense L.) is an important grass for hay production in temperate North America. It is underutilized in management‐intensive rotational grazing systems because of its poor persistence when frequently defoliated. The objective of this study was to compare families selected for forage yield under frequent defoliation, families derived from old turf sods, and cultivars for agronomic performance under frequent and infrequent harvest managements (four vs. two harvests per year). Forage timothy was generally superior to turf timothy for most traits. Forage selections averaged 9.4 and 4.9% higher forage yield compared with cultivars under infrequent and frequent harvest managements, respectively, indicating that selection for higher forage yield under frequent harvest improved forage yield under both harvest frequencies. There were differences among the four types of turf (golf course fairways and roughs, cemeteries, and lawn/roadways), but these differences were not closely related to mowing height or frequency, perhaps because of the small sample size. Some turf collections ranked high for net herbage accumulation under frequent harvesting, but most turf collections were also characterized by a high frequency of regrowth panicles under either or both harvest frequencies. Timothy germplasm from old turf sods may have value in developing new timothy cultivars with improved tolerance to frequent defoliation and efforts should continue to gather and evaluate collections from a range of turf types and locations.