Estimation of the above-ground biomass of the herb layer in forest communities

The paper deals with the estimation of maximum above-ground herb-layer biomass in selected forest communities of the Malé Karpaty Mts., (Lesser Carpathians) SW. Slovakia. Use was made of a combined method of indirect sampling and phytocenological relevés, and the following values were ascertained: 41 kg/ha in theLuzulo-Fagetum (276 kg/ha if mosses included), 691 kg/ha in theCarici pilosae-Carpinetum, 364 kg/ha in theDentario-Fagetum, 476 kg/ha in theAceri-Carpinetum, and 1364 kg/ha in theStellario-Alnetum. The results are discussed and compared with earlier data published in the literature.     

Leaf-litter and changing nutrient levels in a seasonally dry tropical hardwood forest,Belize, C.A.

Summary Total above ground plant biomass in a 45 year old seasonally dry tropical hardwood forest was estimated to be approximately 56,000 kg/ha oven dry weight. Nutrients immobilized in the standing vegetation were: N, 203 kg/ha; P, 24 kg/ha; K, 234 kg/ha; Ca, 195 kg/ha; Mg, 47 kg/ha; Na, 9 kg/ha; Mn, 1 kg/ha; Cu, 0.5 kg/ha; Zn, 3 kg/ha; Fe, 4 kg/ha. Total nutrients returned each year through the litter were: N, 156 kg/ha; P, 9 kg/ha; K, 59 kg/ha; Ca, 373 kg/ha; Mg, 32 kg/ha; Na, 5 kg/ha; Mn, 1 kg/ha; Al, 21 kg/ha; Zn, 0.3 kg/ha; Fe, 9 kg/ha. Half of the nutrients immobilized in the standing vegetation were found in the leaves and are returned annually to the soil. Although litter fall is interrupted during the year, the mean nutrient content of the litter was high –5.2%.A decomposition rate of 0.48 percent per day was considered high for a seasonally dry tropical hardwood forest. Fluctuations in soil nutrient levels showed a sharp increase at the start of the rainy season. Later during the dry season nutrient levels decreased to concentrations similar to what they were just prior to the rainy season. Soil organic matter levels were very high –20% in the top 12 cm.     

Agronomic evaluation of prospective new crop species. VI.Briza humilis—Source of galactolipids

Briza humilis Bieb., a low seed-yielding member of the family Gramineae, showed agronomic promise as a commercial source of galactolipids. The seed lipid contains about 80% galactolipids, compared to little, if any, in other evaluated species ofBriza. An obligate winter annual,B. humilis is a small, noncompetitive grass with good seed retention. Seed (caryopsis) yields ranged from 280 to 1,475 kg/ha. Clean threshing of the light-weight seed (0.5 g/1,000) proved difficult. Because yield and plant size varied, agronomic improvement should be possible.     

Effects of NPK fertilisation in arid southern Mongolian desert steppes

Few studies have been performed on the importance of nutrient availability for plant productivity at <200 mm annual precipitation and available meta-analyses have produced contradicting results. Here, we present data from a 3-year experiment on the effects of NPK-fertilisation under ambient precipitation in dry Central Asian steppes. The study site had an annual mean precipitation of ca. 160 mm and represented an intensively grazed montane desert steppe. One year of NPK-fertilisation at levels equivalent to 10 and 20 gN/m² (100 and 200 kg/ha) increased above-ground mean standing crop in a moist year to 1130 and 1490 kg dry mass/ha, respectively, compared to the 615 kg/ha from the control. The absolute increase was smaller in subsequent drier years, but the crop again more than doubled under fertilisation. The effects were most pronounced for the main fodder plants Agropyron cristatum and Allium polyrrhizum, which benefited from fertilisation more than other less palatable species. Both species also showed increased levels of foliar N. Fertilisation enhanced flowering activity on the community level, and soil analyses revealed that nutrients accumulate in the soil. Effects are therefore expected to be long lasting. Our results imply that nutrient shortage may co-limit plant growth at well below 200 mm annual precipitation. Considering that predominantly nomadic land use is known to result in nutrient withdrawal, our data raise concerns of a largely unnoticed potential pathway to pasture degradation.     

The response ofPinus caribaea mor. var. Hondurensis seedlings to nitrogen,phosphorous and potassium fertilizers

Summary A soil pot culture experiment was conducted to study the response ofPinus caribaea var. hondurensis seedlings to the N, P, K fertilizers in a 3³ factorial combination of nutrients in four replicates. For this purpose, seedlings were grown in plastic pots in soils collected from Bahau pine experimental area. These soils belong to Durian series and are generally poor in nutrients.The seedlings were supplied with 112 kg/ha, 336 kg/ha and 560 kg/ha (100 lb/ac, 300 lb/ac and 500 lb/ac) of N, P, K in solution form in all possible combinations. Periodic growth measurements were taken and dry matter production was estimated at the conclusion of the experiment.The results indicate that phosphorous is the most important nutrient for the height growth of seedlings. The absolute height increment under the best treatment combination (N₁P₃K₁) was about threefolds (25.7cm) compared to 8.8 cm in the control. It was also found that higher levels of N and K, though not beneficial to height growth, resulted in better radial growth and more dry matter production compared to control plants. However, highest levels of N and K in the present experiment produced inhibitory influence as regards height growth even in the presence of low level of phosphorous.The study indicates that application of phosphorous at least at the rate of 560 kg/ha per plant is necessary on this type of soil to boost the initial height growth ofPinus caribaea var. hondurensis. Nitrogen at the rate of 336 kg/ha and potassium at the rate of 112 kg/ha will induce better radial growth.     

Vegetable oil replacements for petroleum oil adjuvants in Herbicide sprays

The objectives of this research were to observe plant response to vegetable oil sprays and to learn if vegetable oils — sunflower, soybean, linseed, or camelina — can replace petroleum oil as an herbicide adjuvant. Vegetable oils were sprayed on grain sorghum [Sorghum bicolor (L.) Moench.] and sunflower (Helianthus annuus L.) at 4 7 L/ha and were neither harmful nor beneficial to the crops. When used as an adjuvant postemergence with 1.68 kg/ha of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], 2.3 L/ha of vegetable oil were as effective in weed control as either 2.3 or 9.4 L/ha of petroleum oil. All atrazine treatments gave complete control of dicotyledonous weeds. But vegetable oil adjuvants with atrazine at 1.68 kg/ha gave significantly more grass weed control than atrazine alone at 2.24 kg/ha in two of five trials and were equally good in the other trials. The cost of the adjuvant is less than that of the atrazine replaced, and the initial herbicide residue in the soil is reduced by 25%.     

Effects of seeding rate and plant density on sclerotinia stem rot incidence in canola

Abstract

Sclerotinia stem rot (Sclerotinia sclerotiorum Lib. deBary) affects canola wherever it is grown. Seeding rates, which are believed to affect the microclimate beneath the canopy, were evaluated for their impact on sclerotinia stem rot incidence. A study with five seeding rates (2.2 kg/ha, 3.3 kg/ha, 6.7 kg/ha, 13.3 kg/ha and 20.0 kg/ha) and four canola cultivars chosen for their variation in canopy structure and lodging resistance was conducted in Carman, Manitoba, Canada, in 2001 to 2003. A significant relationship between sclerotinia stem rot disease incidence (DI) and seeding rate was found. With an increase in seeding rate, the DI was significantly increased in the mean of the canola cultivars, and individually, only in the lodging-prone cultivar AC Excel. Lodging significantly increased for all cultivars when seeding rates exceeded the standard 6.7 kg/ha. Multiple regression analysis revealed that both plant density and lodging explain the majority of the variation in DI. Both plant density and lodging resistance varied in having a larger influence on DI depending on the year and cultivar analysed. Our results indicate that increasing seeding rate does modify the microenvironment and increases the potential for lodging, which may be responsible for plant-to-plant spread of this disease.     

Trichoderma spp. and Bacillus spp. as growth promoters in maize (Zea mays L.)

Microbes that are beneficial to plants are used to enhance the crop growth, yield and are alternatives to chemical fertilizers. Trichoderma and Bacillus are the predominant plant growth-promoting fungi and bacteria. The objective of this study was select, characterize, and evaluate isolates of Trichoderma spp. and Bacillus spp. native from the northern region of Sinaloa, Mexico, and assess their effect on growth promotion in maize (Zea mays L.). In greenhouse conditions, four Trichoderma isolates and twenty Bacillus isolates, as well as two controls, were tested in a completely randomized design with three replicates. We selected the two best strains of Trichoderma and Bacillus: TB = Trichoderma asperellum, TF = Trichoderma virens, B14 = Bacillus cereus sensu lato and B17 = Bacillus cereus, which were evaluated in the field in a completely randomized blocks in factorial arrangement design with three replicates applying different rates of nitrogen fertilizer (0, 150 kg N/ha, and 300 kg N/ha). Treatments 5 (B17 = B. cereus) and 11 (TF = T. virens) both fertilized with 150 kg N/ha showed similar yields and they did not reveal significant differences from the treatments fertilized with 300 kg N/ha. This indicated that treatment 5 (B17= B. cereus with 150 kg N/ha) and treatment 11 (TF= T. virens with 150 kg N/ha) were efficient as growth promoters, by not showing significant differences in root volume and dry weight of foliage. The results indicated a reduction of 50% in the rate of nitrogen to fertilizer required for maize (Zea mays L.) crops. These microorganisms Trichoderma and Bacillus could be an alternative to reduce the use of chemical fertilizers in maize.     

Contribution of organic matter,N and P through roots and stubbles in irrigated rice culture

Summary A study was conducted on the quantities of crop residues (stubbles) recycled into the soil after harvest with 2 early and 3 medium duration varieties of rice under irrigated culture. The addition of crop residues depended linearly on the total dry matter production of the plants. Dry matter (DM) of stubbles and the N content of the same showed a linear trend. The relationship between grain yield and N contribution through stubbles fitted to a linear regression. In early types the maximum N recycled is 16 kg/ha at an yield range of 4 to 6 t/ha while in medium types a maximum of 26 kg N/ha is recycled at the same yield level. The relationships between DM of stubbles and ‘P’ content of the stubbles and between grain yield and ‘P’ content of stubbles also turned out to be linear. The P content varied from 1 to 4 kg/ha in early types and 1 to 2 kg/ha in medium group. More N was recorded in the stubbles of the medium group while more P was found in the early duration varieties. There were clear varietal variations and the results were discussed in the light of the current literature.     

Integrated agroforestry systems improve soil carbon storage,water productivity,and economic returns in the marginal land of the semi-arid region

Environmental crises, land degradation, and frequent crop failure threaten the livelihoods of millions of the populace in the semi-arid agroecosystems. Therefore, different combinations of annual crops with perennial fruit trees were assessed to restore the soil carbon, and enhance farm productivity and profitability in a semi-arid climate. The study hypothesized that the integration of perennial fruit trees with seasonal crops may enhance farm productivity, economic returns, and environmental sustainability. Integration of phalsa (Grewia asiatica) with mung bean (Vigna radiata) - potato (Solanum tuberosum) system recorded the highest system productivity (25.9 Mg/ha) followed by phalsa with cowpea (Vigna unguiculata) -mustard (Brassica juncea) systems (21.2 Mg/ha). However, Karonda (Carissa sp.) with mung bean - potato system recorded maximum net return (3529.1 US$/ha), and water use efficiency (33.0 kg/ha-mm). Concerning the benefit-cost (B:C) ratio, among the agroforestry systems, the karonda + cowpea - mustard system registered a maximum BC ratio (3.85). However, SOC density remained higher (9.10 Mg/ha) under the phalsa + cowpea - mustard and Moringa + mung bean - potato system (9.16 Mg/ha) over other systems. Similarly, phalsa + mung bean - potato system had the highest C sustainability index (27.6), carbon sequestration potential (0.6–0.67 Mg/ha/year), and water use efficiency (33.0 kg/ha-mm). Hence, the study suggested that the integration of short-duration leguminous and oilseeds with fruit trees offer a myriad of benefits and an efficient system for restoring the soil C without compromising the food and livelihood security of the rural populace in semiarid regions.     

Meloidogyne Incognita Management using Fumigant and Non-fumigant Nematicides on Sweet Potato

Southern root-knot nematode (SRKN, Meloidogyne incognita) is a major pest of sweet potato, and nematicides are needed to manage this nematode. The objectives of this study were to assess the efficacy of fluazaindolizine, a new non-fumigant nematicide, in comparison with the fumigant nematicide 1,3-dichloropropene (1,3-D) and non-fumigant nematicides fluopyram and oxamyl for (1) SRKN management, (2) impacts on free-living nematodes, and (3) sweet potato yield in field trials. Among all nematicides, 1,3-D at 84 kg/ha most consistently (2 of 3 years) managed SRKN soil populations and improved yield. Fluazaindolizine at 2.24 kg/ha and fluazindolizine at 1.12 kg/ha plus oxamyl at 2.14 kg/ha managed SRKN populations and improved yield in 1 of 3 years, whereas fluazaindolizine alone at 1.12 kg/ha only decreased SRKN populations. Fluopyram at 238 g/ha did not affect SRKN or yield. Nematicide application also had non-target effects on free-living nematodes with 1,3-D reducing abundances relative to untreated most frequently (2018 and 2020), but other nematicides also reducing free-living nematode abundances in 2020. In summary, 1,3-D is the most consistent option for SRKN control on sweet potato, but fluazaindolizine, oxamyl or combinations of the two products can also be effective.     

Soybean Yield as Related to Rates of 1,3-Dichloropropene Applied at Planting for Management of Root-Knot Disease

1,3-Dichloropropene (1,3-D) at rates of 17.2 to 51.6 liters/ha applied 3 days preplant or at planting significantly (P < 0.05) reduced the amount of galling on roots of soybean grown in sites infested with Meloidogyne incognita or M. arenaria. Populations of M. incognita second-stage juveniles at harvest were significantly (P < 0.05) reduced by all treatments. Only the 51.6-liters/ ha treatments and a 3-day preplant 34.4-liters/ha application significantly reduced at-harvest juvenile infestations of M. arenaria. Equations (P < 0.001) relating soybean yield and 1,3-D dosage indicated soybean phytotoxicity at the upper range of the nematicide rates. The maximum yield response was predicted at 40 liters/ha applied 3 days preplant at both infestation sites. Maximum yield response was predicted with 30 liters/ha applied at planting to M. incognita-infested soil and from 25 liters/ha applied at planting to M. arenaria-infested soil. Application of economic factors suggested that management of M. incognita may be cost effective with at-plant treatments of low rates of 1,3-D. Yield responses of M. arenaria-infected soybean exposed to similar treatments were insufficient to justify their use at prevailing prices.     

Uncommon vascular plant species in an East-Central Swedish forest area-a comparison between young and old stands

Abundance of uncommon vascular plant species (indicator species and red-listed species) was recorded in 120 circular (12.6 m²) random plots in young (10–24 years after deal-cutting) and old (>80 years) forest stands, respectively, in the forest area of Vällen (2 600 ha), ca. 80 km north of Stockholm, Sweden. Factors describing stand density, field-layer and soil moisture were recorded. A total of 16 species were observed and of these 14 were found in old and 9 in young stands. Seven species occurred exclusively in the old stands and two in the young stands. The total number of species records was significantly higher in young than in old stands, 80 and 71, respectively. Mean number of records per ha was ca. 530 for the young stands and ca. 470 for the old. Of the five species common enough to be tested, a difference was only found for Paris quadrifolia , which was significantly more frequent in young than old stands. Galium odoratum, Hepatica nobilis, Lathyrus vernus and Paris quadrifolia grew in significantly more sheltered sites, e.g. beneath other herbs and grasses or close to shrubs and trees in young compared to old stands. Nested subset analysis showed that the whole data-set had a nested structure. Galium odoratum was significantly nested and thus indicated rich plant assemblages. In this calcareous area with nutrient-rich forest soils, there evidently is a potential for at least some uncommon vascular plant species to survive the phases following clearcutting. The study indicates that green-tree retention at final fellings and avoidance of heavy shrub removal during cleaning are beneficial to the flora.     

The effect of stem and cob borers on maize subjected to different nitrogen treatments

The influence of four nitrogen levels (0, 60, 90 and 120 kg N/ha) on growth of maize and development of lepidopterous pests was investigatdd in a field trial. Nitrogen had a positive effect on both plant growth variables (plant height, stem diameter and yield), and development and survival ofSesamia calamistis andEldana saccharina, and thereby increased the incidence of dead hearts and stem tunneling. However, the percent yield loss due to artificial infestation decreased with increasing N application rate from 20% to 11% in the in the 0kg/ha and 120kg/ha treatment, respectively. Using a multiple regression analysis, plant height, plant diameter and stem tunneling were found to be the most important variables explaining the variability in maize yield.     

A new approach to determine the total airborne N input into the soil/plant system using 15N isotope dilution (ITNI): results for agricultural areas in Central Germany

The atmospheric deposition of nitrogen (N) in the environment is of great concern due to its impact on natural ecosystems including affecting vegetation, reducing biodiversity, increasing tree growth in forests, and the eutrophication of aquatic systems. Taking into account the average annual N emission into the atmosphere in Germany of about 2 million t N (ammonia/ammonium, NOx), and assuming homogeneous distribution throughout Germany, an average N deposition of 45 kg/ha x year can be calculated. Such high atmospheric N deposition could be confirmed by N balances from long-term field experiments in Central Germany (e.g., the Static Fertilization Experiment in Bad Lauchstdt). By contrast, estimates by standard methods indicate a deposition of only about 30 kg N/ha x year. This is because the standard methods are using wet-only or bulk collectors, which fail to take into account gaseous deposition and the direct uptake of atmospheric N by aerial plant parts. Therefore, a new system was developed using 15N isotope dilution methodology to measure the actual total atmospheric N input into a soil/plant system (Integrated Total Nitrogen Input, ITNI). A soil/plant system is labeled with [15N]ammonium-[15N]nitrate and the total input of airborne N is calculated from the dilution of this tracer by N from the atmosphere. An average annual deposition of 64 +/- 11 kg/ha x year from 1994-2000 was measured with the ITNI system at the Bad Lauchstdt research farm in the dry belt of Central Germany. Measurements in 1999/2000 at three other sites in Central Germany produced deposition rates of about 60 kg/ha x year. These data clearly show that the total atmospheric N deposition into the soil/plant system determined by the newly developed ITNI system significantly exceeds that obtained from standard wet-only and bulk collectors. The higher atmospheric N depositions found closely match those postulated from the N balances of long-term agricultural field experiments.     

Assessment of the losses caused to potatoes by the potato cyst nematodes, Globodera rostochiensis and G. pallida

Nine field trials were carried out from 1967 to 1973 on sandy loam soils in Staffordshire and Worcestershire to study the relationship between potato yield and numbers of potato cyst nematodes (Globodera spp.). Three (probably five) of these trial sites appeared to be infested with G. rostochiensis only, whereas both species occurred on the remaining four sites which grew the resistant variety, Maris Piper. Although mixtures of the two species occurred on some plots they tended to have different distributions within each trial site. The results from this work have been analysed, together with those from earlier work in the Eastern Counties on peat and silt soils, over two population density ranges, 0–40 eggs/g (5 sites) and 0–160 eggs/g (16 sites). There is no evidence of any difference in the regression of yield on eggs/g amongst the five sites in the lower range (b =–0.90 + 0.11) nor amongst 15 of the 16 sites in the higher range (b = -0–40 ± 0–02). Analysis of 10 sites with sufficient data in the 40–160 eggs/g range gave b = -0.24 ± 0.06. Thus the regression lines are essentially parallel for each of the two ranges, covering several potato varieties, soil textures and different potential yields and suggest that the varieties used are equally tolerant. The losses are 6.25 t/ha/20 eggs/g for the 0.40 eggs/g range, 1.67 t/ha/20 eggs/g for the 40–160 eggs/g range, and 2.75 t/ha/20 eggs/g as a mean for the whole range. A maximum loss of 22 t/ha is indicated. Peat soils are less dense than mineral soils but there was no need for adjustment in nematode counts. Losses caused by potato cyst nematodes are better expressed as actual yield losses rather than as percentage decreases.     

Study of the Effect of Phosphorus on Mineral Nutrition of Faba Bean « Vicia fabae L.»

Our study focuses on the study of the phosphorus efficiency on the mineral nutrition of a leguminous plant; to study this efficiency, we tested the effect of increasing doses of phosphorus on the mineral nutrition of faba bean and on the concentration of Nt (total nitrogen), Pi (available phosphorus), KE (exchangeable potassium), C (organic carbon), and the organic matter (OM) rate in the rhizospheric soil after harvest, as well as the concentration of N, P, K, Na, and Ca in the roots, stems, leaves, and seeds of faba bean. The faba bean crop was subjected to four phosphorus doses (P0?=?0 kg/ha; P1?=?70 kg/ha; P2?=?140 kg/ha; P3?=?210 kg/ha). The main results obtained showed that the concentration of the mineral elements in the different faba bean parts reacted differently to the phosphorus treatments. Regarding the dosage of nutrients in the different parts of the faba bean, the results obtained highlight that Pi deficiency in the soil does not only affect phosphate nutrition but can also affect the absorption of other mineral elements, a synergy is recorded between the K concentration in the roots and in the stems with the organic carbon in the soil, and an antagonism between K and Na in the different parts of the plant. All the results obtained in this work show that a phosphate fertilization for doses between 70 kg/ha and 140 kg/ha of P2O5 improves the microbial life of soil microorganisms.

     

Exchange of N2O and CH4 between the atmosphere and soils in spruce-fir forests in the northeastern United States

We measured the exchange of N₂O and CH₄ between the atmosphere and soils in 5 spruce-fir stands located along a transect from New York to Maine. Nitrous oxide emissions averaged over the 1990 growing season (May–September) ranged from 2.1 ug N₂O-N/m²-hr in New York to 0.4 ug N₂O-N/m²-hr in Maine. The westernmost sites, Whiteface Mtn., New York and Mt. Mansfield, Vermont, had the highest nitrogen-deposition, net nitrification and N₂O emissions. Soils at all sites were net sinks for atmospheric CH₄ Methane uptake averaged over the 1990 growing season ranged from 0.02 mg CH₄-C/M²-hr in Maine to 0.05 mg CH₄-C/m²-hr in Vermont. Regional differences in CH₄ uptake could not be explained by differences in nitrogen-deposition, soil nitrogen dynamics, soil moisture or soil temperature. We estimate that soils in spruce-fir forests at our study sites released ca. 0.02 to 0.08 kg N₂O-N/ha and consumed ca. 0.74 to 1.85 kg CH₄ C/ha in the 1990 growing season.     

Nitrogen fixation by Myrica gale root nodules Massachusetts wetland

Summary Nitrogenase activity was measured by acetylene reduction in excised Myrica gale nodules collected throughout the growing season at two sites associated with a small lake in central Massachusetts. One site was in an open, weakly minerotrophic peatland dominated by M. gale and the other was on the lakeshore. Nitrogenase activity appeared in late May when the leaves unfolded, reached a peak in July when the maximum number of leaves was present, and declined until it was no longer measurable in late October several days after all leaves had fallen. Summer activities were substantially higher at the peatland site than the lakeshore. Maximum activities were 19.8±1.9 and 8.1±0.7 mol/h x g dry weight (x±SE; N=20) at the peatland and lakeshore sites respectively.Nitrogenase activities were very low at 5° C and increased linearly from 10 to 30° C, the highest temperature examined. The maximum soil temperature measured was 20° C, and no significant diurnal fluctuation in activity was detected.Annual nitrogen fixation calculated from the seasonal nitrogenase activity curve was 34 kg N/ha x yr at the peatland site with mean dry weight nodule biomass of 104 kg/ha, and 24 kg N/ha x yr at the lakeshore with 111 kg/ha nodule biomass. These rates of nitrogen fixation are equivalent to 4–5x the amount of nitrogen contained in bulk precipitation and are major components in the nitrogen budgets of the M. gale plants and wetlands in which they grow.     

Icacina oliviformis (Icacinaceae): A close look at an underexploited crop. I. Overview and ethnobotany

Icacina oliviformis is an underexploited, suffrutescent, savannah pyrophyte used for its edible seeds, tuberous roots, and fruit mesocarp in many areas of west and north-central Africa. The large seeds provide a relied-upon resource in Senegal, Guinea-Bissau, and the Central African Republic at the end of the dry season when food reserves in the villages are at their lowest annual levels. The tuberous roots, sometimes weighing over 50 kg, provide a rich source of starch in times of famine. This species deserves consideration for use in extensive agroforestry schemes in savannah habitats of west-central Africa.