Response of tomato (Lycopersicon esculentum Mill.) growth to different phosphorous levels and sowing dates

A field trail was carried out at the University of Agriculture Peshawar during spring, 2013 in order to evaluate the effect of different levels of phosphorus fertilizer and various planting times on the growth and development of tomato. The main objective of the research work was to investigate the best sowing time for tomato in combination with suitable dose of P fertilizer in order to get maximum yield of tomato in the climatic conditions of Peshawar. RCB Design with split plot arrangements was used in the trail. The main factor (phosphorous levels of 0, 90, 110, 130) was allotted to main plots while sowing dates in sub plots. A total twelve treatment were replicated thrice. Maximum days to flowering (39.583?days) and fruiting (46.167?days) obtained in the late sowing. Minimum days to flowering (39), minimum days to fruiting (38.778?days) were taken by the early sowing. Maximum number of branches (27.778), maximum fruit length (6.0222), maximum fruit with (6.1667), maximum fruit yield (24.653?tons?ha^?1) was produced when the plot fertilize with 130?kg?P?ha^?1. Maximum number of fruit?plant^?1 (29.778) were produced with application of 130?kg?P?ha^?1, minimum number of fruits (23.667?cm), fruit width (3.778?cm), fruit length (4.3667?cm), plant height (56.300?cm) were obtained from the controlled treatment. Among the various treatment studied in experiment, it is concluded that early planting of the tomato in the summer season i.e. in the start of March and the use of higher dose of P (130?kg?P?ha^?1) is very beneficial for the excellent growth, development and yield of tomato crop.     

Groundwater influence on the water balance and nutrient budget of a small natural wetland in Northeastern Victoria,Australia

Despite the critical role of water movement in the nutrient dynamics of wetlands, few wetland studies of nutrient imports, exports and cycling have been based on comprehensive water balance studies. In particular, many investigations have underestimated the importance and role of groundwater movement. Nutrient loads entering and leaving a 2 ha reed swamp in the Kiewa Valley, North-east Victoria showed the swamp to be a nutrient source within the landscape under both base flow and storm flow conditions. During a dry period between February 1994 and January 1995 the wetland itself exported 230 kg of Total Nitrogen (115 kg ha⁻¹ yr⁻¹) and 24 kg of Total Phosphorus (12 kg⁻¹ ha⁻¹ yr⁻¹). Investigations confirmed that the wetland was a significant discharge area, and that groundwater accounted for 97% of the surface water and 50% of the Total Nitrogen and Total Phosphorus load leaving the system. A further 30% of Total Nitrogen and 26% of Total Phosphorus leaving the wetland was not attributable to rain/dust, surface water inputs or groundwater, and most likely resulted from the flushing of previously stored nitrogen and phosphorus. A fire which burnt most of the wetland area in September 1994 had little immediate impact on nutrient loads leaving the system. The study illustrates the complexity of assessing the nutrient dynamics and hydrology of natural wetlands, and raises questions with respect to the use of such systems for the interception of diffuse source nutrient loads within rural catchments.     

Integrated use of plant residues,phosphorus and beneficial microbes improve hybrid maize productivity in semiarid climates

Phosphorus unavailability and lack of organic matter in calcareous soils under semiarid climates are the major reasons for low crop productivity. A field experiment was conducted at The Agronomy Research Farm of The University of Agriculture Peshawar (semiarid climate), during summer 2015. The objective of the research was to investigate the effect of plant residues, organic and inorganic phosphorus management on improving yield and yield components of hybrid maize (CS-200) with (+) and without (?) phosphate solubilizing bacteria. The experiment was laid out in randomized complete block design with split plot arrangement, using three replications. A combination of plant residues and phosphorus sources were used as mainplot factor, and phosphate solubilizing bacteria were used as a subplot factor. The results revealed that plant residues, phosphorus sources and phosphate solubilizing bacteria significantly affected all parameters under study except number of plants at harvest. Application of legume residues (Faba bean) increased ear length (22.9 cm), grains row^?1 (46) and ear^?1 (419), 1000 grains weight (365 g), grain yield (6175 kg ha^?1) and shelling percentage (83) as compared to paper mulberry and garlic residues. Phosphorus application at the higher rate of 120 kg ha^?1 from inorganic source (single super phosphate) was superior in terms of higher ear length (24.4 cm), number of grains row^?1 (48) and ear^?1 (455), 1000 grains weight (380 g), grain yield (6558 kg ha^?1), harvest index (42.7%) and shelling percentage (83%) than the lower rate of phosphorus (60 kg P ha^?1). Inoculation of maize seeds with beneficial microbes (phosphate solubilizing bacteria) significantly increased ear length (22.9 cm), number of grains row^?1 (45) and ear^?1 (413), 1000 grains weight (364 g), grain yield (6237 kg ha^?1), harvest index (41.8%) and shelling percentage (82) than without seed inoculation. On the basis of our results from this study, we concluded that application of faba bean residues, 120 kg P ha^?1 as single super phosphate along with seed inoculation with phosphate solubilizing bacteria could improve yield and yield components of hybrid maize under semiarid climates.     

Variation in chemical composition of the River Frome, England, from 1965 to 1972

This study covers a 7-year period from 1965 to 1972, and shows the variation in flow, water chemistry and throughput of nutrients. The annual discharge of the River Frome varied considerably from year to year, ranging from a mean value of 4.48 m³ sec⁻¹ in 1971 to one of 8.38 m³ sec⁻¹ in 1966. The mean annual nutrient losses calculated over all 7 years of study from the River Frome catchment were: Nitrate 11.4 kg ha⁻¹, phosphorus 0.49 kg ha⁻¹ and potassium 8.4 kg ha⁻¹. There has been an increase in annual throughput (in years of similar flow) of 21% in phosphate and 41% in nitrate from 1965 to 1972.     

Canola and Oat Forage Potential Evaluation in Four Early Planting Dates

Canola and oat forage potential may be affected by climatic conditions when sown early. The objective of this study was to evaluate the forage canola and oat potential in four early sowing dates (September 11 and 25; October 9 and 23) during the 2012-2013 and 2013-2014 cycles in Matamoros, Coahuila, Mexico. Growth cycle duration, chemical composition, dry matter (DM), crude protein (CP), and net energy for lactation (NE_L) yields were determined. High temperatures and long photoperiods affected crops seeded on September 11, accelerating growth and reducing canola (26.6%-31.7%) and oat (15.8%) DM yields. As of September 25, canola cv IMC 205 reached DM yields (7746 kg ha^-1 -9276 kg ha^-1 ) similar to those obtained by oat (8115 kg ha^-1 -9507 kg ha^-1 ), while canola cv Hyola 401 obtained such yields only until October 23. Canola chemical composition was better than that found in oat, with higher CP, but lower acid detergent fiber (ADF) and neutral detergent fiber (NDF) contents. Canola equaled oat CP yields (972 kg ha^-1 -1215 kg ha^-1 ) in the first sowing date, while in the other three other canola sowings reached higher yields (1193 kg ha^-1 -1889 kg ha^-1 ). As for NEL yields, no difference was observed between both species. The best sowing date for canola is from September 25 on, with CP production advantages over oat.     

Evidence against associative N2 fixation as a significant N source in long-term wheat plots

In monocropped cereal systems, annual N inputs from non-fertilizer sources may be more than 30 kg ha^-1. We examined the possibility that these inputs are due to biological N₂ fixation (BNF) associated with roots or decomposing residues. Wheat was grown under greenhouse conditions in pots (34 cm long by 10 cm diameter) containing soil from a plot cropped to spring wheat since 1911 without fertilization. The roots and soil were sealed from the atmosphere and exposed to a¹⁵N₂-enriched atmosphere for three to four weeks during vegetative, reproductive or post-reproductive stages. This technique permitted detection of as little as 1 μg fixed N plant^-1 in plant material and 40 μg fixed N plant^-1 in soil. No fixation of¹⁵N₂ occurred during either of the first two labelling periods. In the final labelling period, straw returned to the soil was significantly enriched in¹⁵N, especially in a pot with a higher soil moisture content. Total BNF in this pot was 13 μg N plant^-1, or about 30 g N ha^-1. In a separate experiment with soil from the same plot, we detected BNF only when soil was amended with glucose at a high soil moisture content. Measured associative BNF was insufficient to account for observed N gains under field conditions. Lethbridge Research Centre contribution no. 3879488. Lethbridge Research Centre contribution no. 3879488.     

Studies on the efficacy of a phytohormone producing phosphate solubilizingBacillus firmus in augmenting paddy yield in acid soils of Nagaland

Summary A super strain ofBacillus firmus (NCIM-2636) producing a phytohormone, indole-3-acetic acid, in addition to its high ability to solubilize insoluble inorganic phosphates were applied in acid soils of Nagaland, India. Rice (Oryza sativa L.) variety Jaya and IR-8 were grown in kharif season in two successive years 1980 and 1981. After proper manuring the soils received single super phosphate (S.S.P.) and Mussoorie Rock phosphate (R.P.) separately at different doses. Yield of crop in both the years increased significantly due to bacterial inoculation. Maximum grain yield was recorded in Jaya variety under S.S.P. and R.P. when treatments were at the dose of 43.75 and 17.5 kg P ha⁻¹ respectively while the same in IR-8 variety under S.S.P. and R.P. treatments were at the dose of 35 and 17.5 kg P ha⁻¹ respectively. Maximum straw yield was produced by Jaya variety when 35 and 43.75 kg P ha⁻¹ in the form of S.S.P. and R.P. respectively were applied. Highest straw yield of IR-8 variety was obtained after the application of 17.5 kg P ha⁻¹ (S.S.P. and R.P.) in combination with phosphate solubilizing bacteria. Bacterial inoculation decreased the phosphorus availability in 1 st year but increased the same in 2nd year. Phosphorus content in grains was significantly enhanced in both the trials. Maximum uptake of phosphorus by grains was noted in Jaya variety at the dose of 47.5 kg P ha⁻¹ and in IR-8 variety at the dose of 52.5 kg P ha⁻¹ under S.S.P. treatment, while 8.75 and 35 kg P ha⁻¹ in the form of R.P. yielded similar results in Jaya and IR-8 varieties respectively. Phosphorus at the dose of 35 kg ha⁻¹ was found to cause more P-uptake by straw in both S.S.P. and R.P. treatments. The various data from the experiment conclusively proved that the bacterium in combination with R.P. produced the desired effect more prominently than when bacterium applied in combination with S.S.P.     

Physiological changes in soybean (Glycine max) Wuyin9 in response to N and P nutrition

Phosphorus deficiency is a very common problem in the acid soil of central China. Previous research has shown that starter N and N topdressing at the flowering stage (Rl) increased soybean (Glycine max) yield and N₂ fixation (Gan et al, 1997, 2000). However, there is little information available concerning soybean response to P‐fertiliser in soybean production in central China (Gan, 1999). A field experiment was conducted to investigate the response to P (0 kg P ha^?1, 22 kg P ha^?1, 44 kg P ha^?1 before sowing) and N fertiliser application (N1: 0 kg N ha^?1, N2: 25 kg N ha^?1 before sowing, N3: N2 + 50 kg N ha^?1 at the V2 stage and N4: N2 + 50 kg N ha^?1 at the R1 stage) on growth, yield and N₂ fixation of soybean. Both N and P fertiliser increased growth and seed yield of soybean (P < 0.01). Application of basal P fertiliser at 22 kg P ha^?1 or 44 kg P ha^?1 increased total N accumulation by 11% and 10% (P < 0.01) and seed yield by 12% and 13% (P < 0.01), respectively, compared to the zero P treatment. Although application of starter N at 25 kg N ha^?1 had no positive effect on seed yield at any P level (P > 0.05), an application of a topdressing of 50 kg N ha^?1 at the V2 or R1 stage increased total N accumulation by 11% and 14% (P < 0.01) and seed yield by 16% and 21% (P < 0.01), respectively, compared to the zero N treatment. Soybean plants were grown on sterilised Perlite in the greenhouse experiment to study the physiological response to different concentrations of phosphate (P1: 0 mM; P2: 0.05 mM; P3: 0.5 mM; P4:1.0 mN) and nitrate (N1: 0 mM with inoculation, N2: 20 mM with inoculation). The result confirmed that N and P nutrients both had positive effects on growth, nodulation and yield (P < 0.01). The relative importance of growth parameters that contributed to the larger biomass with N and P fertilisation was in decreasing order: (i) total leaf area, (ii) individual leaf area, (iii) shoot/root ratio, (iv) leaf area ratio and (v) specific leaf area. The yield increase at N and P supply was mainly associated with more seeds and a larger pod number per plant, which confirmed the result from the field experiment.     

NITROGEN FIXATION BY LEGUMES AND BLUE-GREEN ALGAL-LICHEN CRUSTS IN A COLORADO DESERT ENVIRONMENT

Potential sources of fixed nitrogen in a Colorado desert environment were examined by the acetylene reduction method at the Deep Canyon Desert Research Center, near Palm Desert, California. In field and greenhouse studies all members of the genera Astragalus, Dalea, Lotus, Lupinus, Melilotus, and Prosopis examined formed active nodules (acetylene reduction) with indigenous soil bacteria. No evidence of nodulation was found for Acacia greggii, Cercidium floridum, or Hoffmannseggia microphylla. Lotus tomentellus was estimated to fix 0.1 kg N ha⁻¹ by the time of flowering under field conditions. Several members of the genus Dalea showed substantial rates of acetylene reduction in the greenhouse: D. emoryi, 16.1 + 3.5, D. mollissima, 11.4 + 3.7, D. schottii 2.9 + 1.7, D. spinosa 2.5 + 0.4 μmoles ethylene plant⁻¹ hr⁻¹. In greenhouse assays where water was supplied continuously, blue-green algal-lichen crusts reduced acetylene at an average rate of 11.0 + 5.7 nmoles ethylene cm⁻² hr⁻¹ with a maximum of 57.1. But when in situ assays were done following irrigation of a field plot with 2.3 cm of water, much lower activities were observed with a maximum activity of only 6.4 nmoles cm⁻² hr⁻¹.     

N2 fixation in cowpea plants grown in farmers’ fields in the Upper West Region of Ghana, measured using15N natural abundance

Few studies have assessed the levels of symbiotic N nutrition in legumes grown by farmers in Africa. In this study, the shoots of cowpea plants were sampled from 63 farms in 12 villages within 5 districts of the Upper West Region of Ghana, and assessed for growth and symbiotic N nutrition. The data revealed considerable differences in cowpea plant density per m², plant growth,¹⁵N natural abundance (δ¹⁵N), %Ndfa, and N-fixed among different farms under one village, and between villages under the same district, and between districts in the Upper West Region. In farms where there were fewer cowpea plants per m², plant growth was better and dry matter yield per plant significantly greater, leading to strong variations in δ¹⁵N values. Except for four farms at Bamahu which had cowpea shoot Ndfa values of 12.1%, 30.0%, 36.5% and 46.6%, one farm at Babile with Ndfa value of 58.1%, and three farms at Silbelle with Ndfa values of 56.8%, 57.9% and 68.7%, the remaining 55 out of the 63 farms studied showed high shoot Ndfa values, ranging from 70.6% to 99.7%, which clearly indicates that cowpea cultivated by farmers in the Upper West Region of Ghana meet a large proportion of their N requirements from symbiotic fixation. At the district level, isotopic analysis showed that, on average, the¹⁵N natural abundance values (%0) of cowpea shoots were ?0.496±0.04 for Jirapa, ?0.083±0.06 for Nadowli, 0.368±0.08 for Lawra, J.333±0.29 for Wa and 0.365±0.09 for Sissala district. Estimates of the legume’s N derived from fixation were 66.3% for Wa district, 89.9% for Nadowli, 79.4% for Lawra, 78.9% for Sissala and 80.9% for Jirapa district. The amount of N-fixed ranged from 402.3 mg.plant^?1 for Nadowli, 176.5 mg.plant^?1 for Wa, 235.4 mg.plant^?1 for Sissala, 179.0 mg.plant^?1 for Lawra to 249.2 mg.plane^?1 for the Jirapa district. Expressed on per-hectare basis using cowpea density per m², the total amount of N-fixed was around 16.6 kg ha^?1 in the Nadowli district, 19.1 kg ha^?1 in Wa, 23.0 kg ha^?1 in Sissala, 2J.1 kg ha^?1 in Lawra and 17.6 kg ha^?1 in the Jirapa district. Averaged across all 5 districts, N-fixed by cowpea was about 19.5 kg ha^?1 in the Upper West Region of Ghana. These data suggest that, increasing N₂ fixation in fanners’ fields in Ghana would require optimization of cowpea plant density rather than biological manipulation of the symbiotic process (as %Ndfa values were generally very high).     

三种植物对土壤磷吸收和富集能力的比较北大核心CSCD

筛选磷富集植物是磷矿废弃地土壤与植被修复的关键。该文以向日葵(Helianthus annuus)、苏丹草(Sorghum sudanense)、南瓜(Cucurbita moschata)为研究对象,采用盆栽试验,设置5个磷浓度(0、100、300、500和700 mg·kg–1),分别在3个不同生长时段(4周、7周、10周)内采样,对这3种植物的磷吸收和富集能力进行了比较。结果表明:(1)在相同生长时间内,向日葵、苏丹草、南瓜的地上部磷含量均随磷处理浓度的升高而增大,最大值分别为9.67 g·kg–1、4.86 g·kg–1、6.32 g·kg–1;相同浓度下,向日葵地上部磷含量随着生长时间的延长呈上升趋势,苏丹草则呈下降趋势,南瓜无显著变化;(2)3种植物的地上部磷累积量均在磷处理浓度为700 mg·kg–1时,生长10周后达到最大值,分别为217.83 mg·plant–1、93.92 mg·plant–1、135.82 mg·plant–1;(3)各浓度处理下,向日葵、苏丹草的地上部磷富集系数和转移系数均大于1.00,南瓜的地上部磷富集系数和转移系数波动较大;向日葵的富集系数和转移系数最大值分别达11.39和4.09。综合比较可知,3种植物磷吸收和富集能力的大小顺序为:向日葵>南瓜>苏丹草。向日葵各项富磷特征基本符合磷富集植物的筛选标准,可作为磷矿废弃地土壤与植被修复的备选物种。     

Influence of Seeding Ratio,Planting Date,and Termination Date on Rye-Hairy Vetch Cover Crop Mixture Performance under Organic Management

Cover crop benefits include nitrogen accumulation and retention, weed suppression, organic matter maintenance, and reduced erosion. Organic farmers need region-specific information on winter cover crop performance to effectively integrate cover crops into their crop rotations. Our research objective was to compare cover crop seeding mixtures, planting dates, and termination dates on performance of rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth) monocultures and mixtures in the maritime Pacific Northwest USA. The study included four seed mixtures (100% hairy vetch, 25% rye-75% hairy vetch, 50% rye-50% hairy vetch, and 100% rye by seed weight), two planting dates, and two termination dates, using a split-split plot design with four replications over six years. Measurements included winter ground cover; stand composition; cover crop biomass, N concentration, and N uptake; and June soil NO₃ ^--N. Rye planted in mid-September and terminated in late April averaged 5.1 Mg ha^-1 biomass, whereas mixtures averaged 4.1 Mg ha^-1 and hairy vetch 2.3 Mg ha^-1. Delaying planting by 2.5 weeks reduced average winter ground cover by 65%, biomass by 50%, and cover crop N accumulation by 40%. Similar reductions in biomass and N accumulation occurred for late March termination, compared with late April termination. Mixtures had less annual biomass variability than rye. Mixtures accumulated 103 kg ha^-1 N and had mean C:N ratio <17:1 when planted in mid-September and terminated in late April. June soil NO₃ ^--N (0 to 30 cm depth) averaged 62 kg ha^-1 for rye, 97 kg ha^-1 for the mixtures, and 119 kg ha^-1 for hairy vetch. Weeds comprised less of the mixtures biomass (20% weeds by weight at termination) compared with the monocultures (29%). Cover crop mixtures provided a balance between biomass accumulation and N concentration, more consistent biomass over the six-year study, and were more effective at reducing winter weeds compared with monocultures.     

Litterfall from trees in semiarid woodlands of north‐east Queensland

The amount and chemical composition (nitrogen, phosphorus and sulfur concentrations) of the components of tree litter were measured in eucalypt woodlands at two sites (Cardigan and Hillgrove) near Charters Towers, Queensland, Australia. Annual litterfall averaged 720 kg ha^–1 (Cardigan) and 1270 kg ha^–1 (Hillgrove) over 3 years with leaves the major component at both sites. Rate of litterfall was greatest during September–December and lowest during May–July. Nutrient concentrations varied widely but no seasonal patterns were detected. Phosphorus concentrations in the leaf litter at Hillgrove (mean = 0.112%) were much higher than in other studies of eucalypt litter, probably reflecting the high soil phosphorus levels at the study site. Tree litter represents an important proportion of the organic material and nutrients being cycled through these woodlands.     

Biomass production by irrigated and fertilized Salix clones

In an attempt to assess maximum biomass production of willows, field experiments with irrigation and fertilization (through the same system) were carried out in the south of Sweden (57°N). The site was near the coast on a sandy soil (pH 5) on which the populations of herbivores (moose and voles) were small. Different irrigation systems were tested on a 1-ha experimental area: drip-, sprinkler, and a subsurface system. Fertilization was carried out from the last week of May until early September. A liquid fertilizer, complete except for calcium and magnesium, was given in an amount corresponding to an addition of 10 kg. ha⁻¹. week⁻¹, with the other nutrients in optimum proportions. Irrigation started during the first week of May 1985, and continued twice a week throughout the month with 30 mm on each occasion. The rest of the growing season was very wet, and consequently irrigation was limited to 10 mm a week in June, July, and August. The total amount of irrigation given to the crop during the growing season was 330 mm and precipitation was 271 mm. The crop was fertilized with 150 kg. ha⁻¹ of nitrogen with other nutrients in optimal proportions. Leaves were analysed for macronutrients and the ground-water for nitrate and ammonium.The above-ground production of woody biomass for a Salix dasyclados Vimm. clone during its third year on 4-year-old roots was 3·6 kg. m⁻² dry matter for a drip irrigated plot. The comparable result for the subsurface system was 2·8 kg. Two-year-old shoots on 4-year-old roots of the same clone for a drip system plot produced 3·0 kg m⁻². Production of 1 kg. m⁻² corresponds to 10 tonne or 25 m³. ha⁻¹. Annual production in clones of Salix viminalis L. was only 1·2–1·8 kg.m⁻² during the second and third years. Tests using N¹⁵-labelled fertilizer have so far shown no leakage in the groundwater. The capacity of some of the Salix clones to convert solar energy into biomass is higher than for any other crop in Sweden, whether in forestry or agriculture.     

Nitrogen fertilization to optimize the greenhouse gas balance of hemp crops grown for biomass

Nitrogen trials were carried out on hemp crops grown in Ireland over a 3 year period to identify nitrogen fertilization strategies which optimize the greenhouse gas (GHG) and energy balances of hemp crops grown for biomass. Nitrogen rates up to 150 kg N ha^?1 were used in the study. Yield increased with nitrogen rate up to 120 kg N ha^?1 for early (Ferimon), mid (Felina 32) and late maturing (Futura 75) varieties. Variety had a significant effect on yield with yields increasing with maturation date. In 2 years of the study, certain application rates of nitrogen were applied either at sowing, at emergence, after emergence or split between these dates to determine if nitrogen rates could be reduced by delaying or splitting the applications. The application of nitrogen at times later than sowing or in splits during the early part of the growing season had no significant effect on biomass yield compared with the practice of applying nitrogen at the time of sowing. Late applications of nitrogen reduced leaf chlorophyll content and height early in the growing season. Later in the growing season, there was no difference in height between treatments although the highest concentrations of chlorophyll were found in the leaves of the late application treatment. Nitrogen rate and the timing of nitrogen application had no effect on plant density. Biomass yield, net energy and net GHG mitigation increased up to an application rate of 120 kg N ha^?1, this result was independent of soil type or soil nitrogen level. Net GHG and energy balance of hemp crops grown for biomass are optimized if late maturing varieties are used for biomass production and a nitrogen rate of 120 kg ha^?1 is applied at sowing.     

Effect of nitrogen and chlormequat chloride on the seed yield and oil content of mustard (Brassica juncea L. Czern & Coss)

The growth of mustard was increased significantly when treated with up to 80 kg N ha^–1 (N₈₀). Spraying with (2-chloroethyl) trimethylammoniumchloride (chlormequat chloride) increased seed yield and seed protein content. Spraying nitrogen fertilized plots with chlormequat chloride, increased leaf area, leaf area ratio, leaf area duration, number of siliquae plant^–1, number of seeds siliqua^–1 and length of siliqua. Reducing, non-reducing and total sugars in the leaves at 80 days after sowing were also affected significantly. Chlorophyll a, b and total chlorophyll were little affected. The number of siliquae plant^–1 was highly correlated with seed yield in both the seasons of experimentation. The correlation coefficient value () was 0.586 in 1982/83 and 0.912 in 1983/84.The total accumulation of nutrients, i.e. nitrogen, phosphorus and potassium in seed and straw was significantly affected by N₈₀ × chlormequat chloride interaction.     

Data-driven estimation of nitric oxide emissions from global soils based on dominant vegetation covers

Soils are a major source of global nitric oxide (NO) emissions. However, estimates of soil NO emissions have large uncertainties due to limited observations and multifactorial impacts. Here, we mapped global soil NO emissions, integrating 1356 in-situ NO observations from globally distributed sites with high-resolution climate, soil, and management practice data. We then calculated global and national total NO budgets and revealed the contributions of cropland, grassland, and forest to global soil NO emissions at the national level. The results showed that soil NO emissions were explained mainly by N input, water input and soil pH. Total above-soil NO emissions of the three vegetation cover types were 9.4 Tg N year⁻¹ in 2014, including 5.9 Tg N year⁻¹ (1.04, 95% confidence interval [95% CI]: 0.09–1.99 kg N ha⁻¹ year⁻¹) emitted from forest, 1.7 Tg N year⁻¹ (0.68, 95% CI: 0.10–1.26 kg N ha⁻¹ year⁻¹) from grassland, and 1.8 Tg N year⁻¹ (0.98, 95% CI: 0.42–1.53 kg N ha⁻¹ year⁻¹) from cropland. Soil NO emissions in approximately 57% of 213 countries surveyed were dominated by forests. Our results provide updated inventories of global and national soil NO emissions based on robust data-driven models. These estimates are critical to guiding the mitigation of soil NO emissions and can be used in combination with biogeochemical models.     

Impact of sheep grazing on nutrient budgets of dry heathlands

Questions: What effect does sheep grazing have on the nutrient budgets of heathlands? Can grazing compensate for atmospheric nutrient loads in heathland ecosystems? What are the conclusions for heathland management? Location: Lüneburg Heath, NW Germany. Methods: During a one-year grazing experiment (stocking rate 1.1 sheep/ha) nutrient balances for N, Ca, K, Mg and P were calculated by quantifying input rates (atmospheric deposition, sheep excrement) and output rates (biomass removal, leaching). Results: Atmospheric nutrient deposition amounted to 22.8 kg.ha⁻¹.a⁻¹ for N and < 0.2 kg.ha⁻¹.a⁻¹ for P. Sheep excrement increased the inputs for N and P by ca. 3.5 and 0.2 kg.ha⁻¹.a⁻¹, respectively. Grazing reduced N- and P-stores in the above-ground biomass by 25.6 and 1.9 kg.ha⁻¹.a⁻¹, respectively. N-and P-losses via leaching amounted to 2.2 and < 0.2 kg.ha⁻¹.a⁻¹. Output:input ratios for P were high, indicating that grazing severely affected P-budgets of heaths. Conclusions: Our results suggest that sheep grazing has the potential to compensate for atmospheric nutrient loads (particularly for current N deposition rates). However, in the long term the combination of elevated N-deposition and P-loss due to grazing may cause a shift from N-(co-) limited to more P-(co-) limited plant growth. To counteract an aggravation of P-deficiency in the long term, grazing may be combined with management measures that affect P-budgets to a lesser extent (e.g. prescribed burning).     

Soil amendment with biochar and manure alters wood stake decomposition and fungal community composition

Biochar and manure can be used for sustainable land management. However, little is known about how soil amendments might affect surface and belowground microbial processes and subsequent wood decomposition. In a split-split-split plot design, we amended soil with two rates of manure (whole plot; 0 and 9 Mg ha⁻¹) and biochar (split plot; 0 and 10 Mg ha⁻¹). Wood stakes of three species (hybrid poplar, triploid Populus tomentosa Carr.; aspen, Populus tremuloides Michx.; and pine, Pinus taeda L.) were placed in two positions (horizontally on the soil surface, and inserted vertically in the mineral soil), which served as a substrate for fungal growth. In 3 years, the decomposition rate (density loss), moisture content, and fungal community (via high-throughput sequencing methods) of stakes were evaluated. Results indicated that biochar and/or manure increased the wood stake decomposition rates, moisture content, and operational taxonomic unit abundance. However, the richness and diversity of fungi were dependent on wood stake position (surface > mineral), species (pine > the two Populus), and sample dates. This study highlights that soil amendment with biochar and/or manure can alter the fungal community, which in turn can enhance an important soil process (i.e., decomposition).     

Phosphorus cycling in a small watershed in the Brazilian Cerrado: impacts of frequent burning

Plant productivity in many tropical savannas is phosphorus limited. The biogeochemical cycling of P in these ecosystems, however, has not been well quantified. In the present study, we characterized P stocks and fluxes in a well-preserved small watershed in the Brazilian Cerrado. As the Cerrado is also a fire-dominated ecosystem, we measured the P stocks and fluxes in a cerrado stricto sensu plot with complete exclusion of fire for 26 years (unburned plot) and then tested some predictions about the impacts of fire impacts on P cycling in an experimental plot that was burned three times since 1992 (burned plot). The unburned area is an ecosystem with large soil stocks of total P (1,151 kg ha^?1 up to 50 cm depth), but the largest fraction is in an occluded form. Readily extractable P was found up to 3 m soil depth suggesting that deep soil is more important to the P cycle than has been recognized. The P stock in belowground biomass (0?C800 cm) was 9.9 kg ha^?1. Decomposition of fine litter released 0.97 kg P ha^?1 year^?1. Fluxes of P through bulk atmospheric deposition, throughfall and litter leachate were very low (0.008, 0.006 and 0.028 kg ha^?1 year^?1, respectively) as was stream export (0.001 kg ha^?1 year^?1). Immobilization of P by microbes during the rainy season seems to be an important mechanism of P conservation in this ecosystem. Fire significantly increased P flux in litter leachate to 0.11 kg ha^?1 year^?1, and added 1.2 kg ha^?1 of P in ash deposition after fire. We found an increase of P concentration in soil solution at 100 cm depth (from 0.03 ??g l^?1 in unburned plot to 0.3 ??g l^?1 in the burned plot). In surface soils (0?C10 cm) of the burned plot, fire decreased the concentrations of extractable organic-P fractions, but did not significantly increase inorganic-P fractions. The reduction of extractable soil organic P in the burned plot in topsoil and the increase of P in the soil solution at greater depths indicated a reduction of P availability and may increase P fixation in deep soils. Repeated fire events over the long term may result in significant net loss of available forms of phosphorus from this ecosystem.