Biomass production and N fixation of five Mucuna pruriens varieties and their effect on maize yields in the forest zone of Cameroon

Mucuna has been tested intensively in past years as green manure for intensive maize production in West Africa. However, information is missing about the yield effect of different existing mucuna varieties. Five Mucuna pruriens varieties were grown for 40 weeks followed by sole maize (Zea mays L.) in order to determine differences in biomass production, nitrogen fixation, and effects on maize yield. Mucuna varieties differed in length of growing period, total biomass production (5.9—8.8 Mg ha^—1), seed production (0.65—1.3 Mg ha^—1), nitrogen (N) uptake (147—222 kg ha^—1), N fixation (87—171 kg ha^—1), and the amount of N retained in residues (138—218 kg ha^—1). The grain yield of maize grown immediately after the short mucuna fallow was significantly higher after mucuna vars. jaspaeda (4.60 Mg ha^—1), utilis (3.49 Mg ha^—1), and cochinchinensis (3.44 Mg ha^—1), compared with a non‐fertilized control (1.93 Mg ha^—1) which had a maize crop and vegetation regrowth before. After mucuna vars. ghana and veracruz, 2.90 and 2.65 Mg ha^—1 of maize grain were produced, respectively. No significant correlation between mucuna biomass and its N uptake and maize grain yield was found, whereas maize stover yield showed a significant positive correlation. Application of 30, 60, and 90 kg ha^—1 N as <?tw=98%>urea on sub‐plots of the control yielded 2.20, 3.19, and 3.46 Mg ha^—1 <?tw>of maize grain in the first year. Only the difference between 0 and 90 kg ha^—1 N was significant. Fertilizer N equivalent values for mucuna varieties ranged from 41 to 148 kg ha^—1. The yield advantage of vars. jaspaeda, utilis, and cochinchinensis versus the control without N fertilizer application was confirmed in the following year, with no significant difference in maize grain yield between mucuna and the control with N fertilizer application.<?show $6#>     

Nitrogen Fixation,Soil Nitrogen Availability,and Biomass in Pure and Mixed Plantations of Alder and Pine in Central Korea

ABSTRACT

Rates of nitrogen (N) fixation, soil N availability, and aboveground biomass were measured in 27-year-old pure and mixed Alnus hirsuta and Pinus koraiensis plantations in central Korea. Nodule biomass and N fixation were 179.3 kg ha^{? 1} and 46.6 kg ha^{? 1}yr^{? 1} for the pure A. hirsuta plantation (PA) and 95.2 kg ha^{? 1} and 41.1 kg ha^{? 1}yr^{? 1} for the mixed A. hirsuta + P. koraiensis plantation (MAP), respectively. A. hirsuta seemed to provide more than two thirds of annual N requirement for P. koraiensis.Rates of acetylene reduction were significantly related to soil temperature (R² = 0.51, P < 0.001), but not to soil moisture content. Total inorganic N [ammonium (NH₄ ⁺)plus nitrate (NO₃ ^?)] availability measured using ion exchange bags were significantly higher under PA (27.91 μ g-N bag^{? 1}) and MAP (31.34 μ g-N bag^{? 1}) than under the pure P. koraiensis plantation (PP) (14.31 μ g-N bag^{? 1}). Especially soils under the influence of A. hirsuta showed at least 2 fold increase in resin total inorganic N concentrations. Total aboveground biomass (Mg ha^{? 1}) was 147.3 for PA, 145.8 for MAP, and 174.8 for PP, respectively, and was not significantly different among plantations. A. hirsuta significantly increased soil N availability; however, the influence of N fixation on aboveground biomass was not significant for the study plantations.     

Long‐term effects of fertilization on some soil properties under rainfed soybean‐wheat cropping in the Indian Himalayas

This study aims to examine the effects of long‐term fertilization and cropping on some chemical and microbiological properties of the soil in a 32 y old long‐term fertility experiment at Almora (Himalayan region, India) under rainfed soybean‐wheat rotation. Continuous annual application of recommended doses of chemical fertilizer and 10 Mg ha^–1 FYM on fresh‐weight basis (NPK + FYM) to soybean (Glycine max L.) sustained not only higher productivity of soybean and residual wheat (Triticum aestivum L.) crop, but also resulted in build‐up of total soil organic C (SOC), total soil N, P, and K. Concentration of SOC increased by 40% and 70% in the NPK + FYM–treated plots as compared to NPK (43.1 Mg C ha^–1) and unfertilized control plots (35.5 Mg C ha^–1), respectively. Average annual contribution of C input from soybean was 29% and that from wheat was 24% of the harvestable aboveground biomass yield. Annual gross C input and annual rate of total SOC enrichment from initial soil in the 0–15 cm layer were 4362 and 333 kg C ha^–1, respectively, for the plots under NPK + FYM. It was observed that the soils under the unfertilized control, NK and N + FYM treatments, suffered a net annual loss of 5.1, 5.2, and 15.8 kg P ha^–1, respectively, whereas the soils under NP, NPK, and NPK + FYM had net annual gains of 25.3, 18.8, and 16.4 kg P ha^–1, respectively. There was net negative K balance in all the treatments ranging from 6.9 kg ha^–1 y^–1 in NK to 82.4 kg ha^–1 y^–1 in N + FYM–treated plots. The application of NPK + FYM also recorded the highest levels of soil microbial‐biomass C, soil microbial‐biomass N, populations of viable and culturable soil microbes.     

Sweet Sorghum [Sorghum bicolor (L.) Moench] Biomass Production for Biofuel and the Effects of Soil Types and Nitrogen Fertilization

This research aimed to determine the optimum nitrogen fertilization rate on three soils for producing biomass sweet sorghum (Sorghum bicolor cultivar M81E) and corn (Zea mays cultivar P33N58) grain yield and to compare their responses. The research was conducted in Missouri in rotations with soybean, cotton, and corn. Seven rates of nitrogen (N) were applied. Sweet sorghum dry biomass varied between 11 and 27.5 Mg ha^?1) depending on year, soil type, and N rate. Nitrogen fertilization on the silt and sandy loam soils had no effect (P > 0.05) on sweet sorghum yield grown after cotton and soybean. However, yield increased in the clay soil. Corn grain yielded from 1.3 to 12.9 Mg ha^?1, and 179 to 224 kg N ha^?1 was required for maximum yield. Increasing biomass yield required N application on clay but not on silt loam and sandy loam in rotations with soybean or cotton.     

Wachstum und Ernährung von Eberesche,Buche und Fichte im Gefäßversuch mit immissionsbelasteten Bodensubstraten aus dem Erzgebirge

Influence of simulated sulphur and nitrogen depositions on biomass and nutrient relationships of mountain ash, European beech and Norway spruce in a pot experiment with two soil substrates from the Ore Mountains Growth and nutrient relationships of mountain ash (Sorbus aucuparia), European beech (Fagus sylvatica) and Norway spruce (Picea abies) were investigated in a pot experiment with the two substrates rhyolithe (acidic) and basalt (alkaline). Additionally, depositions of sulphur (S) and nitrogen (N) as expected to occur in the Ore Mountains (Saxonia, Germany) in the future were simulated in order to test the species′ suitability for forest regeneration. After two years, aboveground biomass was significantly higher on basalt compared to rhyolithe for all species. The amount of S given (0 and 100 kg ha^—1 a^—1) and the dominant form of N applied (NH₄⁺:NO₃^— = 1:4 and 4:1; total amount of N given 80 kg ha^—1 a^—1) were of minor influence only. The contents of N and K in leaves or needles were higher on rhyolithe, whereas P, Ca, Mg and Mn contents were higher on basalt. Nutrient contents were only slightly affected by the amount of S supply and the NH₄⁺:NO₃^— ratio. In contrast to mountain ash, beech saplings exhibited considerable growth on rhyolite. It is therefore concluded that beech may be a suitable species for forest regeneration even on acidic soils suffering heavily from S and N immissions, whereas spruce will not tolerate high S loads. However, increasing N depositions by stimulating growth may cause deficiencies of Mg and K in both species.     

Coniferous afforestation increases soil carbon in maritime sand dunes

Afforestation of grasslands can increase C sequestration and provide additional economic and environmental benefits. Pine plantations, however, have often been found to deplete soil organic C and trigger detrimental effects on soils. We examined soil characteristics under a 45-year-old Pinus radiata stand and under adjacent grassland on maritime dunes in temperate Argentina. Soil under the pine plantation had greater soil organic C (+93%), total N (+55%) and available P (+100%) concentrations than under grassland. Carbon was stored under the pinestand at an estimated mean accretion rate of 0.64 Mg ha^?1 y^?1. At 0- to 25-cm depth, soil C amounted to 61 Mg ha^?1 under pine and 27 Mg ha^?1 under grassland. Soil C accumulated more on dune slopes (35 Mg ha^?1 y^?1) than on ridges(29 Mg ha^?1 y^?1) and bottoms (12 Mg ha^?1 y^?1). Compared with the grassland, soil acidity, cation-exchange capacity, base losses (K > Ca = Mg) and C/N ratio increased under pine. Spatial heterogeneity in soil characteristics was greater under pine than under grassland. Such variability was non-systematic and did not support the ‘single-tree influence circle’ concept. Afforestation increased C in soil, forest floor and tree biomass in dunes with ustic climate regime.     

Use of nitrogen‐15 microplots for field studies of maize nitrogen‐use efficiency

Abstract

Choice of minimum size of nitrogen (¹⁵N) microplots is essential in studies of maize (Zea mays L.) N uptake, translocation, assimilation, and accumulation patterns using the ¹⁵N isotopic technique. The objectives of this field experiment were to determine if: i) plants adjacent to restricted ¹⁵N microplots (0.76 m × 0.23 m × 0.25 m deep, centred on a plant) were ¹⁵N‐enriched, ii) growth of plants in microplots was hampered, and iii) the estimated fertilizer N recovery (FNR) was lower than that previously reported. There was no detectable enrichment by applied ¹⁵N in maize plants adjacent to the microplots. Root and aboveground biomass and N content of plants in the microplots were similar to plants in the main plot at harvest (P>0.1). The FNR in the aboveground plants was 29% for 200 kg N ha^‐1 and 38% for 100 kg N ha^‐1 treatment with 18 and 26% in the corresponding grains. These values were similar to those reported in the literature where larger non‐restricted or restricted microplots were used. Our data suggest that single‐plant microplots are appropriate for ¹⁵N tracer studies on maize and provide good estimates of N utilization.     

Influence of Quercus ilex trees on herbaceous production and nutrient concentrations in southern PortugalElena Cubera1, 2

In an open woodland in Portugal, the nature of interactions between Quercus ilex trees and herbaceous plants was assessed during 2 years by studying how manipulation of incident solar radiation, water and nutrient supply affect the herbaceous biomass and N, K, P, Ca, Mg, and Mn concentrations. Measurements were carried out in three environments consisting of (1) open grassland, (2) beneath the tree canopy, and (3) under artificial shade. Each of these environments was subjected to two regimes of fertilization and two water levels in a factorial design. The fertilizer treatment consisted of application of no fertilizer or a combination of 200 kg calcium ammonium nitrate ha^–1 (26% N) and 350 kg superphosphate ha^–1 (8% P), while the water‐supply treatment consisted of either no irrigation or irrigation fortnightly from February 1 to April 30. Grasses showed significantly lower nutrient concentrations than forbs. However, nutrient concentrations of the whole herbaceous community were within the recommended ranges for cattle nutrition. A negative effect of shade on herbaceous biomass production was observed. The effect of watering on herbaceous biomass was less prominent than the effect of fertilization, irrespective of the environment, suggesting that Q. ilex does not compete for soil‐water resources with herbaceous biomass in this ecosystem. Fertilization increased total biomass by 106%, 49%, and 97% in the open grassland, beneath the tree canopy, and under artificial shade, respectively. During the first and second year, fertilization increased herbaceous P concentrations by 24% and 83%, respectively, if compared with concentrations obtained at the unfertilized plots. Higher K and Mg concentrations were observed in herbaceous plants beneath the tree canopy than in the open areas, indicating a positive effect of trees on pasture quality. The positive and negative effects of trees on understory forage are discussed.     

华北平原夏玉米临界氮稀释曲线的验证

The concept of critical N concentration （Nc） has been widely used in agronomy as the basis for diagnosis of crop N status, and allows discrimination between field situations of sub-optimal and supra-optimal N supply. A critical N dilution curve of Nc= 34.0W-0.37, where W is the aboveground biomass （Mg DM ha-1） and Nc the critical N concentration in aboveground dry matter （g kg-1 DM）, was developed for spring maize in Europe. Our objectives were to validate whether this European critical N dilution curve was appropriate for summer maize production in the North China Plain （NCP） and to develop a critical N dilution curve especially for summer maize production in this region. In total 231 data points from 16 experiments were used to test the European critical N dilution curve. These observations showed that the European critical N dilution curve was unsuitable for summer maize in the NCP, especially at the early growth stage. From the data obtained, a critical N dilution curve for summer maize in the NCP was described by the equation of Nc = 27.2W-0.27, when aboveground biomass was between 0.64 and 11.17 Mg DM ha-1. Based on this curve, more than 90% of the data for the N deficiency supply treatments had an N nutrition index （NNI） 〈 1 and 92% of the data for the N excess supply treatments had an NNI 〉 1.     

Structure and biomass of larch stands regenerating naturally after clearcut logging

Variations in the succession following cutting of a herbaceousLarix sibirica Ledeb. phytocoenosis along the southern boundary of boreal forests in southern Siberia and in Eastern Hentey, Mongolia, were studied. Morphometric methods were used to determine the dimensional hierarchies of coenopopulation individuals. Structure and productivity of the aboveground components including standing wood, herbaceous cover and litter were studied. The maximum aboveground phytomass was measured as 212.3 Mg ha^?1 (oven dry mass). The highest total aboveground biomass productivity rate of aLarix sibirica phytocoenosis located at its southern limit exceeds 7 Mg ha^?1 per year. The maximum annual phytomass increment was found to be 4.4 Mg ha^?1 for the overstorey trees, 2.1 Mg ha^?1, for the herbaceous layer and 0.7 Mg ha^?1 for forest litter.     

NITROGEN ACCUMULATION IN SHOOTS AS A FUNCTION OF GROWTH STAGE OF CORN AND WINTER WHEAT

Midseason fertilizer nitrogen (N) rates based on predicted yields can be projected if the quantity of N accumulated in winter wheat (Triticum aestivum L.) and corn (Zea mays L.) is known especially early in the growing season. This study was conducted in 2006 and 2007 to establish the amount of N accumulated in corn and winter wheat over the entire growing season. Plots representing three N fertilization rates 0, 45, and 90 kg ha^?1 at Stillwater and 0, 67, and 112 kg ha^?1 at Lahoma were selected from two long-term wheat experiments located at research stations in Stillwater and Lahoma, Oklahoma. For corn, three N fertilization rates 0, 112 and 224 kg ha^?1 at Lake Carl Blackwell and 0, 56 and 112 kg ha^?1 at Perkins were selected from N studies, located at research stations near Lake Carl Blackwell and Perkins, Oklahoma. Sequential aboveground biomass samples were collected from 1 m² area of wheat and 1.5 m long row (0.76 cm spacing) for corn throughout their respective growing seasons. In general, this work showed that more than 45% of the maximum total N accumulated could be found in corn plants by growth stage V8 (8th leaf collar fully unfolded). For winter wheat, more than 61% of the maximum total N accumulated at later stages of growth could be accounted for by Feekes growth stage 5 (F5, leaf strongly erected). Our findings are consistent with those of others showing that yield potential can be predicted at mid-season since such a large percentage of the total N accumulated was accounted for early on in the growing cycle of either wheat or corn.     

塔河流域天然胡杨林不同林龄地上生物量及碳储量

[目的]探讨不同林龄单株胡杨地上部分生物量、林分的生物量及碳储量的分布特征,为进一步开展胡杨天然林生态系统碳循环、碳储量、固碳速率和潜力研究提供基础。[方法]以新疆维吾尔自治区轮台县天然胡杨林为研究对象,利用不同林龄下不同径阶的标准解析木样本数据,构建胡杨地上部分各器官的生物量回归模型,探讨不同林龄胡杨地上部分的生物量组成、分配以及各器官生物量随年龄的变化规律。[结果]随着林龄的增加,单株胡杨地上部分各器官生物量呈上升趋势,其中树干占主导地位。幼龄林、中龄林、近熟林、成熟林、过熟林的林分地上生物量分别为:4.91,7.95,19.47,61.95,47.64t/hm2,且随林龄的增加胡杨林地上部分生物量先增加后稍有降低;胡杨林地上部分不同器官平均含碳率从大到小依次为:树干(48.17%)树枝(47.75%)树皮(46.13%)树叶(44.90%),且随林龄的增加不同器官含碳率先增加后降低,但各器官之间含碳率差异不显著;塔河流域胡杨林碳储量随林龄先增加后降低,大小顺序为成熟林(30.38t/hm2)过熟林(23.26t/hm2)近熟林(9.30t/hm2)中龄林(3.69t/hm2)幼龄林(2.20t/hm2)。[结论]地上部分各器官碳储量按依次排列为:树干树枝树皮树叶,树干是胡杨林地上部分碳储量的主要器官。     

Effect of burning on soil organic matter content and N mineralization under shifting cultivation system of Karen people in Northern Thailand

In the traditional shifting cultivation system practiced by the Karen people in northern Thailand, the effects of burning on the content of extractable organic matter, microbial biomass, and N mineralization process of the soils were studied. Five plots (5×5 m² quadrat) with 0, 10, 20, 50, and 100 Mg ha^-1 of slashed materials were arranged and burned. Ten to 20 Mg ha^-1 of slashed biomass corresponded to the amount commonly burned by the Karen people. During the burning process, the soil temperature at the depth of 2.5 cm in the 100 Mg ha^-1 plot almost evenly increased to 300°C while the temperature in the 10 to 50 Mg ha^-1 plots increased with large variations from 50 to 300°C. Burning caused a conspicuous increase in the contents of organic C and (organic + mineral)-N extracted at room temperature and a simultaneous decrease in the contents of microbial biomass C and N, especially in the soil of the 100 Mg ha^-1 plot. In the rainy season, the values of the changes induced by burning reverted to the values recorded before burning, except for the microbial biomass in the 100 Mg ha^-1 plot, which still remained lower. Based on an incubation experiment, N mineralization rate was higher in the soils taken just after burning, especially in the 100 Mg ha^-1 plot, than in the soils taken during the rainy season. However, the soil in the 100 Mg ha^-1 plot was considered to have the lowest ability to supply mineral N among the soils in the rainy season. Burning of 10 to 20 Mg ha^-1 biomass corresponding to the values recorded in Karen peoples' shifting cultivation system was more compatible with soil ecology in terms of N supply at the initial stage of crop growth and of microbial biomass recovery during the rainy season, compared to the burning of 100 Mg ha^-1 biomass corresponding to the value recorded in a natural forest. Thus, the shifting cultivation system implemented by the Karen people can be considered to be a well-balanced agricultural system.     

Do Cover Crop And Soil-Mediated Legacy Influence Succeeding Wheat Production?

ABSTRACT

Biotic interaction of cover crops (CCs) can have a legacy effect on succeeding crops mediated by changes in nutrient dynamics. Depending on species, CCs influence nitrogen (N) dynamics by sequestering N and subsequent N release. Interactions of three CC species, Austrian Pea (Pisum sativum L.), winter rye (Secale cereal L.), and winter camelina (Camelina sativa L.), and three different soils were studied under greenhouse conditions on wheat (Triticum aestivum L.) grain yield and soil N availability. CCs were grown for two months and then incorporated, followed by the planting of wheat. CC biomass production ranged from 0.10 to 2.05 Mg ha^?1 in this order by species: Pea> Rye> Camelina. Biomass production by soil was in the order of Casselton>Ada>Minot. Succeeding wheat grain yield and grain N uptake was highest under pea in the order of pea>camelina>control>rye. Rye reduced grain yield and N uptake. Wheat yield ranged from 2.19 to 3.24 Mg ha^?1 depending on CC species-soil interaction. The N balance showed a 3–79% higher N surplus with the CCs. The N balance ranged from 78 kg N ha^?1 for the control to 140 kg N ha^?1 for pea. N surplus was greater for a pea in all soils, indicating pea can be regarded as an effective cover that can efficiently recycle N and provide additional agronomic benefits. Greater N balance with CCs shows that CCs can increase the amount of N accounted for in the system, which can significantly affect the N dynamics throughout the growing season.     

Differentiating between the supply of N to wheat from above and belowground residues of preceding crops of pea and canola

Belowground N comprises an important component of total residue N, but the N from this pool is often not included in studies that use ¹⁵N approaches to trace residue-derived N in succeeding crops. The objective of this greenhouse study was to differentiate between N supplied from aboveground and belowground crop residues, including rhizodeposits, of pea and canola to wheat using ¹⁵N labeling. A cross ¹⁵N-labeling approach was used in which wheat was grown on ¹⁵N-labeled belowground residues and non-labeled aboveground residues and vice versa. On average, the amount of N in wheat derived from belowground residues was almost twice the amount from aboveground residues. The higher input of both aboveground and belowground residue biomass and hence residue N from canola compared to pea tended to increase the residue-derived N in wheat from canola (6.4 %) relative to pea (4.7 %). However, differences in the percent recovery of ¹⁵N based on the amount of residue-¹⁵N initially applied revealed that a higher proportion of belowground residue N from pea (13.4 %) was recovered in wheat compared to the corresponding aboveground residue N from pea (8.8 %), and both belowground and aboveground residue N from canola (6.5 and 7.3 %, respectively). The total supply of N to wheat from preceding pea and canola crops was relatively low, likely due to wide C/N ratios. This study demonstrates the importance of belowground residue N to the supply of N to succeeding crops as well as differences between species.     

Use of blue-green algae and bryophyte biomass as a source of nitrogen for oil-seed rape

Summary Blue-green algal (Nostoc muscorum) or bryophyte (Barbula recurvirostra) growth on the surface of a brown earth silt loam contained in flooded columns significantly increased soil C (+20.9% and ±23.0%, respectively) and soil N (+25.1% and +9.6%, respectively) after 5 weeks in the surface 0.7-cm soil layer. Differences in the lower layers were not significant since there was no movement of C or N metabolites down the profile, even after 21 weeks. The input of C by the inoculated blue-green algae was estimated at 0.48 Mg C 100^-1 g soil or 0.45g C ha^-1; the bryophyte growth gave 0.5 Mg C ha^-1. N fixation by the blue-green algae alone was estimated at 60 kg N ha^-1 after 5 weeks of growth. Blue-green algae associated with bryophyte growth had fixed 23 kg N ha^-1 after 5 weeks, rising to 40 kg ha^-1 after 21 weeks. Decomposition of the bryophyte biomass led to a significant increase in the dry weight (+16.8%) and the N uptake (+27.5%) of spring oil-seed rape planted in homogenised soil. In contrast, soil incorporation of the blue-green algal biomass had no significant effect on yield. The equivalent mineralized N from the blue-green algal and bryophyte incorporation was estimated as 24 and 58 kg N ha^-1, respectively.     

Annual Burning Enhances Biomass Production and Nutrient Cycling in Degraded Imperata Grasslands

The invasive species Imperata cylindrica is a dominant grass covering a large part of degraded lands of India. Imperata is managed through traditional annual burning, a practice that is prevalent throughout tropical grasslands. A field experiment was conducted to quantify the effects of burning on aboveground and belowground biomass production and soil organic carbon (SOC), total nitrogen (TN), available phosphorus (Ave P), potassium (K⁺), calcium (Ca⁺), and magnesium (Mg⁺) concentrations in 0‐ to 15‐cm soil depth under Imperata grassland. The burnt site had 44% and 14% higher aboveground and belowground biomass over the un‐burnt control plots after 300 days of the fire event. The concentrations of SOC, TN, and Ave P increased soon after the fire but decreased regressively with time after the fire in both micro and macro soil aggregate size fractions. In contrast, concentrations of K⁺, Ca⁺, and Mg⁺ increased up to 30 days after the fire in both soil aggregate fractions. Burning did not significantly alter the stoichiometric ratios (C : N, C : P, and N : P) in macro aggregates. However, burning significantly reduced the C : N, C : P, and N : P ratios in micro aggregates during the first 0–30 days. Fire increased nutrient stocks (kg ha⁻¹) by 20–35% in the burnt site in comparison to an un‐burnt control site. It is concluded that the conventional practice of annual burning increases soil nutrients in surface soils and supports higher biomass production in Imperata‐covered degraded lands. Copyright © 2017 John Wiley & Sons, Ltd.     

Assessing resource use in gerbera genotypes for precision nutrient use in protected condition

Abstract

The present study was conducted in the existing germplasm block of gerbera under protected condition at ICAR-IIHR, Bengaluru, India during 2017–2019 to obtain comprehensive information on biomass partitioning, nutrient uptake pattern and flower yields in different genotypes for precision use of critical inputs. The number of leaves (187.6–353.2 m^?2?yr^?1) and flower stalks (166.9–274.5 m^?2?yr^?1) varied significantly among genotypes. Specific leaf area (SLA) was similar among Balance, Stanza, Arka Aswha and Terra Kalina cultivars (0.150–0.156?cm² mg^?1). Strong positive influence of SLA on number of flower stalks was evident from the significant correlation (r = –0.774). Significant positive correlations among number of flower stalks and leaves, leaf area and SLA substantiate the flower yield pattern in gerbera. Optimum leaf number per plant was estimated at 18.6, while optimum range was quantified at 14.1 to 22.4. In gerbera genotypes, the partitioning of total aboveground dry biomass to leaves and flower stalks was 46–61% and 39–54%, respectively. The average nutrient removal was quantified at 32.8?g N, 7.3?g P, 78.7?g K, 24.7?g Ca and 4.1?g Mg m^?2?yr^?1 and the uptake of macronutrients was in the order of K?>?N > Ca > P?>?Mg. The order of micronutrient removal (g m^?2?yr^?1) was Fe (0.2), Zn (0.08), Mn (0.06) and Cu (0.03). The soil fertility status at uniform management was above optimum. It is clear that leaf number, biomass partitioning and nutrient removal pattern had direct impact on flower stalk yields of gerbera.     

土壤碳氮对多年生能源草、覆盖作物和氮施肥的响应

Cover crop and nitrogen(N) fertilization may maintain soil organic matter under bioenergy perennial grass where removal of aboveground biomass for feedstock to produce cellulosic ethanol can reduce soil quality. We evaluated the effects of cover crops and N fertilization rates on soil organic carbon(C)(SOC), total N(STN), ammonium N(NH_4-N), and nitrate N(NO_3-N) contents at the0–5, 5–15, and 15–30 cm depths under perennial bioenergy grass from 2010 to 2014 in the southeastern USA. Treatments included unbalanced combinations of perennial bioenergy grass, energy cane(Saccharum spontaneum L.) or elephant grass(Pennisetum purpureum Schumach.), cover crop, crimson clover(Trifolium incarnatum L.), and N fertilization rates(0, 100, and 200 kg N ha~(-1)). Cover crop biomass and C and N contents were greater in the treatment of energy cane with cover crop and 100 kg N ha~(-1) than in the treatment of energy cane and elephant grass. The SOC and STN contents at 0–5 and 5–15 cm were 9%–20% greater in the treatments of elephant grass with cover crop and with or without 100 kg N ha~(-1)than in most of the other treatments. The soil NO_3-N content at 0–5 cm was 31%–45% greater in the treatment of energy cane with cover crop and 100 kg N ha~(-1)than in most of the other treatments.The SOC sequestration increased from 0.1 to 1.0 Mg C ha~(-1)year~(-1)and the STN sequestration from 0.03 to 0.11 Mg N ha~(-1)year~(-1)from 2010 to 2014 for various treatments and depths. In contrast, the soil NH_4-N and NO_3-N contents varied among treatments,depths, and years. Soil C and N storages can be enriched and residual NO_3-N content can be reduced by using elephant grass with cover crop and with or without N fertilization at a moderate rate.     

Nitrous oxide emissions and nitrogen cycling in managed grassland in Southern Hokkaido,Japan

Abstract

Nitrous oxide (N₂O) emissions were measured and nitrogen (N) budgets were estimated for 2?years in the fertilizer, manure, control and bare plots established in a reed canary grass (Phalaris arundinacea L.) grassland in Southern Hokkaido, Japan. In the manure plot, beef cattle manure with bark was applied at a rate of 43–44?Mg fresh matter (236–310?kg?N)?ha^?1?year^?1, and a supplement of chemical fertilizer was also added to equalize the application rate of mineral N to that in the fertilizer plots (164–184?kg?N?ha^?1?year^?1). Grass was harvested twice per year. The total mineral N supply was estimated as the sum of the N deposition, chemical fertilizer application and gross mineralization of manure (GMm), soil (GMs), and root-litter (GMl). GMm, GMs and GMl were estimated by dividing the carbon dioxide production derived from the decomposition of soil organic matter, root-litter and manure by each C?:?N ratio (11.1 for soil, 15.5 for root-litter and 23.5 for manure). The N uptake in aboveground biomass for each growing season was equivalent to or greater than the external mineral N supply, which is composed of N deposition, chemical fertilizer application and GMm. However, there was a positive correlation between the N uptake in aboveground biomass and the total mineral N supply. It was assumed that 58% of the total mineral N supply was taken up by the grass. The N supply rates from soil and root-litter were estimated to be 331–384?kg?N?ha^?1?year^?1 and 94–165?kg?N?ha^?1?year^?1, respectively. These results indicated that the GMs and GMl also were significant inputs in the grassland N budget. The cumulative N₂O flux for each season showed a significant positive correlation with mineral N surplus, which was calculated as the difference between the total mineral N supply and N uptake in aboveground biomass. The emission factor of N₂O to mineral N surplus was estimated to be 1.2%. Furthermore, multiple regression analysis suggested that the N₂O emission factor increased with an increase in precipitation. Consequently, soil and root-litter as well as chemical fertilizer and manure were found to be major sources of mineral N supply in the grassland, and an optimum balance between mineral N supply and N uptake is required for reducing N₂O emission.