Nitrogen Immobilisation and Microbial Biomass Build-Up Induced by Miscanthus x giganteus L. Based Fertilisers

Cultivation of Miscanthus x giganteus L. (Mis) with annual harvest of biomass could provide an additional C source for farmers. To test the potential of Mis-C for immobilizing inorganic N from slurry or manure and as a C source for soil organic matter build-up in comparison to wheat (Triticum aestivum L.) straw (WS), a greenhouse experiment was performed. Pot experiments with ryegrass (Lolium perenne L.) were set up to investigate the N dynamics of two organic fertilisers based on Mis at Campus Klein-Altendorf, Germany. The two fertilisers, a mixture of cattle slurry and Mis as well as cattle manure from Mis-bedding material resulted in a slightly higher N immobilisation. Especially at the 1st and 2nd harvest, they were partly significantly different compared with the WS treatments. The fertilisers based on Mis resulted in a slightly higher microbial biomass C and microbial biomass N and thus can be identified as an additional C source to prevent nitrogen losses and for the build-up of soil organic matter (SOM) in the long-term.

Changes in Nitrogen Pools in the Maize—Soil System after Urea or Straw Application to a Typical Intensive Agricultural Soil: A 15N Tracer Study

A maize pot experiment was conducted to compare the difference of N distribution between bulk and rhizospheric soil after chemical fertilizer with or without soil straw amendment at an equivalent N rate using a 15N cross-labeling technique. Soil N pools, maize N and their 15N abundances were determined during maize growth. The urea plus straw treatment significantly (p < 0.05) increased the recovery of urea N in soil and 26.0% of straw N was assimilated by maize. Compared with urea treatment in bulk soil, urea plus straw treatment significantly (p < 0.05) increased the concentration and percentage of applied N as dissolved organic N (DON) and microbial biomass N (MBN) from milk stage to maturity, increased those as particulate organic N (PON) and mineral associated total N (MTN) throughout maize growth and decreased those as inorganic N (Inorg-N) from the eighth leaf to the silking stage. Compared with bulk soil, rhizospheric soil significantly (p < 0.05) decreased the concentration and percentage of applied N as PON and increased those as Inorg-N and MTN in both applied N treatments from the silking stage, and significantly (p < 0.05) decreased the concentration and percentage of applied N as microbial biomass N (MBN) in the urea plus straw treatment. Overall, straw N was an important N source and combined application of chemical fertilizer with straw increased soil fertility, with the rhizosphere regulating the transformation and supply of different N sources in the soil–crop system.

Evaluation of biochars as carriers for Rhizobium leguminosarum

Peat is the standard carrier material used for commercial microbial inoculants produced in Canada and the United States. Peat is a slowly renewable resource and its production is extremely vulnerable to variable weather conditions. Furthermore, it may not be widely available in all countries. We investigated the potential to develop biochar as a carrier material. Our goal was to evaluate if different biochars perform comparably in supporting rhizobial survival, and what characteristics contribute to their ability to support rhizobial survival. Evaluation included characterization of the biochars, assessment of biochar phytotoxicity, survival of Rhizobium on biochars, and growth chamber evaluation of two biochars as Rhizobium carriers for inoculating pea. Of the original nine biochars evaluated, six supported Rhizobium leguminosarum for 84 days at 4 °C; of this six, two supported numbers >1 × 106 cfu·(g biochar)−1. The only characteristics that correlated with survival were C/N ratio and percent C. The two biochars evaluated delivered R. leguminosarum to pea that initiated nodulation, biomass production, and biomass N at levels higher than a noninoculated control and heat-killed inoculated biochars. We demonstrate that there is considerable potential to develop biochar as a carrier for rhizobial inoculants.

Effect of straw and inhibitors on the fate of nitrogen applied to paddy soil

A pot experiment was used to explore the distribution of fertilizer N and agronomic effects in a paddy soil-rice (Oryza sativa L.) system. Five treatments were set: without nitrogen, straw and inhibitor (C), urea (U), urea + straw (US), urea + urease + nitrification inhibitor (UI) and urea + urease + nitrification inhibitor + straw (UIS). Soil and urea-derived microbial biomass N increased significantly in US and UIS compared with straw-free treatments at seedling and tillering, indicating that biotic process play an important role in the retention of fertilizer N with straw addition. About 10% urea-N was recovered as fixed ammonium (FA) at seedling stage, subsequently released at tillering and maturation regardless of treatments, which emphasizes the importance of FA in the retention and supply of fertilizer N in paddy soils. Compared with U, rice yield and N uptake in US decreased by 7.8% and 25.2% respectively, while inhibitors (UIS) alleviated the reduction by 16.4% and 31.6%. The current research indicated UIS is recommended as the most appropriate management strategy in paddy soils of Northeast China based on N dynamics. But the economic effect as well as the field-scale validation need to be further evaluated.

N, S, O Self-Doped Porous Carbon Nanoarchitectonics Derived from Pinecone with Outstanding Supercapacitance Performances

Biomass-derived porous carbons are considered as one of the most promising electrode materials for supercapacitors due to their low-cost and natural abundance. In this work, pinecone is used to fabricate biomass N, S, O-doped porous carbon via one-step carbonization process with KOH activation. By optimizing the additive amount of KOH and calcination temperature, the asprepared product shows a high specific surface area and pore volume up to 1593.8 m2 g−1 and 0.8582 cm3 g−1, respectively. As an electric double-layer capacitor (EDLC) electrode, the N, S, O-doped porous carbon exhibits a high specific capacitance of 285 F g−1 at 0.5 A g−1 and good rate performance with a capacitance retention of 78.6% from 0.5 to 20 A g−1. Furthermore, the as-assembled symmetric supercapacitor with 6 mol L−1 KOH as electrolyte possesses a promising energy density of 6.34 Wh kg−1 and a power density of 250 W kg−1. Outstanding cycling stability was also demonstrated with 94.4% capacitance retention after 10,000 charge/discharge cycles at 1 A g−1.

Pennycress as a Cash Cover-Crop: Improving the Sustainability of Sweet Corn Production Systems

Commercial sweet corn (Zea mays convar. saccharata var. rugosa) production has a proportionally high potential for nutrient loss to waterways, due to its high nitrogen (N) requirements and low N use efficiency. Cover crops planted after sweet corn can help ameliorate N lost from the field, but farmers are reluctant to utilize cover crops due to a lack of economic incentive. Pennycress (Thlaspi arvense L.) is a winter annual that can provide both economic and environmental benefits. Five N-rates (0, 65, 135, 135 split and 200) were applied pre-plant to sweet corn. After the sweet corn harvest, pennycress was planted into the sweet corn residue with two seeding methods and harvested for seed the following spring. Residual inorganic soil N (Nmin), pennycress biomass, biomass N and yield were measured. The nitrogen rate and seeding method had no effect on pennycress yield, biomass, or biomass N content. The nitrogen rate positively affected Nmin at pennycress seeding, wherein 200N plots had 38–80% higher Nmin than 0N plots, but had no effect on Nmin at pennycress harvest. Control treatments without pennycress had an average of 27–42% greater Nmin. In conclusion, pennycress can act as an effective N catch crop, and produce an adequate seed yield after sweet corn without the need for supplemental fertilization.

Climatic, Edaphic and Biotic Controls over Soil δ13C and δ15N in Temperate Grasslands

Soils δ13C and δ15N are now regarded as useful indicators of nitrogen (N) status and dynamics of soil organic carbon (SOC). Numerous studies have explored the effects of various factors on soils δ13C and δ15N in terrestrial ecosystems on different scales, but it remains unclear how co-varying climatic, edaphic and biotic factors independently contribute to the variation in soil δ13C and δ15N in temperate grasslands on a large scale. To answer the above question, a large-scale soil collection was carried out along a vegetation transect across the temperate grasslands of Inner Mongolia. We found that mean annual precipitation (MAP) and mean annual temperature (MAT) do not correlate with soil δ15N along the transect, while soil δ13C linearly decreased with MAP and MAT. Soil δ15N logarithmically increased with concentrations of SOC, total N and total P. By comparison, soil δ13C linearly decreased with SOC, total N and total P. Soil δ15N logarithmically increased with microbial biomass C and microbial biomass N, while soil δ13C linearly decreased with microbial biomass C and microbial biomass N. Plant belowground biomass linearly increased with soil δ15N but decreased with soil δ13C. Soil δ15N decreased with soil δ13C along the transect. Multiple linear regressions showed that biotic and edaphic factors such as microbial biomass C and total N exert more effect on soil δ15N, whereas climatic and edaphic factors such as MAT and total P have more impact on soil δ13C. These findings show that soil C and N cycles in temperate grasslands are, to some extent, decoupled and dominantly controlled by different factors. Further investigations should focus on those ecological processes leading to decoupling of C and N cycles in temperate grassland soils.

Maturity indices of composting plant materials with Trichoderma asperellum as activator

Compost maturity is a major factor in its use for nutrient supply without adverse effect on crop germination. Composting may be accelerated with inclusion of some microorganisms as activators. This study was conducted to determine the effect of Trichoderma asperellum and length of composting of different plant materials and cattle manure on compost maturity in Ibadan, Nigeria. Composting of two plant materials with cow dung at ratio 3:1 was done in triplicate with or without Trichoderma activation to obtain twelve heaps of four different types of composts; Panicum-based compost with Trichoderma, Tridax-based compost with Trichoderma, Panicum-based compost without Trichoderma and Tridax-based compost without Trichoderma. The process was a 2×2 factorial experiment, laid out a completely randomized design. The Trichoderma activated compost (TAC) at four weeks of composting (4WC) had 56% total N, 21% organic matter, 38% total K, 51% total P and 66.6% microbial biomass N increase over non-activated compost (NAC). Carbon to nitrogen ratio was within the ideal range (10–20) in TAC while it was greater than it in NAC. Microbial biomass and lignin contents had a 56% and 41% increase, respectively, in NAC over TAC. Trichorderma-activated compost has a potential to hasten maturation and makes the compost ready for field on or before four weeks without posing a threat to crop germination.

Comparative Transcriptome Analysis in Oilseed Rape (Brassica napus) Reveals Distinct Gene Expression Details between Nitrate and Ammonium Nutrition

Nitrate (NO3−) and ammonium (NH4+) are the main inorganic nitrogen (N) sources absorbed by oilseed rape, a plant that exhibits genotypic differences in N efficiency. In our previous study, the biomass, N accumulation, and root architecture of two oilseed rape cultivars, Xiangyou 15 (high N efficiency, denoted “15”) and 814 (low N efficiency, denoted “814”), were inhibited under NH4+ nutrition, though both cultivars grew normally under NO3− nutrition. To gain insight into the underlying molecular mechanisms, transcriptomic changes were investigated in the roots of 15 and 814 plants subjected to nitrogen-free (control, CK), NO3− (NT), and NH4+ (AT) treatments at the seedling stage. A total of 14,355 differentially expressed genes (DEGs) were identified. Among the enriched Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway categories of these DEGs, carbohydrate metabolism, lipid metabolism, protein metabolism, and cell wall biogenesis were inhibited by AT treatment. Interestingly, DEGs such as N transporters, genes involved in N assimilation and CESA genes related to cellulose synthase were also mostly downregulated in the AT treatment group. This downregulation of genes related to crucial metabolic pathways resulted in inhibition of oilseed rape growth after AT treatment.