The Effect of Mineral N Fertilization and Bradyrhizobium japonicum Seed Inoculation on Productivity of Soybean (Glycine max (L.) Merrill)

Soybean yields can be considerably improved by inoculation with selected Bradyrhizobium japonicum strains and fertilization. The aim of this study was to assess the productivity of two soybean cultivars depending on the applied N mineral fertilizers and seed inoculation with B. japonicum. The study showed that on average, for both cultivars, the soybean yield was most favorably affected by the combined use of inoculation and nitrogen fertilization (increase in seed yield by 42%, protein yield by about 28%). The application of mineral nitrogen at the dose of 30 or 60 kg·ha−1 allowed the increase in the seed yield by about 17% and protein content by about 14% compared to the control. Inoculation of soybean seeds with B. japonicum increased the yield of soybeans by about 20%, proteins by about 10% compared to the control, and inoculation of Hi®Stick Soy favored a better yield than Nitragina. Inoculation of seeds with Nitragina or Hi®Stick Soy and fertilization with mineral nitrogen increased the content of protein and fiber in seeds of both soybean cultivars, as well as reduced the amount of ash and fat. The seeds of cv. Aldana had a higher amount of protein and ash than cv. Annushka, but a similar amount of fat and fiber.

Nitrogen released from sago pulp waste and Gliricidia sepium pruning mixtures on a Dystrudept of Central Moluccas and its effect on the growth of maize

The agricultural sector is the mainstay of the economy in Central Moluccas. However, most agricultural soils on the island have low soil fertility. One of the efforts that farmers can make to improve soil fertility is to apply organic matter, which is widely found in Central Moluccas. This study aimed at elucidating the effect of mixing high-quality organic material (Glicidia sepium pruning) with low-quality organic material (sago pulp waste) on the improvement of available nitrogen in an acid soil (Dystrudept) and growth of maize. Two experiments were carried out in a laboratory and a greenhouse. The compositions of the mixtures of sago pulp waste (A) and pruning of Gliricidia sepium (G) were A0 G100; A20G80; A40G60; A60G40; A80G20, and A100G0. Six treatments and one control (no application of residues) were arranged in a completely randomized design. The results showed that the application of the mixture of 20% and 80% of Gliricidia sepium pruning (A20G80) increased the cumulative amount of mineral N in the soil higher than that of the other organic material mixtures, which in turn improved maize growth.

Metabolite shift in Medicago truncatula occurs in phosphorus deprivation

Symbiotic nitrogen fixation entails successful interaction between legume hosts and rhizobia that occur in specialized organs called nodules. N2-fixing legumes have higher demand of phosphorus (P) than legumes grown on mineral N. Medicago truncatula is an important model plant for characterization of effects of P deficiency at the molecular level. Hence, a study was carried out to address the alteration in metabolite levels of M. truncatula grown aeroponically and subjected to four weeks of P stress. First, GC-MS based untargeted metabolomics employed initially revealed changes in metabolic profile of nodules with increased levels of amino acids and sugars and decline in amounts of organic acids. Subsequently, LC-MS/MS was used to quantify these compounds including phosphorylated metabolites in overall plant. Our results showed drastic reduction in levels of organic acids and phosphorylated compounds in -P leaves with moderate reduction in -P roots and nodules. Additionally, sugars and amino acids were elevated in the whole plant under P deprivation. These findings provide evidence that N2-fixation in M. truncatula is mediated through N feedback mechanism that in parallel is related to C and P metabolism.

Use of Digestate as Organic Amendment and Source of Nitrogen to Vegetable Crops

Anaerobic digestion is a valuable process to use livestock effluents to produce green energy and a by-product called digestate with fertilising value. This work aimed at evaluating the fertilising value of the solid fraction (SF) of a digestate as an organic amendment and as a source of nitrogen to crops replacing mineral N. A field experiment was done with two consecutive vegetable crops. The treatments were: a control without fertilisation; Ni85 mineral fertilisation with 85 kg ha−1 of mineral N; fertiliser with digestate at an increasing nitrogen application rate (kg N ha−1): DG-N85 DG-N170, DG-N170+85, DG-N170+170; fertilisation with digestate together with Ni: DG-N85+Ni60, DG-N170+Ni60, DG-N170+Ni25. The results showed a soil organic amendment effect of the SF with a beneficial effect on SOM, soil pH and exchangeable bases. The SF was able to replace part of the mineral N fertilisation. The low mineralisation of the stable organic matter together with some immobilisation of mineral N from SF caused low N availability. The fertilisation planning should consider the SF ratio between the organic N (NO) and total N (TKN). Low NO:TKN ratios (≈0.65) needed lower Ni addition to maintaining the biomass production similar to the mineral fertilisation.

Varying Effects of Organic Waste Products on Yields of Market Garden Crops in a 4-Year Field Experiment under Tropical Conditions

Controlling organic and mineral fertilisation is a major concern in tropical environments. An experiment was conducted on an arenosol in the Dakar region, the main market gardening area of Senegal, to evaluate treatments commonly used by farmers. Seven treatments were repeated three times: A mineral fertilisation (MF) treatment based on N-P2O5-K2O (10-10-20), and three organic treatments at two doses (dried sewage sludge (SS), poultry litter (PL) and a digestate from an anaerobic digestion (AD) of cow manures). Each of the organic treatments were supplemented with a normal dose (1) and a double dose (2) of mineral N and K fertiliser. A lettuce, carrot and tomato rotation was grown in four campaigns (2016–2020) on all of the plots. Yields of all three crops in all of the organic treatments were statistically similar (p > 0.05) to the MF in all four campaigns, except for the yield of the lettuce crop under treatment PL-2 in campaigns 2 and 3. The tomato yields were statistically similar under all of the organic treatments in all four campaigns. In contrast, the yields of the lettuce and carrot crops differed statistically from each other and under the different organic treatments in all four campaigns. The yields of all three crops differed in the campaigns with the fertilisation treatment. In each campaign, the yields of each crop were not correlated with the total amounts of N, P and K applied. These differences or similarities in yields are explained by the nature of the organic waste products, the accumulation of nutrients after several applications, the type of crop and interannual differences in temperature.

Carbon and Nitrogen Dynamics in Mexican Management Forest: Simulation of Biomass Harvesting and C and N Amendments

Sustainable silvicultural management requires the maintenance of long-term ecosystem processes. We used the CENTURY model to simulate the impact of wood extraction and organic amendments on aboveground biomass, carbon (C) storage, and the availability of nitrogen (N) in the two dominant silvicultural methods in Mexico: the silvicultural development method (SDM) and irregular forest management (IFM). The values of the mean absolute percentage error for the SDM and IFM were 2.1% and 3.3% for C in aboveground biomass, 5.7% and 5.0% for soil organic carbon (SOC), and 14.9% and 21.6% for N, respectively. Simulation for the SDM (1967–2068) suggested a reduction of ~7% in C in soil, microbial biomass, and litter, 9% in aboveground biomass C, and ~20% in the mineral N available. For IFM, the simulation (2009–2019) suggested a reduction of 14% in the accumulation of aboveground biomass and 13% in the mineral N available. Simulation of the adoption of management practices suggested that N mineral availability would increase by 2%–3% without drastically reducing the SOC, improving aboveground biomass production by ~7%, in each management system. Study Implications In Mexico, current silvicultural management is causing alterations in the biological and chemical processes of the soil, but the future impacts on the production of forest wood and loss of fertility cannot be estimated by direct measurements. We simulated two silvicultural management alternatives with two rotation cycles and measured the response in terms of SOC, nitrogen availability, and aboveground biomass. The model shows that improving forest residue management by adding organic amendments to the soil would counteract changes in soil microbial activity, nitrogen availability, SOC, and aboveground biomass in the future. Managers should consider this information to reorient current crop residue management to achieve the objectives and the sustainability of forest management in Mexican temperate forests.

Nitrogen Fertiliser Immobilisation and Uptake in the Rhizospheres of Wheat and Canola

Immobilisation of fertiliser nitrogen (N) by soil microorganisms can reduce N availability to crops, decreasing growth and yield. To date, few studies have focussed on the effect of different plant species on immobilisation of fertiliser N. Canola (Brassica napus) is known to influence the soil microbiome and increase mineral N in soil for future crops compared with cereals. We tested the hypothesis that canola can reduce immobilisation of fertiliser N by influencing the composition of the rhizosphere microbiome. To investigate this, we conducted a glasshouse soil column experiment comparing N fertiliser uptake between canola and wheat (Triticum aestivium) and partitioning of fertiliser N between plants and microorganisms. Plants were grown in soil to which high C:N ratio wheat residues and 15N-labelled urea fertiliser were applied. There was no difference between wheat and canola in fertiliser N uptake despite differences in fungal community composition and the carbon metabolising enzyme alpha-glucosidase in the rhizosphere. Canola obtained more soil-derived N than wheat. There was no significant difference in the rhizosphere bacterial communities present between wheat and canola and unplanted controls. Our results highlight the capacity of canola to increase mineralisation of soil N compared with wheat although the study could not describe the microbial community which facilitated this increase.

A review of the importance of mineral nitrogen cycling in the plant-soil-microbe system of permafrost-affected soils – changing the paradigm

The paradigm that permafrost-affected soils show restricted mineral nitrogen (N) cycling in favor of organic N compounds is based on the observation that net N mineralization rates in these cold climates are negligible. However, we find here that this perception is wrong. By synthesizing published data on N cycling in the plant-soil-microbe system of permafrost ecosystems we show that gross ammonification and nitrification rates in active layers were of similar magnitude and showed a similar dependence on soil organic carbon (SOC) and total nitrogen (TN) concentrations as observed in temperate and tropical systems. Moreover, high protein depolymerization rates and only marginal effects of C:N stoichiometry on gross N turnover provided little evidence for N limitation. Instead, the rather short period when soils are not frozen is the single main factor limiting N turnover. High gross rates of mineral N cycling are thus facilitated by released protection of organic matter in active layers with nitrification gaining particular importance in N-rich soils, such as organic soils without vegetation. Our finding that permafrost-affected soils show vigorous N cycling activity is confirmed by the rich functional microbial community which can be found both in active and permafrost layers. The high rates of N cycling and soil N availability are supported by biological N fixation, while atmospheric N deposition in the Arctic still is marginal except for fire-affected areas. In line with high soil mineral N production, recent plant physiological research indicates a higher importance of mineral plant N nutrition than previously thought. Our synthesis shows that mineral N production and turnover rates in active layers of permafrost-affected soils do not generally differ from those observed in temperate or tropical soils. We therefore suggest to adjust the permafrost N cycle paradigm, assigning a generally important role to mineral N cycling. This new paradigm suggests larger permafrost N climate feedbacks than assumed previously.

Temporal Monitoring and Assessment of Inorganic Nitrogen Content of Soil due to Nitrogen Fertilizers and their Related Cytotoxic Effects

Background: Indian economy is largely based on agriculture. Major share of agricultural investments goes into chemical fertilizers. Nitrogen (N) fertilizers are used in fields to enhance the crop yield. Most of the reports are based on growth related data, morphological and yield related data but very few reports reveal the facts about genotoxic and cytotoxic effects of these fertilizers. Therefore, the present communication is an attempt in the aforesaid direction. Methods: In a pot experiment, mineral N content of soil in the form of ammonium-N (NH4+-N) and nitrate-N (NO3--N) were analysed at regular interval of 5 days till 30 days after treatment (DAT). On the corresponding days root tip assay was done for cytotoxic analyses and also the temporal changes in NH4+-N and NO3--N contents were observed. Result: In the Ammonium nitrate treatments, higher mitotic index (MI%) percentages were obtained. While for the Urea, NH4+-N content and MI were found to have a positive correlation. Also, it was found that there is an optimum ratio of NH4+-N and NO3--N in each treatment at which the MI% was the maximum. The study gives an interesting insight for the possible cytotoxic effects of the N fertilizers.