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.

Improvement of Nitrogen-Fertilizer Recommendation by Consideration of Long-Term Site and Cultivation Effected Mineralization

Organic matter (OM) and nutrient nitrogen (N) play vital roles in the fertility and production of soil in accordance with goals of efficient environmental protection. This study aimed to show the extent to which N delivery can contribute to improving nitrogen fertilizer requirements (NFR) through comparative analysis of OM and N. Systems determining the NFR in agricultural practices have thus far been challenged to estimate the annual rate of mineralization of the soil. OM and N turnover was investigated through an available evaluation consisting of 546 representatively distributed permanent test and observation plots (TP) of the German Federal State of Saxony farms. A solid database of at least 10-year field plot card records from 2001 to 2010 was selected for the analysis. A program (BEFU) widely used in agricultural practice, along with the simplified process model CCB, were applied. For the calculation of the amount of mineral N fertilizers used, the results of three different methods for determining the NFR were compared with each other. The determination of the farmers’ demand (=actual condition of the TP) with a mean value of 132 kg N ha−1 did not show a large difference between the calculated values with 137 kg N ha−1 by the BEFU program. Based on the available results for the most important crop species cultivated in Saxony, there were clear differences in the considerations of the N delivery from the soil. The BEFU program was able to calculate an average N delivery of 17 kg N ha−1 from tabulated data, whereas with the CCB process model, 66 kg N ha−1 of mineralization was determined with a distinct higher deviation by taking into account the 10-year field histories. Using the N delivery of the TP by the CCB model, a clear reduction of the mean N fertilization level, to about 80 kg N ha−1, was therefore achieved. These differences were particularly large for TP with organic fertilization (livestock), at a relatively low N fertilization level, and for certain crop species. With a high standard deviation, the average savings potential of mineral N fertilizers was 52–57 kg N ha−1. After including the corrected values for the N mineral fertilization, a decrease in the N balances by an average of 20–25 kg N ha−1 was ultimately achieved. In particular, the heavily oversupplied plots with D and E classification decreased by approximately 50%. The results of our study demonstrate clear improvements; therefore, increased efforts should be made in the future to optimize the determination of NFR using applicable methods that consider N mineralization in agricultural practice and consultation.

Rhizobial–Host Interactions and Symbiotic Nitrogen Fixation in Legume Crops Toward Agriculture Sustainability

Symbiotic nitrogen fixation (SNF) process makes legume crops self-sufficient in nitrogen (N) in sharp contrast to cereal crops that require an external input by N-fertilizers. Since the latter process in cereal crops results in a huge quantity of greenhouse gas emission, the legume production systems are considered efficient and important for sustainable agriculture and climate preservation. Despite benefits of SNF, and the fact that chemical N-fertilizers cause N-pollution of the ecosystems, the focus on improving SNF efficiency in legumes did not become a breeder’s priority. The size and stability of heritable effects under different environment conditions weigh significantly on any trait useful in breeding strategies. Here we review the challenges and progress made toward decoding the heritable components of SNF, which is considerably more complex than other crop allelic traits since the process involves genetic elements of both the host and the symbiotic rhizobial species. SNF-efficient rhizobial species designed based on the genetics of the host and its symbiotic partner face the test of a unique microbiome for its success and productivity. The progress made thus far in commercial legume crops with relevance to the dynamics of host–rhizobia interaction, environmental impact on rhizobial performance challenges, and what collectively determines the SNF efficiency under field conditions are also reviewed here.

Enhanced Cd Phytoextraction by Solanum Nigrum L From Contaminated Soils Combined With the Application of N Fertilizers and Double Harvests

It is very important to increase phytoremediation efficiency in practice in suitable climatic conditions for plant growth by multiple harvests. Solanum nigrum L. is a Cd hyperaccumulator. In present experiment, after applying different types of N fertilizers (NH4HCO3, NH4Cl, (NH4)2SO4, CH4N2O), root and shoot biomasses and Cd phytoextraction efficiency of S. nigrum effectively improved (P < 0.05), whereas shoot biomasses of S. nigrum harvested at the first florescence stage plus the amounts at the second florescence stage were higher than those at the maturation stage, which indicated that S. nigrum Cd phyto-accumulation efficiency was higher in double harvests at florescence stages compared to a single harvest due to the lack of a clear change in Cd concentration (P < 0.05). The pH value and extractable Cd contents showed no changes, regardless whether N fertilizer was added or not at different growth stages. In addition, after N fertilizer supply, H2O2 and MDA contents in S. nigrum in vivo were lower compared to CK; Similarly, the concentration of proline was decreased as well (P < 0.05). As one of the antioxidant enzymes, CAT activity in S. nigrum shoots, harvested at different growth periods after 4 types of N fertilizer application, obviously decreased, while POD and SOD activities increased (P < 0.05). Our study demonstrated that (NH4)2SO4 treatment exerted the most positive effect and the CH4N2O the second-most positive effect effect on S. nigrum Cd phytoremediation efficiency in double harvests at florescence stages and the growth conditions were better than others.

Performance, Phyto-nutritional and Bio-active substances of Sweet Pepper (Capsicum annum) in response to Soil Applied Organic and Inorganic Sources of N Fertilizers

Background: Soil health is an important factor for producing a higher yield and obtaining good quality products. Nitrogen fertilizer is one of the most important and valuable agricultural inputs for increasing crop production. Objective: Experiments were conducted in 2017 and 2018 in the cropping seasons to determine the performance and nutritional qualities of sweet pepper in response to organic and inorganic sources of N fertilizers. Methods: Ten kilograms (10 kg) capacity black polythene bags were filled with topsoil and were arranged randomly on the field. Treatment combination included: - 0 NPK + 0 PM (T1), 40 NPK + 0 PM (T2), 32 NPK + 8 PM (T3), 24 NPK + 16 PM (T4), 0 NPK + 40 PM (T5), 8 NPK + 32 PM (T6), 16 NPK + 24 PM (T7) and 20 NPK + 20 PM (T8). Experiments were laid out in a completely randomized design and were replicated four times. Vegetative, flowering, and quality parameters were collected and analyzed using the GenStat Discovery, 2014 statistical analysis software. Separation of means was determined by the Duncan Multiple Range Test (DMRT) at a probability level of 5%. Results: Results indicated that high rates of an organic source of N fertilizer produced higher values for vegetative and yield parameters, which was similar to the sole application of inorganic fertilizer. There was no significant effect of the sole application and combined organic and inorganic sources of N fertilizer on heavy metals and nitrates accumulation, but their effects were able to increase the values for nitrites above the recommended limits as suggested by the Joint FAO/WHO Expert Committee on Food Additives. Conclusion: Our results showed that 20 NPK + 20 PM is the best treatment without any health implications in the study area, which also improved the yield and, therefore, can be considered economical.

Effects of Enhanced-Efficiency Nitrogen Fertilizers on Soil Microbial Biomass and Respiration in Tropical Soil Under Upland Rice Cultivation

While over-use of N fertilizers can suppress microbial biomass, application of urease inhibitors is known to be a potential way to rebuilt microbial diversity and improve soil functions. However, the hypothesis of this study is that the application of N fertilizers regardless of the source would increase soil microbial biomass and reduce soil respiration. A two-year field experiment was conducted to assess the effects of enhanced-efficiency N sources on soil microbial biomass, and soil respiration. The experiment was set up in a randomized block design in a 3 &times; 4 + 1 factorial scheme, with four replicates. Treatments comprised three sources (conventional uncoated urea, NBPT (N-(n-butyl) thiophosphoric triamide)-treated urea, and polymer-coated urea) and four rates (30, 60, 90 and 120 kg ha-1) of N, in addition to a control treatment (no fertilizer application). Microbial biomass C (MBC) and microbial biomass N (MBN), and soil respiration (C-CO2 and qCO2) were determined in upland rice rhizosphere in each crop season. Responses of soil microbial properties to N fertilization were dependent on the N rates, but no significant effect of the N sources was observed. All measured parameters, except MBC in the first season and C-CO2 in the second season, were increased with increasing N rates. However, the application of N higher than 60 kg ha-1 suppressed soil microbial biomass, as well as soil respiration. &nbsp;Therefore, the lack of response by added urease inhibitors to the N sources indicate that optimizing N rates for upland rice production is a far more effective option for improving soil microbial community than using enhanced-efficiency N sources.