Chemical Nitrogen Fertilizer Application Research Articles

Organic waste recycling application increases N availability and mitigates N2O emission without crop yield penalty in the North China Plain.

Agricultural organic waste recycling can supply nutrients for crop production and partially replace chemical nitrogen fertilizers, which is beneficial for waste management and environmental protection. Nevertheless, comprehensive evaluation of the effects of different organic materials applications on crop yield and the environment is limited. Therefore, in this study, a comprehensive investigation of the synergistic effects of straw, pig manure, and biogas residue recycling on the wheat (Triticum aestivum L.) and maize (Zea mays L.) systems was carried out in the North China Plain. Field experiments were conducted from 2019 to 2021, comprising five treatments: straw (ST), pig manure (PM), and biogas residue (BR) partially replacing chemical nitrogen fertilizer, sole application of chemical nitrogen fertilizer (CF), and a control with no nitrogen application (WN). The results showed that organic materials significantly increased soil total nitrogen (3.04%-9.10%) and N recovery efficiency (REN; 42.21%-44.99%), but pig manure was more beneficial in increasing crop yields (3.50%), especially wheat yields (8.72%), and REN was significantly higher than that of the other treatments. Organic materials performed differently in wheat and maize seasons, and wheat yield could be improved by organic materials return. Organic materials stimulated N2O emission in wheat season (4.28%-32.20%), while biogas residue inhibited the N2O emission in maize season (47.47%). The negative effect of straw and biogas residue on yield decreased with increasing years of return, and pig manure continued to contribute to yield. In conclusion, pig manure is the optimal alternative that can increase crop yield, soil N content, and REN without stimulating N2O emissions.

Effects of Biochar-loaded Ammonia Nitrogen on Soil Carbon Emissions, Enzyme Activity, and Microbial Communities

The form of soil nitrogen input significantly affects soil CO2 emission. As a new form of nitrogen input, biochar-loaded ammonia nitrogen not only reduces the input of chemical nitrogen fertilizer in farmland but also reduces the cost of environmental treatment. It is of great significance to promote the zero growth of national chemical fertilizer, the prevention and control of farmland non-point source pollution, and the realization of the national goal of "carbon peak" and "carbon neutralization." Through an indoor culture experiment, the effects of different nitrogen input forms on soil carbon emission, enzyme activity, and microbial community were studied through four treatments:no fertilization (CK), single application of chemical nitrogen fertilizer (CF), biochar combined application of chemical nitrogen fertilizer (BF), and biochar-loaded ammonia nitrogen (BN). The results showed that compared with that in CF, BF significantly increased cumulative carbon emissions (66.24 %), whereas BN had no significant difference. It is worth noting that the cumulative carbon emissions were significantly reduced by 35.28 % compared with that in BF and BN. Compared with those in CF and BF, the activities of β-glucosidase, peroxidase, and polyphenol oxidase treated with BN significantly increased by 20.25 % and 5.20 %, respectively. Compared with that in CF, the BF treatment increased microbial community richness and community diversity, whereas the BN treatment decreased microbial community richness. Compared with that in BF, the relative abundance of Proteobacteria decreased by 11.16 %, and the relative abundance of Actinobacteria and Bacteroidota increased by 8.12 % and 5.83 %, respectively, in which xylosidase activity was the most important soil factor affecting microbial community structure. The relative abundance of Chloroflexi was significantly correlated with cellobiose hydrolase activity, and the relative abundance of Gemmatimonadetes was significantly correlated with β-glucosidase activity. There was a very significant correlation between the relative abundance of Proteobacteria and cumulative carbon emissions. To summarize, compared with those under biochar combined with chemical nitrogen fertilizer, biochar loaded with ammonia nitrogen significantly reduced cumulative carbon emissions, and its emission reduction effect was better. The results of this study will be beneficial to the landing of the national "double carbon strategy," the healthy development of the biological natural gas industry, the construction of the national green cultivation circular agriculture system, and the realization of the national zero growth strategy of chemical fertilizer.

Effects of Biochar-Coated Nitrogen Fertilizer on the Yield and Quality of Bok Choy and on Soil Nutrients

This study was aimed at problems associated with low fertilizer using efficiency, excessive nitrate content of vegetables, and soil degradation in greenhouse vegetable production. A pot experiment was conducted to assess the effects of applying biochar-coated nitrogen fertilizer (BCNF) on the yield, quality, and nitrate content of bok choy (Brassica rapa subsp. Chinensis) as well as on soil nutrients in greenhouses. Four treatments were set up as follows: no nitrogen fertilizer application (BA), chemical nitrogen fertilizer application (CK), biochar-coated nitrogen fertilizer application (BCNF, the amount of nitrogen was equal to that of chemical fertilizer), and reduced biochar-coated nitrogen fertilizer application (D-BCNF, the amount of fertilizer was 80% of BCNF). Compared with the other treatments, BCNF treatment increased chlorophyll content, plant height, maximum leaf length, maximum leaf width, and other biological characters of bok choy. Compared with CK treatment, BCNF treatment increased the fresh weight of bok choy by 14.02%, while reducing the root–shoot ratio and nitrate content by 19.1% and 46%, respectively. It was further found that the application of BCNF could effectively increase the content of soil organic matter; reduce the leaching loss of nitrate nitrogen, exchangeable calcium and magnesium; and effectively improve nitrogen use efficiency. Therefore, the application of BCNF can not only reduce the loss of fertilizer nutrients, promote plant growth, and improve fertilizer utilization, but it can also improve soil nutrients, fix carbon, and reduce emissions. It is a new type of environmental protection fertilizer with application prospects.

Maize-soybean intercropping improved maize growth traits by increasing soil nutrients and reducing plant pathogen abundance

IntroductionMaize (Zea mays L.)–soybean (Glycine max L.) intercropping has been widely utilized in agricultural production due to its effectiveness in improving crop yield and nutrient use efficiency. However, the responses of maize rhizosphere microbial communities and the plant pathogen relative abundance to maize growth traits in maize-soybean intercropping systems with different chemical nitrogen fertilizer application rates remain unclear.MethodsIn this study, a field experiment was conducted, and the bacterial and fungal communities of maize rhizosphere soils in maize-soybean intercropping systems treated with different N fertilization rates were investigated using Illumina NovaSeq sequencing. Maize growth traits, soil physicochemical properties and soil enzyme activities were also examined.Results and discussion:We found that intercropping and N fertilizer treatments strongly influenced soil microbial diversity, structure and function. The PLSPM (partial least squares path modeling) confirmed that soil nutrients directly positively affected maize biomass and that intercropping practices indirectly positively affected maize biomass via soil nutrients, especially NH4+-N. Intercropping agronomic approaches also improved maize growth traits by reducing the plant pathogen abundance, and the relative abundance of the plant pathogen Trichothecium roseum significantly decreased with intercropping treatments compared to monocropping treatments. These results confirmed the benefits of maize-soybean intercropping treatments for agricultural production.

Synergistic impacts of climate change and human activities on spatiotemporal organic nitrogen burial variation in a plateau lake in southwest China

ABSTRACT The concentration and sources of organic nitrogen (ON) in lake sediments affect lake nitrogen cycles. However, the factors influencing ON accumulation rate (ONAR) are unclear. We collected 3 sediment cores from northern, eastern, and southern Dianchi Lake (DC-N, DC-E, and DC-S, respectively) in July 2014, to study the effects of autochthonous and allochthonous sources of ON. The ON and ONAR increased 2.4–5.1 and 2.6–4.8 times, respectively, from 1900 to 2000, especially since the 1980s, when algal blooms have occurred more frequently. The ON decreased in the order DC-S > DC-N > DC-E, whereas the ONAR decreased in the order DC-N > DC-S > DC-E, suggesting that ONAR was influenced by ON content as well as the depositional environment. The total concentrations of n-alkanes (n-C12 to n-C34) ranged from 4719 to 61 960 ng g−1 in the 3 sediment cores, with proportions varying with vertical depth. The sources of ON were mainly allochthonous (soil erosion and terrestrial plants) and autochthonous (algal and aquatic plants) in DC-S and DC-N, respectively, and primarily mixed planktonic and terrestrial in DC-E. The stochastic impacts by regression on population, affluence, and technology (STIRPAT) model revealed that a 1% increase in air temperature and nitrogen fertilizer corresponded to an increase in ONAR by 23–33% and 20–79% in the Dianchi Lake basin, especially in DC-S and DC-E. However, a 1% increase in urban land area reduced ONAR by 2–11%, especially in DC-N. Our study suggests that the spatial and temporal ONAR in Dianchi Lake may increase in response to a warmer and wetter climate combined with increasing chemical nitrogen fertilizer application.

Distribution and sequestration of straw carbon in surface and deep soil aggregates under different fertilization treatments

Long-term fertilization causes the differences in water, heat, nutrients and microbial activities between topsoil and deep soil, with consequences on the decomposition and turnover of straw carbon (C) in soils. At a long-term positioning experimental station in Shenyang Agricultural University, we mixed the topsoil (0-20 cm) and deep soil (40-60 cm) samples from different fertilization treatments with 13C-labeled straw for in-situ incubation. We analyzed the content of organic C and its δ13C value in soil aggregates, compared the difference in the distribution of straw C between topsoil and deep soil aggregates, and explored the effects of fertilization on the sequestration of straw C in soil aggregates. Compared with fertilization treatments (i.e., single chemical nitrogen fertilizer application and combination of organic manure with nitrogen fertilizer application), the treatment without fertilization increased the content of straw C of <0.053 mm aggregate in the topsoil by 106.7% and that of >0.25 mm aggregate in the deep soil by 34.2%. The contribution percentage of straw C to organic C of >0.053 mm aggregate in the deep soil was about two times of that in the topsoil. About 22.6% and 11.4% of straw C was distributed into the >0.25 mm and <0.25 mm aggregates of topsoil, and about 29.4% and 8.8% of straw C was distributed into the >0.25 mm and <0.25 mm aggregates of deep soil, respectively. In conclusion, straw addition promoted the regeneration and sequestration of carbon in deep soil macroaggregates and increased the carbon sequestration potential of deep soil.

Agricultural soil management to reduce N2O emission

N2O is a greenhouse gas with a radiative forcing 298 times that of CO2 and is the substance that contributes most to the destruction of the stratospheric ozone layer. Current global N2O emission from the earth surface is 18.5 Tg y−1. Soil N2O emission is 13 Tg y−1, in which agricultural soil N2O emission accounts for 7 Tg y−1. N2O is produced as byproduct during nitrification process and interim product during denitrification process, mainly produced by denitrification in soils with increasing fertilizer application, as evidenced in agricultural fields. N2O emission increased significantly during the practices of fertilizer application, compost application, and harvesting, and peaked at a soil temperature of 20 °C or higher and a water-filled pore space of 60-70%. N2O emissions increased due to a decrease in soil pH. Soil pH tended to increase with the application of compost, and N2O in the compost plot decreased over time compared to the chemical fertilizer plot. This is because the optimal pH of incomplete denitrifying bacteria causing nitrous oxide emission is lower than that of complete denitrifying bacteria. Therefore, it is recognized that the pH should be 6.5 or more to suppress the N2O. In order to make better handling of compost, compost pellet has been developed, because it was found that nitrogen addition into compost pellet reduces N2O emission. N2O emission is related to the amount of inorganic nitrogen in soil. N2O emission increases with organic matter decomposition in soil and nitrogen fertilizer application. In organic soil (peat), huge N2O emission of several 100 kgN ha−1 y−1 was found in vegetable fields in a tropical peat land. Organic matter decomposition increases with drop of ground water table level, enhancing N2O emission. An eight-year oil palm plantation study at a tropical peat land showed that NO3- N concentration decreased and N2O emissions decreased with the increase in oil palm yield. The yield of oil palm increased with the increase of water-filled pore space of the soil and N2O significantly decreased when the water-filled pore space became more than 70%. Therefore, following three managements are recommended to reduce N2O emission from agricultural soil: 1) Restrict excessive nitrogen application (apply nitrogen according to the amount of nitrogen taken up by crops); 2) Prevent excessive organic matter decomposition (maintain capillary water rise without excessively decreasing ground water table level in peatlands); 3) Prevent low pH of soil (apply compost to reduce chemical nitrogen fertilizer application).

Effects of organic manure partial substitution for chemical fertilizer on the photosynthetic rate, nitrogen use efficiency and yield of rice

Rational application of organic fertilizers is an effective approach to improve soil fertility, crop yield, and zero growth of chemical fertilizer in agricultural production. The rice variety 'Shennong9816' was planted in Shenyang, Liaoning Province, under seven different treatments: zero nitrogen fertilizer (CK), low nitrogen, 150 kg·hm-2(LN), medium nitrogen, 240 kg·hm-2 (MN), high nitrogen, 330 kg·hm-2(HN), medium nitrogen with replacement of chemical N by 10% organic manure (OMN10), medium nitrogen with replacement of chemical N by 20% organic manure (OMN20), and medium nitrogen with replacement of chemical N by 30% organic manure (OMN30). The effects of different treatments on photosynthetic rate, nitrogen absorption, nitrogen use efficiency, and yield were examined and the optimal fertilization scheme was determined. The results showed that the photosynthetic rate, biomass and yield were increased with the increases of nitrogen application rate, while the nitrogen use efficiency was decreased significantly. Compared with the MN treatment, the photosynthetic rate of OMN10 and OMN20 in filling stage was increased by 22.9% and 9.9%, respectively. The yield of OMN20 was increased by 3.8% compared to that of MN. The nitrogen agronomic efficiency and physiological efficiency of OMN20 were significantly improved by 8.1% and 13.3%, respectively. Moreover, the nitrogen agronomic efficiency and physiological efficiency of OMN20 were improved by 27.2% and 37.2% compared with the HN treatment. Thus, we concluded that the organic fertilizer replacement treatment could conserve soil fertility, achieve high yield and high nitrogen use efficiency, while reduce chemical nitrogen fertilizer application. The OMN20 treatment was recommended as a fertilizer application model due to its superior performance among the seven treatments.

Intercropping System and N2 Fixing Bacteria Can Increase Land Use Efficiency and Improve the Essential Oil Quantity and Quality of Sweet Basil (Ocimum basilicum L.).

Intercropping fodder plants with medicinal plants, in addition to enhancing productivity, can remarkably reduce the population of weeds, pests and diseases and for naturally meeting of livestock medicinal needs. Two experiments were conducted to evaluate biological yield, essential oil (EO) composition and yield of sweet basil (Ocimum basilicum L.) treated with N2 fixing bacteria in additive intercropping with forage maize during the 2018 and 2019. Treatments were arranged in factorial split-plot-in time in randomized complete block design with three replications. The factors were 100% chemical fertilizer (N), N2 fixing bacteria (Azospirillum brasilense and Azotobacter chroococcum), integration of N2 fixing bacteria + 50% nitrogen chemical fertilizer and control. The cropping pattern factor included of sole cropping basil and the additive intercropping of maize + 25% basil, maize + 50% basil, maize + 75% basil, and maize + 100% basil. The results indicated that the highest essential oil yield (30.8 kg ha−1) and essential oil percentage (0.75%) were obtained in sole cropping with A. brasilense and A. chroococcum + 50% chemical nitrogen fertilizer application in second harvest in 2019. In both cropping systems, the N2 fixing bacteria application significantly increased fresh and dry yield and land equivalent ratio (LER) as compared to control plants. In both years of experiments could remarkably vary depending on type of treatment. In both years, eight constituents including methyl chavicol (17.24–51.28%), Z-citral (neral) (8.33–24.3%), geranial (10.2–31.3%), (E)-caryophyllene (1.05–5.64%), α-trans-bergamotene (0.53–1.7%), α-humulene (0.4–1.69%), germacrene-D (0.2–1.88%), and (Z)-α- bisabolene (1.16–3.86%) were the main constituents of EO. The highest content of methyl chavicol was found through sole cropping of sweet basil with nitrogen chemical fertilizer followed by sole cropping of sweet basil with an integration of A. brasilense and A. chroococcum + 50% nitrogen chemical fertilizer in 2018 and 2019. Intercropping system and N2 fixing bacteria can be effective in reducing chemical fertilizer consumption and environmental pollution and achieving the sustainable agriculture goals.

Effects of long-term fertilization on soil microbial abundance in farmland of the Loess Plateau, China

Based on a long-term experiment in the Changwu Agro-ecological Experimental Station, the real-time PCR analysis was used to examine the soil microbial abundance and to reveal the effects on soil microbial community under different long-term fertilization systems. The results showed that compared to the CK (barren field), the population of bacteria increased by 21% and archaea by 32% in treatment with inorganic fertilizer application. The abundance of bacteria in the treatment of chemical fertilizer combined with organic fertilizer increased by 37% and archaea by 36%. The treatment with chemical fertilizer mixed with organic fertilizer significantly increased the abundance of bacteria and archaea. The soil AOB increased by 7.13 times while the soil AOA only by 0.2 folds after 30-year application of chemical nitrogen fertilizer. AOB was highly responsive to fertilizer application, especially to nitrogen fertilizer. Compared with the single nitrogen application and the application of nitrogen fertilizer mixed with organic fertilizer, phosphorus fertilizer significantly increased the abundance of nifH and pmoA. The content of nifH, nirS cd and pmoA in the abandoned land was significantly higher than that in the cultivated soil. Results from the correlation analysis on soil basic physical and chemical properties indicated that soil pH, total nitrogen and organic carbon were key factors affecting soil microbial community abundance. In conclusion, long-term fertilization significantly changed soil microbial abundance, and fertilization patterns and cultivating methods had significant effect on microbial community abundance.

Ecosystem services of partial organic substitution for chemical fertilizer in a peri-urban zone in China

Chemical nitrogen fertilizer application in the peri-urban zone has benefited food supply, but excess nitrogen input has altered multiple ecosystem services and caused an array of ecosystem dis-services that have degraded air and water quality. Using sewage sludge compost and pig manure to partially substitute chemical fertilizer nitrogen may promote sustainable ecosystem services. However, few studies have been conducted to evaluate the values of associate ecosystem services with a unified standard. To comprehensively understand the effect of partial organic substitution on ecosystem services (supporting vegetable production and sequestering soil organic carbon) and ecosystem dis-services (greenhouse gas emissions and reactive nitrogen release), we attempted to evaluate the ecosystem service from the perspective of economic assessment. A field experiment was conducted in a peri-urban zone in eastern China, including the following six treatments at equal total nitrogen application rates: (1) no fertilizer nitrogen applied; (2) 25% sewage sludge compost substitution; (3) 25% pig manure substitution; (4) 50% sewage sludge compost substitution; (5) 50% pig manure substitution and (6) chemical fertilizer nitrogen only. The results showed that partial organic substitution significantly increased annual vegetable yield by 27.8%–35.3% and annual soil organic carbon sequestration rate by 129.2%–213.8%. Moreover, greenhouse gas emissions (methane and nitrous oxide) were significantly decreased by 28.6%–43.2%; nitrogen leaching and runoff were significantly decreased by 39.0%–49.5% and 26.8%–62.0%, respectively; and ammonia volatilization was increased by 2.4%–27.8%. Overall, partial substitution with organic fertilizer decreased total reactive nitrogen losses by 19.9%–39.8% compared with the 100% chemical fertilizer nitrogen treatment. Although additional labor and higher input costs were required, partial organic substitution could obtain a higher net economic benefit of 25198–90670 ¥ ha−1 yr−1 compared with the sole application of chemical fertilizer nitrogen. The results suggest that partial substitution of chemical fertilizer with organic fertilizer can sustain ecosystem services and reduce ecosystem dis-services in the peri-urban zone and increase economic profits for farmers.

Winter cover crops alter methanotrophs community structure in a double-rice paddy soil

Methanotrophs play a vital role in the mitigation of methane emission from soils. However, the influences of cover crops incorporation on paddy soil methanotrophic community structure have not been fully understood. In this study, the impacts of two winter cover crops (Chinese milk vetch (Astragalus sinicus L.) and ryegrass (Lolium multiflorum Lam.), representing leguminous and non-leguminous cover crops, respectively) on community structure and abundance of methanotrophs were evaluated by using PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) and real-time PCR technology in a double-rice cropping system from South China. Four treatments were established in a completely randomized block design: 1) double-rice cropping without nitrogen fertilizer application, CK; 2) double-rice cropping with chemical nitrogen fertilizer application (200 kg ha–1 urea for entire double-rice season), CF; 3) Chinese milk vetch cropping followed by double-rice cultivation with Chinese milk vetch incorporation, MV; 4) ryegrass cropping followed by double-rice cultivation with ryegrass incorporation, RG. Results showed that cultivating Chinese milk vetch and ryegrass in fallow season decreased soil bulk density and increased rice yield in different extents by comparison with CK. Additionally, methanotrophic bacterial abundance and community structure changed significantly with rice growth. Methanotrophic bacterial pmoA gene copies in four treatments were higher during late-rice season (3.18×107 to 10.28×107 copies g–1 dry soil) by comparison with early-rice season (2.1×107 to 9.62×107 copies g–1 dry soil). Type I methanotrophs absolutely predominated during early-rice season. However, the advantage of type I methanotrophs kept narrowing during entire double-rice season and both types I and II methanotrophs dominated at later stage of late-rice.

Influence of long-term fertilization on the community structure and diversity of soybean rhizobia in black soil

The objectives of this study were to explore the effects of long-term fertilization on the community structure and diversity of soybean rhizobia in black soil. BOX-PCR, IGS-PCR-RFLP and 16S rDNA gene sequencing methods were used to analyze the genetic diversity of the 254 soybean rhizobia isolated from 7 treatments at Heilongjiang Long-term Fertilization Experiment Station. The 7 treatments were as follows: no fertilization (CK), organic manure (OM), chemical nitrogen (N1), double chemical nitrogen (N2), chemical nitrogen-phosphorus (N1P1), double chemical nitrogen-phosphorus (N2P2), chemical nitrogen plus organic manure (N1+OM). Soil properties were measured and analyzed to test for relationships with the community and diversity of soybean rhizobia. All of the tested rhizobia belonged to Bradyrhizobium, of which the majority were closely related to B. japonicum and the others closely to B. liaoningense. BOX-PCR fingerprints 第 1 期 关大伟等: 长期施肥对黑土大豆根瘤菌群体结构和多样性的影响 69 showed that the tested rhizobia could be divided into 15 groups at 70% similarity level. These groups clustered into 3 communities that correspond to no chemical fertilizer treatments (CK, OM), chemical nitrogen fertilizer treatments (N1, N2, N1+OM), and chemical nitrogen-phosphorus treatments (N1P1, N2P2), respectively. Canonical correspondence analysis showed that pH, available N, and available P of the soil were significantly correlated with the community of rhizobia (P=0.002, 0.004, 0.002, respectively). Soybean rhizobia diversity indices varied significantly among fertilization treatments. Shannon-Wiener and species richness index were highest in N2P2 and Simpson index was highest in the OM treatment. The species richness, Shannon-Wiener and Simpson index in N1 and N2 were significantly lower than those in other treatments. The results of path analysis showed that the pH and available P had the greatest direct positive effects on the 3 indices, and that available N indirectly affected the 3 indices through pH. In conclusion, long-term chemical fertilization results in changes to community structure of soybean rhizobia in black soil, and application of chemical nitrogen fertilizer by itself reduces the diversity of soybean rhizobia, while application of nitrogenphosphorus has the opposite effect.

The effect of nitrogen biofertilizer and nitrogen chemical fertilizer on yield and yield components of white bean (Phaseolus vulgaris,cv.Dorsa)

For evaluating the effects of bio and, chemical nitrogen fertilizer application on yield and yield components of white bean (Phaseolus vulgaris ,cv.Dorsa), a study was performed in the factorial form based on completely randomized block design with three replications ,during growing season of 2012-2013.Treatments were 3 levels of bio-fertilizer application as Nitro Kara (control, contaminated seed in planting stage and the full green stage) and 4 levels of chemical nitrogen fertilizer as urea (control, 100, 150 and 200 kg ha-1). Results of variance analyze showed that bio-fertilizer treatment had effected the No. pod/unit area, No. full pods/ unit area, No. empty pod/unit area, 100-grain weight and Seed yield. The mean comparison of data showed that the using biofertilizer as seed stained + 150kg urea/hectare increased the number of pods and full pods per unit of area an average 69% compared with the control. Also, the using bio-fertilizer as seed stained + 100kg urea/hectare increased the 100-grain weight and Seed yield an average 58% and 72% compared with the control, respectively. The using bio-fertilizer as seed stained + 150kg urea/hectare decreased the number of empty pods an average 2/66 times compared with the control.

Effects of seed inoculation by Rhizobium strains on yield and yield components in common bean cultivars (Phaseolus vulgaris L.)

To study the effect of Rhizobium inoculation treatments (inoculation with strains number 133, 116 and their integrated application) and chemical nitrogen fertilizer application (based on soil analysis in form of Urea) on certain agronomic traits of three common bean cultivars (viz. Bahman, Darkhshan and Sayyad) a field experiment was conducted at Agricultural Research Farm of College of Agriculture, University of Tehran (Karaj, Iran) during 2010 and 2011 growing seasons. The treatments arranged as factorial based on a randomized complete block design with three replications. The characteristics such as seed yield, pods number per plant, 100 seed weight, harvest index and biological yield were measured. Inoculated bean cultivars by rhizobium strain 116 produced the highest bean grain yield (5791 kg/ha). Bahman cv. inoculated by rhizobium strains 133+116 produced the highest number of pods per plant (55.97 pods/plant). Sayyad cultivar inoculated by rhizobium strain 116 produced the highest seed yield. Under the environmental conditions of this experiment, application of rhizobium strains proved to have the capability to replace the chemical nitrogen fertilizer in bean production.

Conservation tillage, local organic resources and nitrogen fertilizer combinations affect maize productivity, soil structure and nutrient balances in semi-arid Kenya

Smallholder land productivity in drylands can be increased by optimizing locally available resources through nutrient enhancement and water conservation. In this study, we investigated the effect of tillage system, organic resource, and chemical nitrogen fertilizer application on maize productivity in a sandy soil in eastern Kenya over four seasons. The objectives were to (1) determine effects of different tillage–organic resource combinations (tillage system and low quantities of organic resources) on soil structure and crop yield, (2) determine optimum organic–inorganic nutrient combinations for arid and semi-arid environments in Kenya, and (3) assess partial nutrient budgets of different soil, water, and nutrient management practices using nutrient inflows and outflows. This experiment, initiated in the short rainy season of 2005, was a split plot design involving tied ridges (under reduced tillage), no-till and conventional tillage, and organic resource (manure and/or crop residue) combinations in the main plots, and chemical nitrogen fertilizer in subplots. Although yield in no-till was lower than conventional and tied ridges during initial two seasons, it achieved higher yields than did the other tillage systems by season 4. Combined application of 1 t ha–1 of crop residue and 1 t ha–1 of manure increased maize yield over sole application of manure at 2 t ha–1 by between 17 and 51% depending on the tillage system for treatments without inorganic N fertilizer. Cumulative nutrients in harvested maize in the four seasons ranged from 57 to 190 kg N ha–1, 11 to 26 kg P ha–1, and 95 to 195 kg K ha–1, representing 23 and 62% of applied N in treatments with and without mineral fertilizer N, respectively, 10% of applied P, and 35% of applied K. There were higher total nutrient NPK uptake treatments under tied ridges than in those under no-till and conventional tillage systems. We conclude that even with modest organic resource application, conservation tillage can be effective in improving crop yield and soil structure and that farmers are better off applying 1 t ha–1 each of crop residue and manure rather than sole manure.

Effect of chemical nitrogen fertilizer application on the release of arsenic from sediment to groundwater in Bangladesh

The effect of chemical nitrogen fertilizer application on groundwater arsenic pollution was examined. Arsenic and N concentrations in peat sediment were high. In the groundwater, a high arsenic concentration was observed under a high ammonium-N concentration with reducing conditions. From _15N analysis, the source of N in peat sediment and groundwater was possibly chemical N fertilizer. Thus, we assumed that a high N environment created by the fertilizer led the groundwater to reducing conditions through the enhancement of microbial activity, and the reducing condition promoted the arsenic release from peat sediment to the groundwater.