The effect of dicyandiamide and neem cake on the nitrification of urea-derived ammonium under field conditions

Summary Dicyandiamide (DCD) and neem cake were evaluated for their efficiency in inhibiting nitrification of prilled urea-derived NH ₄ ⁺ –N in a wheat field. Prilled urea was blended with 10% and 20% DCD-N or 10% and 20% neem cake and incorporated into the soil just before the wheat was sown. Both DCD and neem cake partially inhibited nitrification of prilled urea-derived NH ₄ ⁺ ; DCD was better than neem cake. The nitrification-inhibiting effects of DCD lasted for 45 days, while that of neem cake lasted for only 30 days. Blending the prilled urea with DCD (20% on N basis) was most effective in inhibiting the nitrification of urea-derived NH ₄ ⁺ , both in terms of intensity and duration, and maintained substantially more NH ₄ ⁺ –N than the prilled urea alone and 20% neem-cake-blended urea for a period of 60 days.     

Dicyandiamide (DCD) as a nitrification inhibitor for rice culture in the United States

Abstract

Efficient nitrogen (N) fertilizer management for paddy rice production is difficult because of potentially high N losses from denitrification, NH₃ volatilization, and leaching. The use of a nitrification inhibitor, by slowing the rate of nitrification of NH₄ ⁺‐N sources prior to flooding, offers the potential to reduce denitrification losses that occur after flooding. Dicyandiamide (DCD) is one such nitrification inhibitor. The objective of this series of studies was to evaluate DCD for its effectiveness as a nitrification inhibitor in paddy rice production across an array of soils, management systems, and climate conditions.

Studies were conducted on fine‐ and medium‐textured soils in Arkansas, California, Louisiana, Mississippi, and Texas. Dicyandiamide was coated onto or formulated with urea (7 or 10% of total N as DCD‐N) and applied either broadcast pre‐plant incorporated or broadcast as a topdress application prior to flooding at the 4‐ to 5‐leaf development stage of the rice plant. These treatments were compared with urea applied either pre‐plant incorporated or in multiple applications timed to the peak N demand periods of rice. An array of N rates were used to model the yield response to levels of N. Similar studies utilizing ¹⁵N‐enriched urea were also conducted.

The studies indicated that use of DCD delayed nitrification and tended to result in rice grain yield increases as compared with urea applied pre‐plant without DCD in drill‐seeded rice; however, proper application of urea in split applications gave more consistent results. In water‐seeded continuously flooded rice culture, use of DCD was advantageous only if the flood was delayed for more than 14 days after urea application. The ¹⁵N‐enriched studies indicated that highest N fertilizer recovery was associated with split topdress urea applications; however, addition of DCD resulted in increased immobilization of fertilizer N and release of soil N.     

Laboratory evaluation of dicyandiamide as a soil nitrification inhibitor

Abstract

Laboratory studies to evaluate dicyandiamide (DCD) as a soil nitrification inhibitor showed that it is considerably more effective than several compounds that have been patented or proposed as fertilizer amendments for retarding nitrification of fertilizer nitrogen (N) in soil, but is considerably less effective than 2‐ethynylpyridine, nitrapyrin (N‐Serve), etridiazole (Dwell), 3‐methylpyrazole‐l‐carboxamide (MPC), or 4‐amino‐l,2,4‐triazole (ATC). Other findings in studies reported were as follows: a) DCD is more effective for inhibiting nitrification of ammonium‐N than of urea‐N; b) the effectiveness of DCD as a nitrification inhibitor is markedly affected by soil temperature and soil type and is limited by the susceptibility of DCD to leaching; c) DCD has very little, if any, effect on urea hydrolysis, denitrification, or seed germination in soil; d) products of DCD decomposition in soil (guanylurea and guanidine) have little, if any, effect on nitrification compared with DCD; e) in the absence of leaching, the persistence of the inhibitory effect of DCD on nitrification decreases with increase in soil temperature from 10 to 30°C, but the inhibitory effect of 50 μg DCD g^‐1 soil is substantial even after incubation of DCD‐treated soils at 20 or 30°C for 24 weeks.     

Influence of physicochemical parameters of neem (Azadirachta indica A Juss) oils on nitrification inhibition in soil

The technology for the production of neem oil coated urea (NOCU) developed by the Indian Agricultural Research Institute is in the pipeline for adaption by several Indian fertilizer industries. Use of nitrification inhibitors is one of the methods of improving the nitrogen use efficiency (NUE) of nitrogenous fertilizers in agriculture. However, standard specifications for the neem oil as a raw material of NOCU are desired. Accordingly, the present study was undertaken to evaluate 25 samples of neem oils comprising 11 samples of expeller grade (EG) oils, 8 samples of cold-pressed (CP) oils, 3 samples of solvent-extracted oils, and 2 commercial formulations. NOCU was prepared using these oils (5000 ppm of urea-N). The soils fertilized with NOCUs (200 ppm of urea-N) were incubated at 27 degrees C and 50% water-holding capacity for a period of 15 days. Nitrapyrin (0.5% of N) coated urea served as the reference and prilled urea as control. Samples were analyzed for NH4+-N, NO2--N, and NO3--N using standard methods. The percent nitrification inhibition (NI) was calculated, and the results revealed that all of the neem oils caused NI ranging from 4.0 to 30.9%. Two samples of EG oils and two commercial formulations were found to be the best, causing 27.0-30.9% NI. Iodine, acid, and saponification values and meliacin content of all of the oils were analyzed and correlated with NI. The results revealed the direct influence of meliacin content of the neem oils on NI, which, however, was found to be negatively correlated with saponification and iodine values. There is, therefore, a need to introduce new Bureau of Indian Standards (BIS) specifications for neem oils as raw materials of NOCU.     

Effectiveness of dicyandiamide as a nitrification inhibitor in biochar-amended soil

Overuse of nitrogen (N) fertilizers may lead to many environmental issues via N leaching into groundwater and agricultural runoff into surface water. Biochar, a sustainable soil amendment agent, has been widely studied because of its potential to retain moisture and nutrients. However, recent studies have shown that biochar has a very limited ability to improve the retention of negatively charged nitrite (NO₂^-) or nitrate (NO₃^-). Although positively charged ammonium (NH₄⁺) can be better held by biochar, it is usually susceptible to nitrification and can be easily transformed into highly mobile NO₂^-and/or NO₃^-. In practice, dicyandiamide (DCD) has been used to inhibit nitrification, preserving N in its relatively immobile form as NH₄⁺. Therefore, it is likely that the effects of DCD and biochar in soils would be synergistic. In this study, the influences of biochar on the effectiveness of DCD as a nitrification inhibitor in a biochar-amended soil were investigated by combining the experimental results of incubation, adsorption isotherm, and column transport with the simulated results of different mathematical models. Biochar was found to stimulate the degradation of DCD, as the maximum degradation rate slightly increased from 1.237 to 1.276 mg kg^-1 d^-1 but the half-saturation coefficient significantly increased from 5.766 to 9.834 mg kg^-1. Considering the fact that the availability of DCD for nitrification inhibition was continuously decreasing because of its degradation, a novel model assuming non-competitive inhibition was developed to simulate nitrification in the presence of a decreasing amount of DCD. Depending on the environmental conditions, if the degradation of DCD and NH₄⁺ in biochar-amended soil is not significant, improved contact due to the mitigated spatial separation between NH₄⁺ and DCD could possibly enhance the effectiveness of DCD.     

Research on dicyandiamide as a nitrification inhibitor and future outlook

Abstract

The action and decomposition of dicyandiamide (DCD), a nitrification inhibitor, is discussed.

DCD is especially efficient when used with animal manure slurries or potato starch waste water. As a consequence, nitrate leaching can be reduced, yields and N uptake increased. DCD‐amended mineral N fertilizers applied once can substitute for split N applications, thus reducing labor costs without any loss in crop yield and quality. With wheat and sugar beets, use of a DCD‐containing product ("Alzon 22") reduced the requirement of N for maximum yield. New formulations, such as DCD plus a reducing substance, ammonium thiosulfate (ATS), or new inhibitors, such as guanylthiourea (GTU), will receive more attention in the future.     

Comparative analysis of seed morphometric and allozyme data among four populations of neem (Azadirachta indica)

The objectives of this study were to determine the patterns of variability and to compare genetic distance between seed morphometric and allozyme data of neem (Azadirachta indica). Phenotypic variation from open pollinated seed materials at 12 isozyme loci was examined using starch gel electrophoresis for four populations from Thailand, Bangladesh and Kenya. All four populations exhibited high levels of variation for seed parameters and isozymes. UPGMA cluster analysis of Nei's genetic distance when based on isozymes revealed two genetic groups. The population from Kenya showed a close genetic relationship with the Bangladeshi populations. The population from Thailand exhibited a distant relationship with the other three populations. This result suggests that the Kenyan population was introduced from the Indian subcontinent. In contrast, cluster analysis of seed morphometric data indicated three different groups of populations. The population from Kenya showed a distant relationship with all other populations. The study demonstrates that allozyme data may not correspond with morphometric traits when measuring genetic distance. It is suggested that this controversy may depend on environmental influence on morphometric traits, possibly also on the enzyme patterns.     

Evaluation of 3-methylpyrazole-1-carboxamide as a soil nitrification inhibitor

Summary Laboratory studies to evaluate 3-methylpyrazole-1-carboxamide (MPC) as a soil nitrification inhibitor showed that it was comparable to nitrapyrin (N-Serve) for inhibiting nitrification of ammonium in soil, but was not as effective as etridiazole (Dwell) or 2-ethynylpyridine. They also showed that the effectiveness of MPC as a soil nitrification inhibitor is markedly affected by soil type and soil temperature, that MPC is more effective for inhibiting nitrification of ammonium-N than of urea-N, and that MPC has little, if any, effect on hydrolysis of urea or denitrification of nitrate in soil. These observations and other work discussed indicate that MPC is one of the most promising compounds so far proposed for inhibition of nitrification in soil.     

A novel amended nitrification inhibitor confers an enhanced suppression role in the nitrification of ammonium in soil

Journal of Soils and Sediments - Nitrification inhibitor plays an important regulatory role in inhibiting the nitrification of ammonium in soils. However, most of nitrification inhibitors lack the...     

Dicyandiamide as a nitrification inhibitor in crop production in the Southeastern USA

Abstract

The yield response to N with and without the use of the nitrification inhibitor, dicyandiamide (DCD), was determined on the field crops, sweet corn, cotton, wheat, and grain sorghum; and on the vegetable crops, bell peppers, potato, and tomato, on a large number of different soils in Alabama, Florida, Kentucky, Mississippi, and Virginia. In general, DCD inhibited nitrification for several weeks but inhibiting nitrate formation was not often reflected in crop yield response to N. Increase in yield resulting from DCD use were found for sweet corn in Florida, grain sorghum in Alabama, and potato in one of two years in Florida. Results with cotton were erratic, sometimes resulting in increased, sometimes in decreased, yields. Use of DCD for wheat production in the Southeast did not prove to be advantageous. Generally when DCD use benefitted yields, this occurred at the lower N rates, indicating that preventing loss of N at the lower end of the response curve resulted in a measurable positive effect. The studies reported indicate that consistent benefit from DCD use in the southeastern United States is unlikely.     

3,4-Dimethylpyrazole phosphate (DMPP) – a new nitrification inhibitor for agriculture and horticulture

3,4-Dimethylpyrazole phosphate (DMPP) is a new nitrification inhibitor with highly favourable properties. It has undergone thorough toxicology and ecotoxicology tests and application-technology experiments, and has been shown to have several distinct advantages compared to the currently used nitrification inhibitors. Application rates of 0.5-1.5 kg ha^-1 are sufficient to achieve optimal nitrification inhibition. DMPP can significantly reduce NO₃^- leaching, without being liable to leaching itself. DMPP may reduce N₂O emission, apparently without a negative effect on CH₄ oxidation of the soil. The use of DMPP-containing fertilizers can improve yield. This offers the possibility of saving mineral fertilizer N, reducing the number of N-application rounds, and obtaining higher crop yields with current fertilizer-N rates.     

A bioassay to determine the effect of organic matter and pH on the effectiveness of nitrapyrin (N-Serve) as a nitrification inhibitor

The aerobic incubation procedures commonly used in biological studies have several disadvantages to assess inhibition of nitrification. Therefore, a more suitable procedure was developed. It involves pre-incubating soil samples treated with (NH₄)₂HPO₄ to establish a uniform population of nitrifiers before the addition of the nitrification inhibitor or other amendments. Through successive additions of (NH₄)₂HPO₄, a constant nitrification rate is maintained. This system enables direct comparison between treatments throughout the experiment.Data obtained using this procedure indicated that sorption of Nitrapyrin (NI) is a major factor decreasing the effectiveness of NI in organic soils. Loss of NI by volatilization also decreased its effectiveness, while the relative inhibition by NI was found to increase as soil pH increases. The greater susceptibility of nitrifiers to NI at high pH may be due to a relationship between pH and nitrifier ecology.     

Influence of soil parameters on the effect of 3,4-dimethylpyrazole-phosphate as a nitrification inhibitor

Nitrification inhibitors specifically retard the oxidation of NH₄⁺ to NO₂^- during the nitrification process in soil. In this study, the influence of soil properties on the nitrification-inhibiting effect of 3,4-dimethylpyrazole-phosphate (DMPP), a newly developed nitrification inhibitor, has been investigated. Based on short-term incubation experiments, where the degradation of DMPP could be largely disregarded, the oxidation of the applied NH₄⁺ was more inhibited in sandy soils compared with loamy soils. The influence of soil parameters on the relative NO₂^- formation could be described by a multiple regression model including the sand fraction, soil H⁺ concentration and soil catalase activity (R²=0.62). Adsorption studies showed that the binding behaviour of DMPP was influenced markedly by soil textural properties, viz. the clay fraction (r²=0.61). The adsorption of DMPP was found to be an important factor for the inhibitory effect on NH₄⁺ oxidation in a short-term incubation (r²=0.57). It is concluded that the evaluated soil properties can be used to predict the short-term inhibitory effect of DMPP in different soils. The significance of these results for long-term experiments under laboratory and field conditions needs further investigation.     

Correction of iron chlorosis in peanut (arachis hypogea shulamit) by ammonium sulfate and nitrification inhibitor

Peanut (Arachis hypogea cv. Shulamit) grown on very high calcium carbonate (CaCO₃) content soils is showing iron (Fe) chlorosis symptoms. Supplying the plant with ammonium sulphate ((NH₄)₂SO₄) in the presence of nitrapyrin (N‐Serv) for preventing nitrification reduced Fe chlorosis. Nitrate (NO^‐ ₃) developed in the soil with time, even with nitrapyrin present. When ammonium (NH⁺ ₄) was even less than 20% of the total mineral N in the soil, no Fe‐stress could be observed, suggesting that the NH⁺ ₄ uptake by the plant and the consequence of hydrogen (H⁺) efflux occurs from the root to the rhizosphere, resulting in a decrease of redox potential near the root, and solubilizing enough Fe near the root to overcome the chlorosis.     

Balance and immobilization of (15NH4)2SO4 in a soil after the addition of Didin as a nitrification inhibitor

Summary We studied the effect of a dicyandiamide-based nitrification inhibitor (Didin) on the kinetics of N transfer in soil. Incubation at various temperatures was carried out in the laboratory after adding ammonium sulfate labelled with ¹⁵N. Adding Didin increased the incorporation of mineral N in a form that could not be extracted by KCl. The temperature modified the incorporation kinetics, but after 1 year, no difference remained between the two treatments in which the inhibitor had been added, and in which the total N immobilized was 26% of the ¹⁵N added compared with 13% in the control treatment. Losses of ¹⁵N, measured by difference, were greater in the control treatment (approximately 14%) than in the treatments containing Didin (10%). The addition of a nitrification inhibitor did not lead to the development of denitrifying microflora, the losses being mainly attributable to volatilization of NH₃ encouraged by the high pH of the soil. The immobilized N was mainly found in the NH₄ ⁺ form, adsorbed at the beginning of the incubation and subsequently in the amino acids. It seemed that the Didin effect on microflora was indirect, arising from longer maintenance of the tracer in NH₄ ⁺ form. This hypothesis was borne out by computing the gross phenomena. The variation in results reported in the literature can therefore be attributed to modifications in immobilization kinetics.     

乙醇浸提紫苏籽压榨饼中油脂的工艺

为探讨乙醇作为植物油浸提溶剂的可行性,对乙醇溶液浸提紫苏籽低温压榨饼的工艺进行了研究。在浸提温度78℃下,采用单因素试验考察了浸提次数、料液比、乙醇浓度等因素对浸提粕中的残油率、蛋白质、单宁及植酸含量的影响。通过正交试验获得优化的工艺条件为:浸提次数为6次,料液比1︰2.5,乙醇浓度90%。在该工艺条件下,所获得的紫苏浸提粕中残油率为0.46%,蛋白质含量为50.5%(N×6.25,干基),单宁含量为1.7%,植酸含量为6.01%。当浸提所获混合油中油含量超过1%时,将混合油冷却至5℃下24h可观察到分相现象,其中轻相含油量在3%以下,重相含油量在90%以上,有利于溶剂回收。因此,将乙醇溶液作为植物油脂浸提溶剂有很大的潜力,但还需开展进一步的研究以推进该溶剂的工业应用。     

Influence of temperature on mineralization kinetics with a nitrification inhibitor (mixture of dicyandiamide and ammonium thiosulphate)

Summary The influence of temperature on the action of a dicyandiamide nitrification inhibitor was studied during a laboratory incubation after the addition of ammonium sulphate labelled with ¹⁵N. In the control treatment, nitrification was only slightly affected by temperature and was rapid; on the 42nd day, two-thirds of the ¹⁵N was incorporated into the nitrate fraction while no further tracer was found in ammoniacal form. With the addition of dicyandiamide, the process was slowed down considerably when the temperature was maintained at 10°C, and only about 10% of the ¹⁵N was nitrified in 6 months. After 1 month of incubation at 10°C, a temperature increase to 15°C for 4 weeks modified the nitrification kinetics only slightly. However, as soon as the temperature reached 20°C, the beginning of dicyandiamide decomposition and an increase in the quantity of NO ₃ ^- -N was observed. The inhibition was measured by the nitrification index, which was greater than 80% as long as the temperature did not exceed 15°C, and decreased to 10% after 6 months; this value was reached only after 1 year in soil maintained at 10°C. The half-life of the NH ₄ ⁺ was decreased by raising the temperature. In the experimental conditions described, nitrification was inhibited by the dicyandiamide for at least 6 months provided the temperature did not exceed 15°C.     

Extraction and colorimetric determination of azadirachtin-related limonoids in neem seed kernel.

A colorimetric method was developed for the determination of total azadirachtin-related limonoids (AZRL) in neem seed kernel extracts. The method employed acidified vanillin solution in methanol for the colorization of the standard azadirachtin or neem seed kernel extracts in dichloromethane. Through the investigation of various factors influencing the sensitivity of detection, such as the concentration of vanillin, acid, and the time required for the formation of color, optimum conditions were selected to perform the assay. Under the optimum conditions, a good linearity was found between the absorbance at 577 nm and the concentration of standard azadirachtin solution in the range of 0.01-0.10 mg/mL. In addition, different extraction procedures were evaluated using the vanillin assay. The HPLC analysis of the extracts indicated that if the extractions were performed in methanol followed by partitioning in dichloromethane, approximately 50% of the value determined by the vanillin assay represents azadirachtin content.     

Nitrous oxide emissions from animal urine as affected by season and a nitrification inhibitor dicyandiamide

Purpose  

Nitrous oxide emissions from pasture soils account for one third of total agricultural greenhouse gas emissions in New Zealand. The aim of this study was to determine nitrous oxide (N₂O) emissions from animal urine patches under summer (with irrigation) and winter conditions as affected by dicyandiamide (DCD) in grazed grassland in New Zealand.