Nitrogen, Volume 2, Issue 3 (September 2021) – 7 articles

Economic use of organic and inorganic fertilizers following their availability is necessary for livestock-based Nepalese farming systems. However, how best to integrate these fertilizers in an appropriate manner is not yet clear. Thus, this study was conducted in the horticulture farm of the Agriculture and Forestry University (AFU), Rampur, Chitwan, Nepal from November 2018 to February 2019 to evaluate the effect of organic and inorganic sources of nitrogen (N) on growth, yield, and quality of beetroot (Beta vulgaris L.) varieties. The experiment was laid out in a two factorial randomized complete block design with four replications consisting of two beetroot varieties, i.e., Madhur and Ruby Red, and five N source combinations, i.e., N₁: 100% poultry manure (PM), N₂: 50% PM + 50% urea, N₃: 100% farmyard manure (FYM), N₄: 50% FYM + 50% urea, and N₅: 100% urea (120:80:40 kg NPK ha⁻¹). Results of this study indicated a significant impact of N sources and varieties on the assessed parameters. During harvest, a significantly higher plant height (41.84 cm), number of leaves per plant (14.68), leaf length (34.56 cm), leaf width (11.38 cm), and beetroot diameter (72.15 mm) were observed in the N₂ treatment. Likewise, higher economic (49.78 t ha⁻¹) and biological yields (78.69 t ha⁻¹) were also recorded in the N₂ compared to other N sources. Out of the two varieties, the Madhur variety was significantly better in most growth and yield parameters. Similarly, the Madhur variety showed a significantly higher economic (44.49 t ha⁻¹) and biological yields (69.79 t ha⁻¹) compared to the Ruby Red variety. However, the physiological weight loss was higher in the Ruby Red variety. Therefore, the current study suggests that an integration of poultry manure along with the combination of N fertilizer and the Madhur variety is the best combination for quality beetroot production in the Terai region of Nepal. Full article

The optimum dose of fertilizers for crops varies with soil, agro-ecology, and crop management practices. Optimizing application dose is critical to reduce nutrient loss to the environment and increase nitrogen use efficiency (NUE), crop yields, and economic return to farmers. An experiment was conducted to determine the optimum N dose for increasing maize (Zea mays L. cv, Manakamana-3) yield, NUE, and farm profits under rainfed conditions. Five levels of N (0, 60, 120, 180, and 240 kg ha⁻¹), and a non-fertilized treatment were tested in a randomized complete block design with three replications. Effects of each treatment on yield and yield attributing traits, plant lodging and Sterility (plants with no cob or grain formation), NUE, and stay green trait of maize were recorded. Application of N above 120 kg ha⁻¹ (N120) did not have any significant effects on yield and yield components. Nitrogen, at N120 and above, produced highly fertile plants (though sterility slightly increased at N180 and N240), higher N uptake, and lower dead leaf area (18–27%). N120 produced the highest agronomic; yield increase per unit of N application (AEN—26.89 kg grain kg⁻¹ N) and physiological efficiency of N (PEN—42.67 kg grain kg⁻¹ N uptake), and net benefit (USD 500.43). Considering agronomic, economic, and NUE factors, an N dose of 120 kg ha⁻¹ was found optimum for the cultivation of rainfed maize (Manakamana-3) under sandy loam soil. Full article

Manure is a common source of nitrogen (N) in organic farming. However, manure is not always easily available, while the maximum N amount added as animal manure in organic agriculture is restricted by EU regulations. The present study was designed to test whether green manuring with a warm-season legume and intercropping with a cold-season legume can substitute farm-yard manure or compost as N sources in organic greenhouse tomato crops. To test this hypothesis, a winter-spring (WS) tomato crop was installed in February following the incorporation of crop residues of an autumn-winter (AW) tomato crop intercropped with faba bean, which had been fertilized with cowpea residues as green manure. This treatment, henceforth termed legume treatment (LT), was compared with the use of compost or manure as an N fertilization source in both tomato crops. In addition, a combination of compost and LT was also used as a fourth treatment. The results showed that green manuring with legumes and particularly cowpea can contribute a significant amount of N to the following organic tomato crop, through the biological fixation process. Nevertheless, legumes as green manure, or compost, or their combination cannot efficiently replace farmyard manure as an N fertilization source. Compost exhibited a slow mineralization course. Full article

South African soils generally lack native Bradyrhizobium strains that nodulate and fix atmospheric nitrogen (N₂) in soybeans (Glycine max L.). It is therefore very important to inoculate soybeans with products that contain effective Bradyrhizobium strains as active ingredients. In this study, a field experiment was conducted on two bioclimatic zones in South Africa during the 2019/2020 season to assess the effect of Bradyrhizobium japonicum strain WB74 inoculant formulation on nitrogen fixation, growth and yield improvement in soybeans. The first bioclimatic zone was characterized by a sandy clay loam soil, whereas the second bioclimatic zone has a sandy loam soil. The results showed that inoculation of soybeans with both peat and liquid formulations of Bradyrhizobium japonicum WB74 increased nitrogen uptake, which resulted in yield increase. The amount of N fixed was measured as ¹⁵N isotopes and increased with all treatments compared to the uninoculated control in both liquid and peat inoculant formulations. In bioclimatic zone A, slightly better results were obtained using the liquid formulation (1.79 t ha⁻¹ for liquid compared to 1.75 t ha⁻¹ for peat treatments), while peat formulations performed better in bioclimatic zone B (1.75 t ha⁻¹ for peat compared to 1.71 t ha⁻¹ for liquid treatments). In both areas higher yields were obtained with the formulations used in this study compared to the registered standards (treatment T3). The findings in this study provide vital information in the development and application of formulated microbial inoculants for sustainable agriculture in South Africa. Full article

Synthetic nitrogen fertilizer use comes with unsustainable financial and environmental costs, making it not attractive to small-scale and organic farmers. Poultry manure (PM) when available is a primary fertilizer source for small-scale and organic farmers but there is still limited research on its effects of specific crops and soil fertility under specific practices. The study investigated PM effects on garden egg in three seasons in Ghana and PM effects soil fertility in sandy-loam soils of Arizona after three years under flood irrigation and no-till. The PM application improved garden egg growth (dry matter by 73%) and increased yield by 66% in slightly acidic sandy-loam tropical soils, which could be related to soil mineral improvement. In the semi-arid soil, three years PM application increased cation exchange capacity (41%), P (471%), K (18%), S (244%), Ca (45%), Mg (31%), Zn (5%) and Mn (19%) with reduction in nitrate (−26%), Fe (−38%) and Cu (−11%). The reduction in the nitrate and Fe in the semi-arid Arizona cropland could be associated to flood irrigation and high soil pH, respectively. To gain the full potential from PM applications, best management practice is recommended to reduce nitrate leaching. Full article

Environmental pollution is a major threat to public health and is the cause of important economic losses worldwide. Atmospheric nitrogen deposition is one of the most significant components of environmental pollution, which, in addition to being a health risk, is one of the leading drivers of global biodiversity loss. However, monitoring pollution is not possible in many regions of the world because the instrumentation, deployment, operation, and maintenance of automated systems is onerous. An affordable alternative is the use of biomonitors, naturally occurring or transplanted organisms that respond to environmental pollution with a consistent and measurable ecophysiological response. This policy brief advocates for the use of biomonitors of atmospheric nitrogen deposition. Descriptions of the biological and monitoring particularities of commonly utilized biomonitor lichens, bryophytes, vascular epiphytes, herbs, and woody plants, are followed by a discussion of the principal ecophysiological parameters that have been shown to respond to the different nitrogen emissions and their rate of deposition. Full article

Nitrogen fertilizer recommendations for corn (Zea mays L.) should ensure high yields using adequate N doses. Soil–plant analysis development (SPAD) meter technology using absolute SPAD values, might be more reliable than relative SPAD values in helping corn producers making timely decisions about N applications. This study aimed to develop a relationship between absolute SPAD values and leaf N concentration, and to determine optimal leaf N concentrations at early corn growth stages (V6, V8, V10, and V12). Three experiments were conducted during two summer seasons (2014 and 2015) using six N treatments applied at early corn growth stages. In parallel, two experiments were carried out in a high residual N environment to establish the optimum corn leaf N concentration. Results showed a significant linear relationship between corn leaf N concentrations and absolute SPAD values (R² = 0.80, p < 0.05). The mean optimum corn leaf N concentration decreased over corn growth stages. It is of great importance to make the absolute SPAD method accessible for farmers, but more research is required to perform standardized reading of absolute SPAD values data. Full article