Climate Overrides Effects of Fertilizer and Straw Management as Controls of Nitrous Oxide Emissions After Oilseed Rape Harvest

Oilseed rape (Brassica napus L.) is an important bioenergy crop that contributes to the diversification of renewable energy supply and mitigation of fossil fuel CO2 emissions. Typical oilseed rape crop management includes the use of nitrogen (N) fertilizer and the incorporation of oilseed rape straw into soil after harvest. However, both management options risk increasing soil emissions of nitrous oxide (N2O). The aim of this 2-years field experiment was to identify the regulating factors of N cycling with emphasis on N2O emissions during the post-harvest period. As well as the N2O emission rates, soil ammonia (NH4+) and nitrate (NO3−) contents, crop residue and seed yield were also measured. Treatments included variation of fertilizer (non-fertilized, 90 and 180 kg N ha−1) and residue management (straw remaining, straw removal). Measured N2O emission data showed large intra- and inter-annual variations ranging from 0.5 (No-fert + str) to 1.0 kg N2O-N ha−1 (Fert-180 + str) in 2013 and from 4.1 (Fert-90 + str) to 7.3 kg N2O-N ha−1 (No-fert + str) in 2014. Cumulative N2O emissions showed that straw incorporation led to no difference or slightly reduced N2O emissions compared with treatments with straw removal, while N fertilization has no effect on post-harvest N2O emissions. A process-based model, CoupModel, was used to explain the large annual variation of N2O after calibration with measured environmental data. Both modeled and measured data suggest that soil water-filled pore space and temperature were the key factors controlling post-harvest N2O emissions, even though the model seemed to show a higher N2O response to the N fertilizer levels than our measured data. We conclude that straw incorporation in oilseed rape cropping is environmentally beneficial for mitigating N2O losses. The revealed importance of climate in regulating the emissions implies the value of multi-year measurements. Future studies should focus on new management practices to mitigate detrimental effects caused by global warming, for example by using cover crops.

Application of Corn Straw and Woody Peat to Improve the Absorption and Utilization of 15N-Urea by Maize

Increasing nitrogen fertilizer use efficiency has become an environmental and economic demand in order to minimize losses of nitrogen and maximize the output from nitrogen added. The application of organic amendments with N fertilizers could be proposed as an important economic and environmental practice for improving N fertilizer use. A two-year field experiment was carried out using the 15N tracer technique to study the impact of corn straw and woody peat application on uptake and utilization of N fertilizer by maize plant. Three treatments were set up: CK (15N labeled urea alone), CS (15N labeled urea + crushed corn straw) and WP (15N labeled urea+ crushed woody peat). The results showed that, as compared to CK, both straw and peat treatments led to (i) an increase in yield of maize, 15N urea utilization rate, and residual 15N urea remained in soil by 11.20% and 19.47%, 18.62% and 58.99%, 41.77% and 59.45%, respectively, but (ii) a decrease in the total loss rate by 6.21% and 16.83% (p < 0.05), respectively over the two seasons. Moreover, the significantly highest effect was recorded with woody peat application rather than that with corn straw. Our study suggests that corn straw and woody peat can be used as organic fertilizers to increase maize yields, promote nitrogen fertilizer balance sheet, reduce the leaching of N fertilizer into the subsurface soil layer, and facilitate the further absorption and utilization of soil residual nitrogen. Therefore, the application of humified organic material play a crucial role in N utilization efficiency enhancement.

Effect of P fertilizer and precipitation on wheat under permanent beds in the absence of N fertilizer application

Environmental conditions contribute to a large percentage of wheat yield variability. This phenomenon is particularly true in rainfed environments and non-responsive soils to N. However, the effect of P application on wheat is unknown in the absence of N fertilizer application. This study was conducted from 2012 to 2019 in permanent beds established in 2005. Treatments were arranged in a split-plot design and consisted of superimposing three P treatments (foliar, banded and broadcast application) plus a check (0P) within each one of four preceding N treatments (applied from 2005 to 2009). Foliar P generally showed a greater response than granular P treatments even though the soil tests high P (>30 mg/kg). Precipitation estimated for two different growth intervals explained through regression procedures the Years' effect. Seasonal precipitation (224–407 mm) explained variation of relative yield, N harvest index (NHI) and P agronomic efficiency (AE). Reproductive stage precipitation (48–210 mm) explained soil N supply. In dry years, foliar P application improved predicted relative yield 14% and AE 155 kg grain/kg P compared to granular P treatments. Similarly, soil N supply increased 15 kg/ha in dry moisture conditions during the reproductive stage. The NHI consistently improved over the crop seasons. This improvement was relatively larger for 0 kg N/ha. On average, NHI increased from about 0.57 to 0.72%. Normalized difference vegetation index (NDVI) readings at the booting growth stage were negatively associated with NHI. Foliar P in this non-responsive soil to N showed the potential to replace granular P sources. However, the omission of granular P needs to be further studied to estimate the long-term effect on the soil P test.

Effect of 50 Years of No-Tillage, Stubble Retention, and Nitrogen Fertilization on Soil Respiration, Easily Extractable Glomalin, and Nitrogen Mineralization

In subtropical regions, we have an incomplete understanding of how long-term tillage, stubble, and nitrogen (N) fertilizer management affects soil biological functioning. We examined a subtropical site managed for 50 years using varying tillage (conventional till (CT) and no-till (NT)), stubble management (stubble burning (SB) and stubble retention (SR)), and N fertilization (0 (N0), 30 (N30), and 90 (N90) kg ha−1 y−1) to assess their impact on soil microbial respiration, easily extractable glomalin-related soil protein (EEGRSP), and N mineralization. A significant three-way tillage × stubble × N fertilizer interaction was observed for soil respiration, with NT+SB+N0 treatments generally releasing the highest amounts of CO2 over the incubation period (1135 mg/kg), and NT+SR+N0 treatments releasing the lowest (528 mg/kg). In contrast, a significant stubble × N interaction was observed for both EEGRSP and N mineralization, with the highest concentrations of both EEGRSP (2.66 ± 0.86 g kg−1) and N mineralization (30.7 mg/kg) observed in SR+N90 treatments. Furthermore, N mineralization was also positively correlated with EEGRSP (R2 = 0.76, p < 0.001), indicating that EEGRSP can potentially be used as an index of soil N availability. Overall, this study has shown that SR and N fertilization have a positive impact on soil biological functioning.

Uptake and assimilation of nutrient resources.

Fruit trees require six macronutrients (N, P, K, calcium, Mg and sulfur) and eight micronutrients (Zn, Fe, B, Mn, Cu, chlorine, nickel and molybdenum) that are taken up through the roots. Many of these occur naturally in the soil as cations bound to negatively charged soil particles, while others are dissolved in the liquid surrounding the soil particles in the form of anions. This chapter discusses the uptake and assimilation of nutrient resources in fruit trees. Tabulated data are given on mean annual N, P and K storage (kg/ha) in perennial organs of mature almond trees that received N fertilizer at 309 kg/ha.

Assessment of Reactive Nitrogen Flows in Bangladesh’s Agriculture Sector

To assess the status of and trends in agricultural nitrogen (N) flows and their wider consequences for Bangladesh, in this study, we analyzed data from national and international bodies. The increased rates of N fertilizer applied for increased food production leaves behind a huge amount of unutilized reactive N (Nr). N fertilizer use is the largest in the crop sector, an important sector, where current annual consumption is 1190 Gg. The present combined annual Nr production from crop, fishery, and livestock sectors is ~600 Gg, while emissions of nitrous oxide (N2O), a potent greenhouse gas, are ~200 Gg. Poor N management results in Nr leaking into the environment, which has increased approximately 16-fold since 1961. One potential consequence is the disruption of ecosystem functioning. The balanced tradeoff between food production and reducing Nr input needs to be achieved. One solution to reducing Nr may be a holistic approach that optimizes N application rates and incorporates waste of one subsector as an input to another applying the principle of the circular economy.