Total Nitrogen Yield Research Articles

Routine stream monitoring data enables the unravelling of hydrological pathways and transfers of agricultural contaminants through catchments

Catchment-scale understanding of water and contaminant fluxes through all pathways is essential to address land use and climate change impacts on freshwater. However, few options exist to obtain this understanding for the many catchments worldwide for which streamflow and low-frequency water chemistry, but little other data exists.We applied the Bayesian chemistry-assisted hydrograph separation and load partitioning model (BACH) to 47 catchments with widely differing characteristics. As BACH relies on concentration differences between pathways, chemodynamic behaviour of a water constituent indicates its likely suitability as tracer. Typical tracers (e.g. silica, chloride) were unavailable, but Electrical Conductivity and a few monitored nutrients proved chemodynamic in most catchments.Using one of two tracer combinations (Total Nitrogen + Electrical Conductivity, Total Nitrogen + Total Phosphorus) allowed in 85 % of the catchments to estimate streamflow contributions by near-surface (NS), shallow groundwater (SGW), and deep groundwater (DGW) pathways and pathway-specific tracer concentrations and yields with acceptable confidence. In 46 catchments, at least two pathways contributed ≥20 % of the streamflow, and all three ≥20 % in 12 catchments, cautioning against the notion of a single ‘dominant’ pathway. In contrast to hydrometric hydrograph separation, BACH allows differentiation between ‘young’ (NS + SGW) and ‘old’ (DGW) water, which is crucial for the understanding of pollution in catchments with strong temporal gradients in land use intensity.Consistent with generally increasing land use intensity, and groundwater denitrification occurring in some catchments, Total Nitrogen (TN) concentrations were in most catchments higher in NS and SGW compared to DGW. In most catchments, the greatest fraction of the TN yield was conveyed by SGW (≈ 40–90 %). Exceptions were wet and hilly catchments under bush, where the NS transferred most of the very low yields, and three young volcanic catchments where the DGW transferred the majority of the yield due to particularly high DGW flow contributions.

Effects of extreme precipitation intensity and duration on the runoff and nutrient yields

Extreme precipitation and its subsequent natural disasters, including soil erosion and flood, have been confirmed to have major impacts on watershed hydrology and water quality. However, the contributions of the intensity and duration of extreme precipitation to the changes in runoff and nutrient yields have not been fully understood. In this study, we quantified the contributions of extreme precipitation intensity and duration to the changes in watershed runoff and nutrient yields through constructing a quantitative simulation protocol in a distributed hydrological model. The results showed that the historical extreme precipitation, runoff, and nutrient yields have similar inter-annual variation trends. Between 2010 and 2020, extreme precipitation events induced more than 90% of annual runoff and total phosphorus (TP) yields. Runoff and TP yields increased with the increase in extreme precipitation intensity, while total nitrogen (TN) yields did not always decrease linearly with reduced intensity. The impacts of the duration in extreme precipitation on runoff and nutrient yields were less than intensity. Nutrient yields from farmland were stably influenced by extreme precipitation intensity, while that from forestland and grassland have higher inter-annual variability. The contributions of duration to TP yields were higher in farmland and forestland than in grassland and urban and rural areas. Changes in the intensity and duration of extreme precipitation transformed watershed nutrient composition pattern. With the increase of intensity, the contribution ratio of farmland increased while that of urban and rural areas decreased. Moreover, the increase in intensity decreased the spatial autocorrelation degree of TN yields between sub-watersheds, increasing the spatial heterogeneity in TN yields. This study improved the understanding for the responses of runoff and nutrient yields to the variations in extreme precipitation characteristics, which is helpful for more targeted water quality management to cope with increasing climate extremes.

Yield and Nutrient Contents of Wheat, and Changes in Selected Soil Properties after 23 Years of Phosphorus Fertilizer Application

Effective nutrient and fertilizer management practices play a pivotal role in sustaining agriculture and mitigating the effects of climate change. These practices have a direct influence on soil fertility and crop productivity. This study investigated the long-term impacts of different phosphorus (P) fertilizer doses (0, 50, 100, and 200 kg P2O5 ha-1) on biomass yield and grain nutrient levels of wheat crops as well as on selected soil properties. The experiment was established in 1998 at the Research Center of Cukurova University in Adana, Southern Turkey. The wheat seeds were sown in October 2020 and harvested in May 2021. The experimental design was a randomized complete block, comprising 12 plots and replicated three times. Soil samples were collected at depths of 0-15 cm and 15-30 cm and subsequently analyzed for total carbon, organic carbon (OC), total nitrogen (TN), and the number of mycorrhizal spores. At harvest, wheat plant samples were collected for evaluating total dry biomass, grain yield and concentrations of potassium (K), zinc (Zn), total carbon (C), and total nitrogen (N) in the grain. The result showed that there was a linear increase in the total dry biomass of wheat, however, grain yield started to decline at P200. The wheat grain nutrient concentrations did not differ significantly across P doses, except for higher concentrations of Zn and K at P50 and higher values of grain C and N at P100. However, there was a linear decrease in Zn concentration as the applied P dose increased. The soil OC and soil TN at 0-5 cm were significantly changed relative to the control. The highest levels of soil OC and TN were observed at P100. The number of mycorrhizal spores did not significantly change with the P dose, but a decreasing trend was observed at higher doses. In conclusion, based on the observed parameters of wheat grain yield, total biomass production, grain nutrient concentrations, and soil OC storage, the application of 100 kg P2O5 ha-1 outperforms other P doses. However, the agronomic efficiencies, soil nutrient balance, and environmental effects of the applied P dose require more research.

Short-Term Effects of Bokashi Fertilizer with Reduced NPK Fertilization on Soil Fertility, Growth, and Yield of Rubber Trees

Rubber is currently the second major industrial crop in Malaysia after oil palm. The use of bokashi fertilizer (BF) on industrial crops is still not popular, and farmers rely mostly on chemical fertilizers (CFs) that are costly and hazardous to the environment. This research was conducted at Hevea plantation, Universiti Putra Malaysia, between August 2020–October 2021. The study was to assess the short-term effects of BF with reduced NPK fertilization on soil fertility, growth, and yield of rubber. Seven treatments (T) were involved. T1, T2, and T3 denote 4, 8, and 12 kg BF per pit. T4 was 1 kg NPK as control, whereas T5, T6, and T7 denote 4, 8, and 12 kg BF + 500 g NPK per pit, respectively. The variables observed included total nitrogen (TN%), total phosphorus (TP%), organic carbon (OC%), organic matter (OM%), exchangeable cations, microbial counts, tree girth, and dry rubber yield. The major findings indicated that applying 12 kg BF has raised the soil’s TN%, OC%, and OM% by 165, 171.4, and 172.0%, respectively, compared to NPK control. Also, adding 4 kg BF + 500 g NPK has increased the soil’s cation exchange capacity and TP% values by 107.8 and 42.9%, respectively, compared to the control. Adding sole bokashi increased the bacterial population by 22.2–133.3%. Rubber yield was better on trees treated with 12 kg BF, though this did not differ significantly from other treatments. Therefore, applying 12 kg BF or 4 kg BF + 500 g NPK can improve soil fertility and save costs from using inorganic fertilizer by at least 50%.

Evaluation of biogas production and pollutant removal efficiency of two-phase anaerobic digestion treating slaughterhouse effluent

Treatment of slaughterhouse and other agro-processing industry effluent has become important due to continuous global population growth and meat demand, particularly in developing countries, for sustainable biowaste management as well as value additions such as biofuel. Therefore, the objective of the study was to evaluate the performance of two-phase anaerobic digestion of slaughterhouse wastewater in terms of biogas production, methane yield, and removal efficiencies of organic matter, total nitrogen, and total phosphorus. Two consecutively connected 40 L galvanized metal anaerobic batch bioreactors were used to conduct the experiment. The total phosphorus removal efficiencies of hydrolytic-acidogenic reactor and methanogenic reactor were 13.34% and 16.58%, respectively. Total chemical oxygen demand, soluble chemical oxygen demand, biological oxygen demand, total dissolved solids, total solids, total suspended solids, volatile solids, and turbidity had overall removal efficiencies of 82.87, 88.53, 93.32, 75.35, 95.55, 98.95, 97.42 and 98.06%, respectively. Biogas production of 189.45 mL/day with methane and carbon dioxide compositions of 67.69% and 29.9%, respectively, was also achieved. It was concluded that the two-phase anaerobic digestion of slaughterhouse wastewater shows substantial organic matter removal efficiencies and biogas production.

Assessing the Effect of Spatial Variation in Soils on Sediment Loads in Yazoo River Watershed

Sediment deposition in river channels from various topographic conditions has been one of the major contributors to water quality impairment through non-point sources. Soil is one of the key components in sediment loadings, during runoff. Yazoo River Watershed (YRW) is the largest watershed in Mississippi. Topography in the watershed has been classified into two types based on land-use and slope conditions: Delta region with a slope ranging from 0% to 3% and Bluff hills with a slope exceeding 10%. YRW spans over 50,000 km2; the Soil and Water Assessment Tool (SWAT) was used to estimate soil-specific sediment loss in the watershed. Soil predominance was based on spatial coverage; a total of 14 soil types were identified, and the sediment contributed by those soils was quantified. The SWAT model was calibrated and validated for streamflow, sediment, Total Nitrogen (TN), Total Phosphorus (TP), and Crop yield for soybeans. Model performance was evaluated using the Coefficient of determination (R2), Nash and Sutcliffe Efficiency index (NSE), and Mean Absolute Percentage Error (MAPE). The performance was good for streamflow, ranging between 0.34 and 0.83, and 0.33 and 0.81, for both R2 and NSE, respectively. Model performance for sediment and nutrient was low-satisfactory as R2 and NSE ranged between 0.14 and 0.40, and 0.14 and 0.35, respectively. In the case of crop yield, model performance was satisfactory during calibration and good for validation with an R2 of 0.56 and 0.76 and with a MAPE of 11.21% and 10.79%, respectively. Throughout YRW, soil type Smithdale predicted the highest sediment loads with 115.45 tons/ha/year. Sediment loss in agricultural fields with a soybean crop was also analyzed, where soil type Alligator predicted the highest with 8.37 tons/ha/year. Results from this study demonstrate a novel addition to the scientific community in understanding sediment loads based on soil types, which can help stakeholders in decision-making toward soil conservation and improving the environment.

A seven‐year study on the effects of four tillage modes on soil physicochemical properties, microbial biomass, enzymatic activities, and grain yield in a rice–ratoon rice cropping system

AbstractRatoon rice is resource efficient to produce economically sound and environmentally sustainable rice production. However, there is no more information on the relative impact of soil tillage practices on soil physical and chemical properties, microbial biomass, and enzymatic activity, and grain yield in a rice–ratoon rice cropping system remains to be tested. Systematic study of soil under ratooning rice model is a problem to be solved in the development of ratooning rice model. This study primarily investigated the long‐term (from 2014 to 2020) changes in soil bulk density (BD), soil organic carbon (SOC) concentration, total nitrogen (TN) concentration, microbial biomass, β‐glucosidase activity (BG), urease activity (UR), and yield under four treatments: no‐tillage (NT), no plowing tillage + rotatory tillage (RT), plowing tillage in winter + rotatory tillage (PTW), and plowing tillage in spring + rotatory tillage (PTS). NT increased BD by 9.65%–12.97%, and RT increased the 20–40 cm soil layer BD by 8.80% in 2020, compared with the baseline initial value (in 2014). Plowing tillage (PT) time had no significant effect on BD. All tillage methods decreased the SOC concentration in the 0–20 cm soil layer, and only RT increased the TN concentration. PT was the only treatment that increased the SOC and TN concentrations in the 20–40 cm soil layer. Both the main‐season rice yield and the ratoon season rice yield ranked PTW > PTS > NT > RT, in which the main‐season rice yield increased by 28.15% and the ratoon season rice yield increased by 25.19% in PTW. Overall, the PTW treatment had the highest microbial biomass, enzyme activity, and grain yield compared with the other tillage methods. In conclusion, plowing tillage in winter + rotatory tillage is a more suitable tillage method under the mode of ratooning rice.

The effect of Trichoderma-enriched biofertilizer application on total nitrogen, organic carbon, and peanut (Arachis hypogaea L.) yield in Inceptisols

The addition of N, P, and K nutrients through the application of fertilizer that is not in accordance with recommendation dosage still happening nowadays. One of the efforts to minimize this problem is the use of biofertilizer. This research aimed to study the effect of Trichoderma-enriched biofertilizer (T-EB) application on total nitrogen, organic carbon, and peanut (Arachis hypogaea L.) yield in Inceptisols. The research was conducted at The Laboratory of Soil Chemistry and Plant Nutrition, Faculty of Agriculture, Universitas Padjadjaran, Jatinangor from May to October 2022. The design used was randomized block design (RBD) with nine treatments and three replications: (A)Control, (B)NPK Standard, (C) ½(T-EB)+1NPK, (D) ¾ (T-EB) + 1NPK, (E) 1(T-EB) + 1NPK, (F)1½(T-EB) + 1NPK, (G)1(T-EB) + ¾NPK, (H)1(T-EB) + ½NPK, (I)1(T-EB) + ¼ NPK. The results showed that the use of Trichoderma-enriched biofertilizer had a significant effect on soil total nitrogen, soil organic carbon, and peanut yield components compared to the control (without fertilizer) and NPK standard. A single dose of (T-EB) (2 kg/ha) effectively increased peanut yield when mixed with the NPK dose of standard fertilizer at ¾ (37.5 kg/ha). The use of (T-EB) at that dose can also reduce NPK usage in Inceptisols.

Meta-Analysis of Factors Affecting C-N Fractions and Yield of Paddy Soils by Total Straw Return and N Fertilizer Application

The effective use of nutrient-rich crop straw is an important way to use resources efficiently and to sustain agricultural development. This meta-analysis study collected and analyzed the data of 6788 observations published in 238 peer-reviewed papers to investigate differences in soil C-N fractions and yields of paddy soils under different straw-return amounts. This large dataset was also used to quantify the degree of influence of factors such as climate characteristics, soil properties, N fertilizer application rates, straw-rotting agent addition, rice varieties, and straw return methods. The results showed that straw return amounts improved soil alkaline-hydrolysable N (7%), total N (10%), organic C (11%), the C:N ratio (8%), rice N accumulation (12%), and overall yield (18%). The most significant effect was in northeast China fields for total soil nitrogen (TN) content and yield with increases of 13% and 22%, respectively. We also found more effective N utilization and a greater rice yield when 220–260 kg ha−1 N fertilizer was applied with 20–30 kg ha−1 straw-rotting agent with the total amount of straw return. These findings have important implications for choosing appropriate conditions and field management practices and to improve rice yield in China.

Nutrient and suspended solid concentrations, loads, and yields in rivers across the Lake Winnipeg Basin: A twenty year trend assessment

Study regionThe Lake Winnipeg Basin in the northern Great Plains of North America Study focusAssessment of trends in total nitrogen (TN), total phosphorus (TP) and total suspended solids (TSS) for 18 river stations in the Lake Winnipeg Basin for the period of 1996–2016 using a Weighted Regressions on Time, Discharge and Season (WRTDS) modeling approach. New hydrological insights for the regionWe observed rapidly increasing concentrations, loads, and yields of TN, TP and TSS at most of the evaluated river monitoring stations in the eastern half of the basin. In contrast, nutrient and suspended solid loads tended to exhibit decreasing or stationary trends at most of the more western stations. Trends in nutrients and suspended solids typically corresponded to discharge, particularly in the Red-Assiniboine subdrainage where rapidly increasing nutrient loads were almost exclusively associated with runoff patterns. Our findings will serve as a baseline against which future trend assessments can be compared. Moreover, our findings suggest that land management practices aimed at reducing nutrient loads to Lake Winnipeg should be prioritized towards the rivers of the eastern subdrainages of the Lake Winnipeg basin.

Identification of priority management areas for non-point source pollution based on critical source areas in an agricultural watershed of Northeast China

Identification of critical source areas (CSAs) for non-point source (NPS) pollution is of great significance for environment governance and prevention. However, the CSAs are generally characterized as great spatial dispersion, and spatially heterogeneous precipitation has a great influence on the spatial distribution of nutrient yields. Therefore, we identify the CSAs for nutrient yields in an agricultural watershed of Northeast China at hydrological response units (HRUs) scale based on the Soil and Water Assessment Tool (SWAT), assess the impacts of spatially heterogeneity of precipitation on the identification of the CSAs, analyze the sensitivity of nutrient yields to precipitation by scenarios analysis method, and further identify priority management areas (PMAs) that have poor ability to retain nutrients. The results showed that the CSAs for nutrient yields identified by uniform precipitation showed greater fluctuation range and coverage area than actual precipitation; the major prevention areas of total nitrogen (TN) yield were mainly distributed in regions nearby main stem of lower reaches, while that of total phosphorus (TP) yield were mostly located in urban area nearby outlet of the watershed; the identification of the PMAs significantly decreased the CSAs for TN yield, whereas that for TP yield was no significant difference with the CSAs. This study could provide scientific guidance for the NPS pollution governance and prevention.

Treatment of wet electrostatic precipitators wastewater by supercritical water oxidation

ABSTRACT The most commonly used method for treating gas emissions generated during the drying process in chipboard production plants is the Wet Electrostatic Precipitator (WESP). The wastewater generated from the WESP process is considered hazardous due to high pollutants loads and cannot be treated efficiently using conventional treatment methods, such as chemical and biological treatment, sedimentation, and various separation processes. Therefore, there is an urgent need to investigate a novel and efficient treatment method for WESP wastewater. Supercritical water oxidation (SCWO) has recently gained attention as a powerful technique that can remove organic pollutants from wastewater in a short time. In this study, the removal of pollutants from real WESP wastewater was investigated using the SCWO process. The effects of operating conditions; oxidation rate, reaction temperature, and process reaction time, were studied under different experimental conditions. For the SCWO process, optimum conditions 99%, the reaction time of 166 seconds, oxidant ratio of 1.78 and 600°C were determined for 95% yield of total organic carbon (TOC) and total nitrogen (TN). The overall results showed that the TOC and TN removal efficiencies increased with the increase of temperature, oxidant dosage, and reaction time. The result from this study indicated that SCWO is a promising and innovative technique for the treatment of WESP wastewater.

Challenges in linking soil health to edge-of-field water quality across the Great Lakes basin.

To better understand agricultural nutrient losses, we evaluated relationships between management (e.g., manure and tillage), soil health measurements, and resulting edge-of-field (EOF) surface water quality. This work was conducted before or early into conservation implementation at 14 Great Lakes Restoration Initiative EOF sites spanning Wisconsin, Michigan, Indiana, Ohio, and New York. Analyses of site characteristics (hydroclimate, management, catchment properties) along with 3 yr of soil health measurements (chemical, biological, and physical properties) showed EOF-nutrient export depended on both site and soil properties. A pattern emerged whereby sites not receiving manure and sites with manure defined opposite ends of several gradients for soil and water data. Sites receiving manure had increased microbial activity, organic matter (3.2 vs. 2.7%), and soil test phosphorus (P) (2.8 times more) relative to sites without manure. Suspended sediments (SS), total P (TP), and total nitrogen (TN) in EOF surface runoff varied over three to five orders. Multivariate analysis among sites showed covariant linkages between soil nutrients, soil C, microbial properties, and nutrients in EOF water. There were positive univariate relationships between water-extractable soil P and annual EOF-water concentrations and yields of orthophosphate, TP, TN, and SS (p<.01). Some soil physical properties (e.g., bulk density and infiltration) also covaried among sites but were not consistently related to runoff index or water yield variables. Given the observed among-site variability, we were not able to isolate desirable soil health signals on EOF surface water quality.

Assessment of BMPs by Estimating Hydrologic and Water Quality Outputs Using SWAT in Yazoo River Watershed

Water quality is a global concern; it is due to point and non-point source pollution. Non-point sources for pollution are mainly runoff from Agricultural and forest. To decrease nutrient inputs, management practices are implemented. Using Soil and Water Assessment Tool, water quality parameters can be quantified. Yazoo River Watershed is the largest watershed in Mississippi, which have impact on surface water quality due to large scale agriculture and forest lands. Model has been calibrated and validated for streamflow, sediment, Total Nitrogen (TN), Total Phosphorus (TP) for the USGS gauge stations in the watershed. Model efficiency was assessed with Coefficient of Determination (R2) and Nash-Sutcliffe Efficiency index (NSE). Best Management Practices (BMPs) were implemented throughout the watershed to simulate the impact of BMPs on streamflow, sediment, and nutrient yields. Vegetative Filter Strips (VFS), Riparian Buffer, combination of VFS and Riparian buffer and Cover Crops (CC) were tested for assessing the effective BMP in improving water quality. VFS, Riparian buffer and both (VFS + riparian) have no effect on streamflow, but they were able to decrease sediment, TN, and TP yields. Scenario with both VFS and Riparian buffer had the highest reduction capability as per varying width (5, 10, 15, and 20 m). For CC, Rye grass, Winter Barley and Winter Wheat (WW) were used, of which Rye grass had highest, 5.3% reduction in streamflow. WW has the highest Total Nitrogen reduction that is of 25.4%. CC also has significant reduction ranged between 10% to 11% for TP. This research would assist the Agricultural community to apply appropriate Management practices to improve water quality.

An enhanced rural anoxic/oxic biological contact oxidation process with air-lift reflux technique to strengthen total nitrogen removal and reduce sludge generation

Biological contact oxidation process is attractive and widely used in rural sewage treatment, due to its simplicity and relatively superior pollutants elimination efficiency. However, the effluent total nitrogen (TN) and excess sludge yield during the biological contact oxidation process still need to be intensified to stably satisfy the discharge standard. In the current study, an enhanced rural anoxic/oxic (A/O) biological contact oxidation process with air-lift reflux technique was properly established, which achieved better pollutant removal efficiency and lower excess sludge yield. Under the pathway of air-lift reflux technique, the TN and ammonia nitrogen (AN) removal capacity of A/O biological contact oxidation process were obviously increased from 66.5% and 73.8% to 95.3% and 80.6%, respectively, which should be attributed to the increasement of nitrifying bacteria (Nitrospira and Nitrosomonas) and denitrifying bacteria (Denitratisoma, Thauera, and Dechloromonas). The excess sludge yield was also decreased from 0.19 kg MLSS/kg COD (no reflux model) to 0.11 kg MLSS/kg COD (air-lift reflux model) since the degradation of returned oxic sludge in the anoxic tank, which was verified by stable isotope tracer analysis. The rural A/O biological contact oxidation process with air-lift reflux technique had great potential to strengthen TN removal and reduce sludge generation, which could provide a useful and easy-implement technology for rural sewage treatment.

Understanding the Combined Effects of Land Cover, Precipitation and Catchment Size on Nitrogen and Discharge—A Case Study of the Mississippi River Basin

Biological processes of rivers are strongly influenced by concentration and fluxes of nitrogen (N) levels. In order to restrain eutrophication, which is typically caused by urbanisation and agricultural expansion, nitrogen levels must be carefully controlled. Data from 2013 to 2017 were gathered from 26 sub-catchments in the Mississippi River basin to assess the effects that catchment size, land cover, and precipitation can have on the discharge and total nitrogen (TN) and how TN yields deviate from a generalised local trend. The findings indicated that land cover and precipitation had a determinative effect on area-weighted discharge (Qarea). More specifically, Qarea had significant positive (directly proportional) relationships with precipitation, forest, and urbanised land cover, and significant negative (inversely proportional) relationships with grassland/pasture and scrub/shrub land covers. Concurrently, the TN concentration significantly increased in the presence of agricultural land cover, but significantly decreased in forest land cover. The TN yield (TN concentration × Qarea) was largely determined by Qarea because the latter was observed to fluctuate more dramatically than concentration levels. Consequently, the TN yield exhibited the same relationships that Qarea had with precipitation and land covers. The TN yield changed significantly (p &lt; 0.05) and positively with instantaneous discharge across all sites. Nevertheless, the rate of TN yield variations with discharge displayed a significant (p &lt; 0.0001) negative (r2 = 0.80) relation with the catchment size. Ultimately, this study used discharge readings to facilitate the prediction of TN concentrations and yields across various catchment areas in the Mississippi River basin and provided a robust model for future research in this area.

Rotary and subsoiling tillage rotations influence soil carbon and nitrogen sequestration and crop yield

Long-term single tillage causes serious deterioration of land quality and reduction of crop yield. Tillage rotation can alleviate the problems caused by long-term single tillage. However, the effects of different tillage rotations are still very limited. A tillage rotation experiment was conducted in the North China Plain to evaluate the impacts of tillage rotation on soil organic carbon (SOC), soil total nitrogen (STN) and crop yield. There were eight treatments with two main factors: tillage practice (four types: rotary tillage (R, 2002–2017), subsoiling tillage (S, 2002–2017), rotary to subsoiling tillage (RS, 2015–2017) and subsoiling to rotary tillage (SR, 2015–2017)) and straw management (two types: straw return (F) and straw removal (0)). RSF treatment yielded the highest SOC, at 12.53 g/kg. RSF significantly increased SOC by 41.4% compared to RF, while SRF significantly reduced SOC by 11.1% compared to SF. In addition, RSF significantly increased STN content by 21.7% compared with that under RF. Compared with SF, SRF promoted the uniform distribution of soil nitrogen in the 0–20 cm soil layer. Among the treatments, the RSF treatment yielded the highest SOC stock (SOC&lt;sub&gt;S&lt;/sub&gt;) and STN stock (STN&lt;sub&gt;S&lt;/sub&gt;), which were 67.68 t/ha and 6.63 t/ha, respectively. Compared with RF treatment, RSF treatment greatly increased SOC&lt;sub&gt;S&lt;/sub&gt;, by 31.7%. Both tillage rotation treatments increased STN&lt;sub&gt;S&lt;/sub&gt; by 13.3% under RSF compared to RF, and by 2.3% under SRF compared to SF. In 2016, the annual yield was highest under RSF treatment at 19.80 t/ha. In 2017, the annual yield was highest under SF treatment at 21.37 t/ha, and next highest under RSF at 20.94 t/ha. In summary, long-term rotary tillage followed by subsoiling tillage combined with straw return (RSF) can significantly increase SOC, STN and crop yield. The rotation of rotary tillage to subsoiling tillage combined with the straw return is an effective measure for improving soil quality and increasing crop yields in the North China Plain.

Planting date and fertilizer type influenced soil quality indices and soybean (Glycine max L.) yields in derived savannah of Nigeria

Soybean is grown in many parts of Northern Nigeria, with little climatic challenges and soil organic matter. There is need to investigate possible influence of planting date of the crop in Southeastern Nigeria, an environment that is rather foreign to the crop. A study was carried out in 2018 and 2019 cropping seasons at Federal College of Agriculture, Ishiagu, Ebonyi State, to evaluate the influence of different planting dates and fertilizer types on selected soil physical and chemical properties, growth and yield of soybean. A split plot in a randomized complete block design was used with planting date (May and June) as the main plots, while six fertilizer types (poultry-droppings manure 5 t ha–1, swine-droppings manure 5 t ha–1, rice-husk dust 5 t ha–1, NPK 15:15:15 at 150 kg ha–1, urea at 100 kg ha–1 and the control) constituted the sub-plots. At crop maturity, some soil quality indices and pod and grain yields (t ha–1) of soybean were assessed. Soil organic carbon (SOC) and total nitrogen contents were significantly (p &lt; 0.05) influenced by both planting date and fertilizer type in 2018 and 2019, while soil pH was improved significantly (p &lt; 0.05) only by fertilizer type in these two cropping seasons. Mean-weight diameter of aggregates, soil bulk density and SOC stock as well as soybean yields were significantly (p &lt; 0.05) influenced by both planting date and fertilizer type in the two seasons. Generally, planting in May improved soil total nitrogen and soybean pod yield whereas planting in June improved the other soil quality indices and soybean grain yield, the best soil amendment in either case being poultry-droppings manure but sometimes parameter-specific. The choice of planting date (May or June) in soybean production in the derived savannah and the soil amendment to use in the enterprise thus has both agronomic and environmental implications. Such a choice would depend on the indices of soil quality and/or the aspects of soybean yields (pod or grain) whose improvements the farmer intends to achieve at crop maturity.

Pengaruh Pupuk Amonium Klorida terhadap N-Total Tanah, Serapan N, dan Hasil Jagung Manis (Zea Mays Saccharata Sturt) pada Inceptisol Jatinangor

In the past decade, Indonesian interest towards sweet corn has increased. This condition creates a wide market opportunity for sweet corn. However, sweet corn cultivation in Indonesia is often constrained by low soil fertility. One of the essential nutrients needed by sweet corn is nitrogen. Nitrogen can be obtained from inorganic fertilizers such as Ammonium Chloride (NH4Cl) fertilizer. This research aimed to determine the effect and the best dosage of Ammonium Chloride (NH4Cl) in increasing N-total, N uptake, and yield of Sweet Corn (Zea mays saccharata Sturt) of Talenta variety on Jatinangor Inceptisol. This experiment was conducted at the research field of Soil Chemistry and Plant Nutrition, Department of Soil Science and Land Resources, Faculty of Agriculture, Universitas Padjadjaran, Jatinangor from July to October 2020. The experimental design used in this research was Randomized Block Design (RDB), which consisted of nine treatments with 1 control treatment (without fertilizer), 1 standard single N, P, K fertilizer treatment, 3 dosages of Ammonium Chloride (NH4Cl) fertilizer treatment, and 4 combinations of Ammonium Chloride (NH4Cl) fertilizer with ¾ recommended dose of standard N, P, K fertilizer. The results showed that the combination of Ammonium Chloride (NH4Cl) fertilizer affected the total Nitrogen content, nitrogen uptake, and yield of sweet corn. Combination of 1 ¼ dose of Ammonium Chloride (NH4Cl) fertilizer with ¾ recommended dose of standard N, P, K fertilizer show the highest increase in total nitrogen (0,24%), nitrogen uptake (2,72 g per plant), and fresh weight of the corn cobs (0,42 kg per plant).

Kale (Brassica oleraceaL. var acephala) production in soilless systems in the Mediterranean region

The challenges faced by traditional agriculture led to the development of alternative agricultural systems such as soilless systems. This work aimed to assess the growth and yield components of kale under three soilless growing systems: Nutrient film technique set up vertically (T-vertical); Nutrient film technique set up horizontally (T-horizontal), and substrate coco bags (T-coco). The trials were conducted for two consecutive growing seasons (S1: Spring 2018 and S2: Fall 2019) in an unheated greenhouse. Irrigation supply, maximum plant uptake of water, and radiation use efficiency were evaluated for both seasons. The quantitative and qualitative parameters of the production were assessed in terms of yield ( kg per plant and kg per m²), number of leaves per plant, dry matter, protein content, nitrate level and leaf mineral composition. The main results showed that the maximum plant uptake was 0.30, 0.30 and 0.20 L m^-2 day^-1 respectively for T-vertical, T-horizontal and T-coco while the actual supply of water was 62.4, 32.28 and 3.27 L m^-2 day^-1, respectively. A significant difference was recorded for the number of leaves, yield components, dry matter, protein level, Radiation Use Efficiency and mineral composition of kale leaves was higher during fall than in the spring season. However, the nitrates level was much higher in spring than in fall. The T-vertical soilless system showed better yield (6.83±2.27 kg per m²), more proteins (2.53±0.31 g per100 g FW), and higher amounts of calcium (Ca), total nitrogen (N), manganese (Mn), and iron (Fe) than the other systems. The study demonstrated the potential of soilless production technologies in the coastal Mediterranean areas.