Soil nitrate-N Concentrations Research Articles

The Effect of Four Tillage Systems on Agronomic Properties and Soil Health Indicators in Southern Manitoba

Soil health encompasses the collective functioning of chemical, physical, and biological properties in soil. The extent to which soil management affects soil health and the links with agronomic outcomes remain unclear. This project aimed to understand the interrelations of tillage systems, soil health, and agronomic properties in Portage la Prairie, MB, Canada. Tillage systems were cultivation, deep tillage, raised beds, and vertical tillage. Soybean (Glycine max (L.) Merr), corn (Zea mays L.), and canola (Brassica napus L.) were all grown in 2020, 2021, and 2022. Crop yield, seed protein content, and seed oil content were measured each year. Soil samples were taken in spring 2021, fall 2021, and fall 2022 and analyzed for nitrate-N, ammonium-N, total N, ACE protein, water extractable organic N, water extractable total N, water extractable ammonium N, soil organic matter, soil organic carbon, calcium carbonate equivalent, CO2 burst, permanganate oxidizable carbon, water extractable organic C, pH, salts, Olsen P, K, S, sand, silt, and clay. Tillage system had a significant impact on agronomic properties in seven crop by sampling combinations. Tillage system effected soil nitrate-N concentration at five crop by sampling combinations, three more than any other soil property. Soybean agronomic properties correlated with soil health indicators more frequently than for corn and canola. This suggests that the utility of soil health indicators may be crop specific. Further research is needed to understand the mechanisms underpinning the ability of soil health indicators to predict agronomic outcomes and to benchmark soil health indicator values with time.

Effects of drip irrigation on yield, soil fertility and soil enzyme activity of different potato varieties in Northwest China.

The effects of different irrigation and fertilization on potato yield, soil fertility and soil enzyme activity of different varieties under drip irrigation fertilization mode were studied, which could provide support for selecting the best varieties in Northwest China. Three factors and three levels orthogonal experimental design method, a total of nine treatments. The three irrigation levels were W1 (100% crop evapotranspiration (ETC)), W2 (80% ETC) and W3 (60% ETC). The three fertilization levels were F1 (N-P2O5-K2O, 240-120-300 kg ha-1), F2 (180-90-225 kg ha-1) and F3 (120-60-150 kg ha-1). The three varieties were V1 (Feiuritar), V2 (Longshu7) and V3 (Qingshu 9). The results showed that different irrigation and fertilization had significant effects on potato yield, soil fertility and soil enzyme activity in root zone. The highest yield of T5 (80%ETC, 180-90-225 kg ha-1, Qingshu 9) was 49,222.3 kg ha-1. With the increase of fertilizer application rate, potato yield and soil enzyme activity in root zone increased first and then decreased, but soil electrical conductivity (SEC), soil nitrate-N content (SNNC), soil alkali-hydrolyzable nitrogen content (SAHC), soil available potassium (AK), soil available phosphorus (AP), soil ammonium-N content (SANC) and soil organic matter (SOM) in root zone increased continuously. The yield, soil catalase activity, soil urease activity and soil sucrase activity at W2 were 2.81% and 22.2%, 1.84% and 7.04%, 8.26% and 9.62%, 5.34% and 13.36% higher than those at W1 and W3, respectively. The overall trend of soil water content, soil nutrient content and enzyme activity in root zone was 0-20 cm >20-40 cm >40-60 cm soil layer. There were many soil factors affecting tuber yield, among which soil enzyme activity, pH value and root zone conductivity were the key factors. The results showed that T5 (80%ETC, 180-90-225 kg ha-1, Qingshu 9) was the best treatment to improve soil enzyme activity and yield.

Evaluating Critical Nitrogen Dilution Curves for Assessing Maize Nitrogen Status across the US Midwest

Plant N concentration (PNC) has been commonly used to guide farmers in assessing maize (Zea mays L.) N status and making in-season N fertilization decisions. However, PNC varies based on the development stage. Therefore, a relationship between biomass and N concentration is needed (i.e., critical N dilution curve; CNDC) to better understand when plants are N deficient. A few CNDCs have been developed and used for plant N status diagnoses but have not been tested in the US Midwest. The objective of this study was to evaluate under highly diverse soil and weather conditions in the US Midwest the performance of CNDCs developed in France and China for assessing maize N status. Maize N rate response trials were conducted across eight US Midwest states over three years. This analysis utilized plant and soil measurements at V9 and VT development stages and final grain yield. Results showed that the French CNDC (y = 34.0x−0.37, where y is critical PNC, and x is aboveground biomass) was better with a 91% N status classification accuracy compared to only 62% with the Chinese CNDC (y = 36.5x−0.48). The N nutrition index (NNI), which is the quotient of the measured PNC and the calculated critical N concentration (Nc) based on the French CNDC was significantly related to soil nitrate-N content (R2 = 0.38–0.56). Relative grain yield on average reached a plateau at NNI values of 1.36 at V9 and 1.21 at VT but for individual sites ranging from 0.80 to 1.41 at V9 and from 0.62 to 1.75 at VT. The NNI threshold values or ranges optimal for crop biomass production may not be optimal for grain yield production. It is concluded that the CNDC developed in France is suitable as a general diagnostic tool for assessing maize N status in US Midwest. However, the threshold values of NNI for diagnosing maize N status and guiding N applications vary significantly across the region, making it challenging to guide specific on-farm N management. More studies are needed to determine how to effectively use CNDC to make in-season N recommendations in the US Midwest.

Effects of Shallow Groundwater Depth and Nitrogen Application Level on Soil Water and Nitrate Content, Growth and Yield of Winter Wheat

The large amount of nitrogen application on the North China Plain has caused a serious negative impact on the sustainable development of regional agriculture and ecological environmental protection. Our aim was to explore the effects of nitrogen fertilization rate and groundwater depth on growth attributes, soil-water and soil-fertilizer contents, and the winter wheat yield. Experiments were carried out in micro-lysimeters at groundwater depths of 60, 90, 120, and 150 cm on the basis of 0, 150, 240, and 300 kg/ha nitrogen fertilization rates in the growth season for winter wheat. Results showed that plant height, leaf area index, soil plant analysis development, and yield without nitrogen application increased significantly with increases in groundwater depth. The optimal groundwater depths for growth attributes and yield were 60–120 cm and tended to be shallower with added nitrogen application. Soil moisture was lowered significantly with groundwater depth, adding a nitrogen application reduced soil moisture, and excessive nitrogen input intensified soil drought. Nitrate-N accumulation at the 120–150 cm depths was significantly higher than that at the 60–90 cm depths, and a 300 kg/ha (traditional nitrogen application rate) treatment was 6.7 times greater than that of 150 kg/ha treatment and increased by 74% more than that of the 240 kg/ha treatment at 60–150 cm depth. Compared with the yield of the 300 kg/ha rate, the yield of the 240 kg/ha rate had no significant difference, but the yield increased by 3.90% and 11.09% at the 120 cm and 150 cm depths. The growth attributes and yield of winter wheat were better, and the soil nitrate-N content was lower, when the nitrogen application rate was 240 kg/ha. Therefore, it can be concluded that nitrogen application can be reduced by 20% on the North China Plain.

Nitrogen addition altered the microbial functional potentials of carbon and nitrogen transformation in alpine steppe soils on the Tibetan Plateau

The microbial-mediated functional potentials of soil can be reflected by the abundance of corresponding microbial functional genes (MFGs). Few studies have simultaneously examined the responses of multiple key MFGs involving soil carbon (C) and nitrogen (N) transformation to N deposition, particularly under multiple application levels. In this study, we treated the alpine soil from the Tibetan Plateau with N fertilization at six addition rates. Absolute quantitative analysis was used to detect the abundance of MFGs related to soil C process: carbon dioxide (CO 2 ) fixation( cbbL ), methane (CH 4 ) oxidation ( pmoA ) and production ( mcrA ), and soil N process: ammonia oxidation (AOA- amoA : archaea amoA , AOB- amoA : bacterial amoA ), hydroxylamine oxidation ( hao ), nitrate, nitrite, nitric oxide and nitrous oxide (N 2 O) reduction ( narG / napA , nirS / nirK , norB , and nosZ ). The abundance of MFGs involved in both the soil C and N transformation processes were reduced as N rates increased (except AOB- amoA gene). Specifically, the abundance of the mcrA , AOA- amoA , nirK , norB , and nosZ genes were decreased non-linearly (U-shape) with the increasing N rates ( P < 0.05). The soil pH and dissolved organic C (DOC) concentration were positively correlated with the abundance of those MFGs, suggesting that the decreases in abundance of MFGs were more likely to be driven by changes of soil pH and DOC concentration. In contrast, the abundance of AOB- amoA gene increased linearly with the increasing N rates, which was strongly and positively correlated with soil nitrate-N (NO 3 – -N) concentration ( P < 0.001, r = 0.82). In addition, soil greenhouse gases emissions linked with the abundance of corresponding MFGs. Specifically, the soil CO 2 and N 2 O emissions were strongly and positively correlated with the AOB- amoA gene abundance ( P < 0.001, r = 0.78, r = 0.84), and the soil CH 4 emissions were significantly correlated with the pmoA ( P < 0.01, r = 0.60) and AOA- amoA ( P < 0.001, r = 0.72) gene abundance. The above results showed that the AOB- amoA gene had a positive response to increasing N rates, which was different from other genes. Indicating that elevated N deposition may improve the ammonia-oxidation process in alpine steppe soil mediated by AOB communities, and AOB communities may play an important role in donating the soil-atmosphere C and N exchange via CO 2 and N 2 O emissions. • The abundance of both C- and N-related MFGs were affected by N input rates. • N addition oppositely influenced on AOA- amoA and AOB- amoA gene. • The MFGs abundances were primarily regulated by soil DOC and pH under N addition. • Soil CO 2 and N 2 O emissions were strongly and positively correlated to AOB- amoA gene abundance.

Simplifying residual nitrogen (Nmin) sampling strategies and crop response

Globally, important nitrogen fertilizer decisions are often made at the early stages of plant development, when plants are not yet sufficiently indicative of their needs. Optimizing nitrogen fertilization of crops requires assessing the available soil mineral nitrogen content (Nmin) at the beginning of the season and was assessed exemplarily for wheat and maize. Since 2020 a mandatory soil Nmin analysis for each crop on a representative field is required in Germany in zones characterized by increased nitrate concentrations in the groundwater, encompassing approximately 28 % of the arable land. However, soil analysis is time-consuming, costly, and labor-intensive and requires further optimization beyond the current practice.In this study, wheat fields in 2018 and 2019 and maize fields in 2018 were sampled in a grid pattern in spring, and the soil nitrate-N content was determined in 30 cm layers down to 60 cm soil depth in 11 fields and further down to 90 cm soil depth in two of the fields. For each single and the combined soil depths, all fields could be sampled with a deviation of less than 10 kg nitrate-N ha−1 with only two soil samples. Overall, the reduced field-specific soil sampling strategy proved advantageous compared to crop-specific, regionally representative Nmin values offered by the official advisory authorities based on multiple averaged field investigations with an increased sampling intensity of 16 samples per field. Further, the reduced field-specific soil sampling strategy delivered more precise Nmin values by 11.2 kg nitrate-N ha−1 for wheat fields and slightly less precise values by 4.8 kg nitrate-N ha−1 for maize fields. The reduced field-specific soil sampling has great potential to reduce analysis and soil sampling costs. Nitrogen fertilization experiments supported the usefulness of the new simplified Nmin strategy. Multispectral in-season satellite imagery from Sentinel-2 could not adequately capture the spatial nitrate-N level differences and confirms soil samplings needs early in the season.Because most farmers base their fertilization strategy on regionally crop-specific aggregated Nmin values delivered by the official advisory system, we consider a simplified strategy to be more indicative of the field-specific soil Nmin status, which is eased by a markedly reduced sampling frequency and further simplifies the analysis by aggregating the separately analyzed soil depths to only one single depth. Further, currently available simplified on-farm analyses of the soil nitrate content allow for conducting more intensive field-specific soil Nmin analysis, thus contributing to improved nitrogen demand management and decreasing adverse environmental effects.

Soil nitrogen and phosphorus were greater in overlapping areas of fields in Alberta, Saskatchewan, Manitoba, and Ontario

A total of 344 soil cores were taken in annually cropped fields of Alberta, Saskatchewan, Manitoba, and Ontario from 2011 to 2013 in areas where the field shapes, or obstacles within fields, required the driving pattern of farm operations to overlap. Soil nitrate-N concentrations in overlapping areas were 60% greater, soil Olsen-P concentrations were 23% greater, and pH was 0.5 units greater at 0–15 cm depth compared with non-overlapping areas, suggesting smaller nutrient use efficiency and potential for greater nutrient loss.

Comparison of three measurement models of soil nitrate-nitrogen based on ion-selective electrodes

Ion-selective electrode (ISE) is a quick and low-cost method of soil nitrate nitrogen (N) detection. The measurement models of soil nitrate-N based on ISEs includes the linear regression model, multiple linear regression model and BP neural network model, and so on. Three models were analyzed in theory, measurement experiments of validation samples and soil nitrate-N concentrations were carried out in this study, and the measurement accuracies of the three models were compared. The results showed that, in the measurement experiments of validation samples and soil nitrate-N concentrations, BP neural network model had the highest accuracy (the average relative errors between results of the BP neural network model and the reference values were 5.07% and 8.81%, respectively) among the three models, multiple linear regression model had the second highest accuracy (the average relative errors between results of the multiple linear regression model and the reference values were 7.70% and 10.51%, respectively), linear regression model couldn’t exclude the interference of chloride ions so that it had the lowest accuracy (the average relative errors between results of the linear regression model and the reference values were 11.16% and 12.28%, respectively) among the three models. The BP neural network model can effectively restrain the interference of chloride ions, and it has a high accuracy for the measurement of soil nitrate-N concentration, so that the BP neural network model can be used to measure soil nitrate-N concentration accurately. Keywords: ion-selective electrode, soil nitrate-nitrogen, measurement model, accuracy DOI: 10.25165/j.ijabe.20201301.3599 Citation: Du S F, Pan Q, Xu Y, Cao S S. Comparison of three measurement models of soil nitrate-nitrogen based on ion-selective electrodes. Int J Agric & Biol Eng, 2020; 13(1): 211–216.

Comparison of three measurement models of soil nitrate-nitrogen based on ion-selective electrodes

Ion-selective electrode (ISE) is a quick and low-cost method of soil nitrate nitrogen (N) detection. The measurement models of soil nitrate-N based on ISEs includes the linear regression model, multiple linear regression model and BP neural network model, and so on. Three models were analyzed in theory, measurement experiments of validation samples and soil nitrate-N concentrations were carried out in this study, and the measurement accuracies of the three models were compared. The results showed that, in the measurement experiments of validation samples and soil nitrate-N concentrations, BP neural network model had the highest accuracy (the average relative errors between results of the BP neural network model and the reference values were 5.07% and 8.81%, respectively) among the three models, multiple linear regression model had the second highest accuracy (the average relative errors between results of the multiple linear regression model and the reference values were 7.70% and 10.51%, respectively), linear regression model couldn’t exclude the interference of chloride ions so that it had the lowest accuracy (the average relative errors between results of the linear regression model and the reference values were 11.16% and 12.28%, respectively) among the three models. The BP neural network model can effectively restrain the interference of chloride ions, and it has a high accuracy for the measurement of soil nitrate-N concentration, so that the BP neural network model can be used to measure soil nitrate-N concentration accurately. Keywords: ion-selective electrode, soil nitrate-nitrogen, measurement model, accuracy DOI: 10.25165/j.ijabe.20201301.3599 Citation: Du S F, Pan Q, Xu Y, Cao S S. Comparison of three measurement models of soil nitrate-nitrogen based on ion-selective electrodes. Int J Agric & Biol Eng, 2020; 13(1): 211–216.

Interactive Effects of Water and Fertilizer on Yield, Soil Water and Nitrate Dynamics of Young Apple Tree in Semiarid Region of Northwest China

Exploring the interactive effect of water and fertilizer on yield, soil water and nitrate dynamics of young apple tree is of great importance to improve the management of irrigation and fertilization in the apple-growing region of semiarid northwest China. A two-year pot experiment was conducted in a mobile rainproof shelter of the water-saving irrigation experimental station in Northwest A&amp;F University, and the investigation evaluated the response of soil water and fertilizer migration, crop water productivity (CWP), irrigation water use efficiency (IWUE), partial factor productivity (PFP) of young apple tree to different water and fertilizer regimes (four levels of soil water: 75%–85%, 65%–75%, 55%–65% and 45%–55% of field capacity, designated W1, W2, W3 and W4, respectively; three levels of N-P2O5-K2O fertilizer, 30-30-10, 20-20-10 and 10-10-10 g plant−1, designated F1, F2 and F3, respectively). Results showed that F1W1, F2W1 and F3W1 had the highest average soil water content at 0~90 cm compared with the other treatments. When fertilizer level was fixed, the average soil water content was gradually increased with increasing irrigation amount. For W1, W2, W3 and W4, high levels of water content were mainly distributed at 50~80 cm, 40~70 cm, 30~50 cm and 10~30 cm, respectively. There was no significant difference in soil water content at all fertilizer treatments. However, F1 and F2 significantly increased soil nitrate-N content by 146.3%~246.4% and 75.3%~151.5% compared with F3. The highest yield appeared at F1W1 treatment, but there was little difference between F1W1 and F2W2 treatment. F2W2 treatment decreased yield by 7.5%, but increased IWUE by 11.2% compared with F1W1 treatment. Meanwhile, the highest CWP appeared at F2W2 treatment in the two years. Thus, F2W2 treatment (soil moisture was controlled in 65–75% of field capacity, N-P2O5-K2O were controlled at 20-20-10 g·tree−1) reached the best water and fertilizer coupling mode and it was the optimum combinations of water and fertilizer saving.

Effects of nitrogen application rate and topdressing times on yield and quality of Chinese cabbage and soil nitrogen dynamics

ABSTRACTA good understanding of the relationship between vegetable quality and soil N balance is very important for proper nitrogen (N) management for crop productions. In this study, a field experiment was carried out to investigate the N application rate and times on Chinese cabbage yield and quality, N use efficiency, soil nitrate-N concentration, and soil pH. The experiment was implemented in a two-way factorial design and the two factors comprises of number of N applications (once, twice and three times, denoted as T1, T2 and T3) and N rates (15%, 30% and 45% less than conventional rates (CF), denoted as F1, F2 and F3, respectively). The treatments were also compared with a no-fertilizer blank and a control (CF) with a conventional N management practice. The results showed that the highest yield of cabbage (164.65 t hm−2), Vitamine C content (14.80 g 100 g−1 fresh mass), soluble sugar content (2.33 mg kg−1), plant N uptake (119.2 kg hm−2) were obtained under T3F1 treatment. Compared with CF treatment, T3F1 treatment significantly increased vegetable yield, vitamin C and soluble sugar content in fruit, and nitrogen use efficiency by 10.97%, 13.76% and 17.68%, and 18.76%, respectively. Nitrate-N content in cabbage was reduced by 7.55% in T3F1 treatment. With the reduced N application rate, soil pH gradually changed from 6.25 to 7.26. T3F1 treatment is a most suitable N management practice for vegetable production, in terms of higher vegetable yield and quality, soil N content, depressed soil acidification and nutrient uptake by Chinese cabbage.

Establishing soil nutrient distribution zones across free range egg farms to guide practical nutrient management strategies

Little is known regarding manure nutrient deposition in free range egg layer facilities. Consequently, a significant knowledge gap exists regarding how to best manage soil nutrient loading on these farms. Here, we report on soil nutrient properties across 14 Australian free range farms. Electromagnetic-induction (EM) mapping was performed at each farm to select soil sample locations which were collected at an average depth of 30 cm. EM data exhibited promising relationships with key soil properties. Measured soil properties were highly variable between and within farms. Soil nitrate-N (NO3-N) and Colwell-P (Col-P) concentrations ranged from 1 to 529 mg N kg−1 and 11 to 1856 mg P kg−1. Average NO3-N and Col-P concentrations across farms were 100 mg N kg−1 and 250 mg P kg−1 which exceed typical background nutrient levels and exceed requirements for dryland crop or pasture production. Farms with trees exhibited 2.6 × and 2.1 × greater NO3-N and Col-P concentrations than farms with no trees (P < 0.05), indicating trees attract birds to range areas resulting in higher manure deposition rates. Generalised nonlinear models were derived to describe soil nutrient concentrations with respect to shed location. These models revealed sharp nitrate and Col–P concentration decreases with increasing distance from sheds, with 50% of the NO3-N and Col-P concentration gradients restricted to a radius of <6 m (equating to an area of 0.05 ha) from the nearest shed (P < 0.05). Encouragingly for farms that pose a nutrient accumulation risk, these relatively small impacted areas can be managed with several options which we discuss in this paper.

Effects of Mulching and Nitrogen on Soil Nitrate-N Distribution, Leaching and Nitrogen Use Efficiency of Maize (Zea mays L.).

Mulching and nitrogen are critical drivers of crop production for smallholders of the Loess Plateau in China. The purpose of this study was to investigate the effect of mulching and nitrogen fertilizer on the soil water content, soil nitrate-N content and vertical distribution in maize root-zone. The experiment was conducted over two consecutive years and used randomly assigned field plots with three replicates. The six treatments consisted of no fertilizer without plastic film (CK), plastic film mulching with no basal fertilizer and no top dressing (MN0), basal fertilizer with no top dressing and no mulching (BN1), plastic film mulching and basal fertilizer with no top dressing (MN1), basal fertilizer and top dressing with no mulching (BN2) and plastic film mulching with basal fertilizer and top dressing (MN2). In the top soil layers, the soil water content was a little high in the plastic film mulching than that without mulching. The mean soil water content from 0 to 40 cm without mulching were 3.35% lower than those measured in the corresponding mulching treatments in 31 days after sowing in 2012. The mulching treatment increased the soil nitrate-N content was observed in the 0–40-cm soil layers. The results indicate that high contents of soil nitrate-N were mainly distributed at 0–20-cm at 31 days after sowing in 2012, and the soil nitrate-N concentration in the MN2 treatment was 1.58 times higher than that did not receive fertilizer. The MN2 treatment greatly increased the soil nitrate-N content in the upper layer of soil (0–40-cm), and the mean soil nitrate-N content was increased nearly 50 mg kg−1 at 105 days after sowing compared with CK treatment in 2012. The soil nitrate-N leaching amount in MN1 treatment was 28.61% and 39.14% lower than BN1 treatment, and the mulch effect attained to 42.55% and 65.27% in MN2 lower than BN2 in both years. The yield increased with an increase in the basal fertilizer, top dressing and plastic film mulching, and the grain yield increase ranged from 31.41% to 83.61% in two consecutive years. The MN1 and MN2 treatment is recommended because it increased the grain yield and improved the fertilizer use efficiency, compared with the no-mulching treatment.

A Protocol for Collecting and Constructing Soil Core Lysimeters.

Leaching of nutrients from land applied fertilizers and manure used in agriculture can lead to accelerated eutrophication of surface water. Because the landscape has complex and varied soil morphology, an accompanying disparity in flow paths for leachate through the soil macropore and matrix structure is present. The rate of flow through these paths is further affected by antecedent soil moisture. Lysimeters are used to quantify flow rate, volume of water and concentration of nutrients leaching downward through soils. While many lysimeter designs exist, accurately determining the volume of water and mass balance of nutrients is best accomplished with bounded lysimeters that leave the natural soil structure intact. Here we present a detailed method for the extraction and construction of soil core lysimeters equipped with soil moisture sensors at 5 cm and 25 cm depths. Lysimeters from four different Coastal Plain soils (Bojac, Evesboro, Quindocqua and Sassafras) were collected on the Delmarva Peninsula and moved to an indoor climate controlled facility. Soils were irrigated once weekly with the equivalent of 2 cm of rainfall to draw down soil nitrate-N concentrations. At the end of the draw down period, poultry litter was applied (162 kg TN ha(-1)) and leaching was resumed for an additional five weeks. Total recovery of applied irrigation water varied from 71% to 85%. Nitrate-N concentration varied over the course of the study from an average of 27.1 mg L(-1) before litter application to 40.3 mg L(-1) following litter application. While greatest flux of nutrients was measured in soils dominated by coarse sand (Sassafras) the greatest immediate flux occurred from the finest textured soil with pronounced macropore development (Quindocqua).

A Protocol for Collecting and Constructing Soil Core Lysimeters

Leaching of nutrients from land applied fertilizers and manure used in agriculture can lead to accelerated eutrophication of surface water. Because the landscape has complex and varied soil morphology, an accompanying disparity in flow paths for leachate through the soil macropore and matrix structure is present. The rate of flow through these paths is further affected by antecedent soil moisture. Lysimeters are used to quantify flow rate, volume of water and concentration of nutrients leaching downward through soils. While many lysimeter designs exist, accurately determining the volume of water and mass balance of nutrients is best accomplished with bounded lysimeters that leave the natural soil structure intact. Here we present a detailed method for the extraction and construction of soil core lysimeters equipped with soil moisture sensors at 5 cm and 25 cm depths. Lysimeters from four different Coastal Plain soils (Bojac, Evesboro, Quindocqua and Sassafras) were collected on the Delmarva Peninsula and moved to an indoor climate controlled facility. Soils were irrigated once weekly with the equivalent of 2 cm of rainfall to draw down soil nitrate-N concentrations. At the end of the draw down period, poultry litter was applied (162 kg TN ha-1) and leaching was resumed for an additional five weeks. Total recovery of applied irrigation water varied from 71% to 85%. Nitrate-N concentration varied over the course of the study from an average of 27.1 mg L-1 before litter application to 40.3 mg L-1 following litter application. While greatest flux of nutrients was measured in soils dominated by coarse sand (Sassafras) the greatest immediate flux occurred from the finest textured soil with pronounced macropore development (Quindocqua).

Effect of agro-industry by-product on soil fertility, tree performances and fruit quality in pear (&lt;em&gt;Pyrus communis &lt;/em&gt;L.)

Organic materials from agro-industry processes can be used in agriculture as a way to recycle materials that still maintain a high fertilizing value. The aim of the experiment was to evaluate the value of soil applied apple juice by-product as fertilizer for pear trees. A 3-year experiment was carried out in a mature pear orchard (cv Abbe Fetel grafted onto quince MC) in the Po valley (Italy), where the following treatments were compared: 1) unfertilized control; 2) mineral N fertilization (60 kg N ha −1 year −1 split in two spring applications); 3) apple juice by-product (1.3 t ha −1 year −1 , equal to 60 kg N ha −1 ), fully supplied at petal drop; 4) apple juice by-product, at twice the rate of the previous treatment. Apple juice by-product soil decomposition accounted for 12% in the first 6 months. At the end of the 24-month-assay, the decomposition accounted for 24% on total dry weight that makes 28% of initial C and 36% of initial N. Soil nitrate-N concentration was increased by the mineral N fertilizer, while the application of apple juice by-product increased microbial carbon. Tree growth, yield and fruit quality were not affected by treatments, while mineral N fertilization raised leaf and fruit N concentration. In conclusion, in our conditions the use of apple juice by-product did not show negative effects on tree performances and fruit quality, with some advantages related to the recycling of organic wastes in agriculture.

Phosphorus and nitrogen losses from poultry litter stacks and leaching through soils

Stacking poultry litter in fields prior to land application is a common practice that provides important logistical benefits to farmers, but may lead to environmental losses of nutrients. A 2-year field study was conducted to evaluate phosphorus (P) and nitrogen (N) losses from poultry litter stacks with and without a protective cover. Surface runoff from the litter stacks and leachate through two texturally contrasting soils (sand and silt loam) was monitored using a combination of runoff collectors and zero-tension lysimetry. Nutrient losses in surface runoff were small (total P < 3 g m−2; total inorganic N < 7 g m−2), particularly when compared with losses in leachate (total P < 60 g m−2; total inorganic N < 290 g m−2). Covering stacks reduced leachate total P losses by 25–100 times and total inorganic N losses by 25–770 times, such that leachate nutrient losses from covered stacks were similar to that in the controls with no manure stacking. Despite relatively small nutrient losses from litter stacks over the 2-year study, results point to substantial nutrient accumulation in soil after repeated stacking. Water-extractable P concentrations in upper 5-cm soils were similar between covered (120–240 mg kg−1) and uncovered stacks (140–250 mg kg−1), but soil nitrate-N concentrations were much higher under the covered stack (80–140 mg kg−1) than the uncovered stack (<5 mg kg−1). This study clearly points to benefits of covering litter stacks, but highlights long-term concerns with regard to soil nutrient accumulation.

Characteristics of maize biochar with different pyrolysis temperatures and its effects on organic carbon, nitrogen and enzymatic activities after addition to fluvo-aquic soil

In this study, the characteristics of maize biochar produced at different pyrolysis temperatures (300, 450 and 600°C) and its effects on organic carbon, nitrogen and enzymatic activities after addition to fluvo-aquic soil were investigated. As pyrolysis temperature increased, ash content, pH, electrical conductivity, surface area, pore volume and aromatic carbon content of biochar increased while yield, ratios of oxygen:carbon and hydrogen: carbon and alkyl carbon content decreased. During incubation, SOC, total N, and ammonium-N contents increased in all biochar-amended treatments compared with the urea treatment; however, soil nitrate-N content first increased and then decreased with increasing pyrolysis temperature of the applied biochar. Extracellular enzyme activities associated with carbon transformation first increased and then decreased with biochars pyrolyzed at 450 and 600°C. Protease activity markedly increased with increased pyrolysis temperatures, whereas pyrolysis temperature had limited effect on soil urease activity. The results indicated that the responses of extracellular enzymes to biochar were dependent on the pyrolysis temperature, the enzyme itself and incubation time as well.

Effects of mulching and nitrogen on soil temperature, water content, nitrate-N content and maize yield in the Loess Plateau of China

In the semi-arid region of the Loess Plateau in China, the use of alternative field management practices is essential for sustainable agriculture. The purpose of this study was to investigate the effect of mulching and fertilization on the soil temperature, soil water content, soil nitrate-N content and grain yield of maize. The experiment was conducted over three consecutive years and used randomly assigned field plots with five replicates. The six treatments consisted of no fertilizer without plastic film (CK), no fertilizer with plastic film (ZM), basal fertilizer without plastic film (BN), basal fertilizer with plastic film (BM), basal and top dressing without plastic film (BTN) and basal and top dressing with plastic film (BTM). The soil temperature of the 10-cm mulching treatment was significantly higher than that of the no-mulching treatment, and the average soil temperature of the mulching treatment increased by 2.3°C before July and nearly 1.2°C after July. The soil water content in the mulching treatment was significantly higher than that in the no-mulching treatment at 0–60cm, which was not significantly different from the 140–200cm depth. The trend in the soil nitrate-N content distribution revealed symmetrical shapes along the center of the furrows, and the standard symmetrical distribution reduced gradually with an increase in soil depth under the plastic film mulching conditions. The soil nitrate-N content under basal fertilizer was 1.65 times higher than that without fertilizer at 0–10cm at 36 days after sowing. The soil nitrate-N content in the topsoil was reduced from 48.67 to 30.77mg/kg after 58 days. We found that plastic film mulching with basal fertilizer increased maize yield by 10.61%, 9.48%, and 15.36%, and top dressing increased the yield by 16.61%, 20.94%, and 12.24% over the three consecutive years. A treatment involving plastic film mulching, basal fertilizer and top dressing is recommended. Further studies are required to investigate the effect of mulching on increased soil temperature, soil water content and soil nitrate-N content, which simultaneously affect yield, and to determine the effects on the field microclimate.

Evaluating four nitrous oxide emission algorithms in response to N rate on an irrigated corn field

In this study, the RZWQM2 (Root Zone Water Quality Model) was used to simulate the responses of N2O emissions to different Nitrogen application rates on an irrigated corn field from 2003 to 2006, in eastern Colorado, USA. Four different algorithms from the literature were coupled with RZWQM2 and compared for simulating N2O emissions during nitrification and denitrification processes. The RZWQM2 was first calibrated for corn yield, N uptake, soil water (0–10 cm) and soil Nitrate-N content (0–180 cm) and the simulated daily nitrification and denitrification rates were used to calculate N2O emission using the algorithms from DAYCENT, NOE (Nitrous Oxide Emissions),WNMM (Water and Nitrogen Management Model), and FASSET models. The best N2O emission was simulated when the fraction of N2O release from nitrification was modified by water filled pore space (WFPS) as in the NOE model and the fraction N2O release from denitrification was adopted from the DAYCENT model.