Residual Fertilizer Research Articles

Specific demands to the traction of cutting discs and furrow openers for the no-tillage system

The objective of this study was to identify the specific demands to the traction considering the work depth and the soil area mobilized by different associations between crop residue coulter discs and fertilizer furrow openers of crop planters, for the no-tillage system, subject to the ground speed. This experiment was conducted in a farm in the city of Santa Maria (Brazil – Rio Grande do Sul), in a soil classified as Red Ultisol with sandy loam texture. The experiment consisted of 24 combinations of treatments, in a factorial design of 2x3x4. The treatments were obtained by the interaction of furrowers (hoe furrow opener and double-disc opener) with three arrangements in relation to the cutting discs (without disc, smooth and offset fluted coulter) and speeds (1.11, 1.67, 2.22 and 2.78 m s -1 ). The combination of mechanisms was possible through the coupling in a mobile tool holder structure and by using an instrumented tractor as a power source. There was a significant influence of all factors on the variables. The double-disc presented the highest specific demand due to the depth, with 24.08 kN m -1 , while the hoe opener required 19.09 kN m -1 . For the need of traction per mobilized soil area, the double-disc opener also had superior requirement, 9.94% higher. Therefore, the hoe opener is more efficient in the use of traction. The use of cutting discs integrated with this furrow opener reduced the extension of the demands and provided lower speed influence, while the opposite happens for the double-disc furrow opener. Regardless of the combination, an increment of variables was observed with the increase of speed.

Optimising crop production and nitrate leaching in China: Measured and simulated effects of straw incorporation and nitrogen fertilisation

Abstract The sustainability of growing a maize—winter wheat double crop rotation in the North China Plain (NCP) has been questioned due to its high nitrogen (N) fertiliser use and low N use efficiency. This paper presents field data and evaluation and application of the soil–vegetation–atmosphere transfer model Daisy for estimating crop production and nitrate leaching from silty loam fields in the NCP. The main objectives were to: i) calibrate and validate Daisy for the NCP pedo-climate and field management conditions, and ii) use the calibrated model and the field data in a multi-response analyses to optimise the N fertiliser rate for maize and winter wheat under different field managements including straw incorporation. The model sensitivity analysis indicated that a few measurable crop parameters impact the simulated yield, while most of the studied topsoil parameters affect the simulated nitrate leaching. The model evaluation was overall satisfactory, with root mean squared residuals ( RMSR ) for simulated aboveground biomass and nitrogen content at harvest, monthly evapotranspiration, annual drainage and nitrate leaching out of the root zone of, respectively, 0.9 Mg ha −1 , 20 kg N ha −1 , 30 mm, 10 mm and 10 kg N ha −1 for the calibration, and 1.2 Mg ha −1 , 26 kg N ha −1 , 38 mm, 14 mm and 17 kg N ha −1 for the validation. The values of mean absolute deviation, model efficiency and determination coefficient were also overall satisfactory, except for soil water dynamics, where the model was often found erratic. Re-validation run showed that the calibrated Daisy model was able to simulate long-term dynamics of crop grain yield and topsoil carbon content in a silty loam field in the NCP well, with respective RMSR of 1.7 and 1.6 Mg ha −1 . The analyses of the model and the field results showed that quadratic, Mitscherlich and linear-plateau statistical models may estimate different economic optimal N rates, underlining the importance of model choice for response analyses to avoid excess use of N fertiliser. The analyses further showed that an annual fertiliser rate of about 300 kg N ha −1 (100 for maize and 200 for wheat) for the double crop rotation with straw incorporation is the most optimal in balancing crop production and nitrate leaching under the studied conditions, given the soil replenishment with N from straw mineralisation, atmospheric deposition and residual fertiliser. This work provides a sound reference for determining N fertiliser rates that are agro-environmentally optimal for similar and other cropping systems and regions in China and extends the application of the Daisy model to the analyses of complex agro-ecosystems and management practices under semi-arid climate.

Sustaining crop productivity while reducing environmental nitrogen losses in the subtropical wheat-maize cropping systems: A comprehensive case study of nitrogen cycling and balance

Balancing the nitrogen (N) budgets of agricultural systems is essential for sustaining yields at lower environmental costs. However, it is still rare to find reports on the total N budgets of agricultural systems including all N fluxes in the literature. Here, we conducted a comprehensive study on the effects of different N fertilizers (control, synthetic fertilizer, 60% synthetic fertilizer N plus 40% pig manure N, pig manure N applied at the same rate of 280kgNha−1 yr−1) on N pools, cycling processes, fluxes and total N balances in a subtropical wheat-maize rotation system in China by monitoring in situ N fluxes combined with field 15N-tracer and 15N isotope-dilution techniques. The warm and wet maize season was associated with significantly larger N losses via gaseous and hydrological pathways than the cooler and drier wheat season. Nitrate leaching and NH3 volatilization were the main N loss pathways, accounting for 78% and 93% of the annual hydrological and gaseous N losses, respectively. The field 15N tracing experiment showed that the wheat system had a high N retention capacity (∼50% of 15N application), although the N residence time was short. In the subsequent maize season, 90% of the residual 15N-labeled fertilizer in the soil that had been applied to the wheat system was utilized by plants or lost to the environment. The combined application of synthetic and organic fertilizers (pig manure) or application of pig manure resulted in significantly higher soil N retention and lower NO3− leaching, while yields remained unaffected. However, the application of manure resulted in larger NH3 volatilization losses compared with the application of synthetic fertilizer alone. Thus, our study suggests that a combination of synthetic and organic N fertilizers is suitable for sustaining agricultural productivity while reducing environmental N losses by fostering interactions between the soil C and N cycles.

Crop residue management and fertilization effects on soil organic matter and associated biological properties.

Returning crop residue may result in nutrient reduction in soil in the first few years. A two-year field experiment was conducted to assess whether this negative effect is alleviated by improved crop residue management (CRM). Nine treatments (3 CRM and 3N fertilizer rates) were used. The CRM treatments were (1) R0: 100% of the N using mineral fertilizer with no crop residues return; (2) R: crop residue plus mineral fertilizer as for the R0; and (3) Rc: crop residue plus 83% of the N using mineral and 17% manure fertilizer. Each CRM received N fertilizer rates at 270, 360, and 450kgNha(-1) year(-1). At the end of the experiment, soil NO3-N was reduced by 33% from the R relative to the R0 treatment, while the Rc treatment resulted in a 21 to 44% increase in occluded particulate organic C and N, and 80°C extracted dissolved organic N, 19 to 32% increase in microbial biomass C and protease activity, and higher monounsaturated phospholipid fatty acid (PLFA):saturated PLFA ratio from stimulating growth of indigenous bacteria when compared with the R treatment. Principal component analysis showed that the Biolog and PLFA profiles in the three CRM treatments were different from each other. Overall, these properties were not influenced by the used N fertilizer rates. Our results indicated that application of 17% of the total N using manure in a field with crop residues return was effective for improving potential plant N availability and labile soil organic matter, primarily due to a shift in the dominant microorganisms.

Estimating the gross budget of applied nitrogen and phosphorus in tea plantations

Abstract To increase crop yield, high fertilizer application rates have generally been used. The residual fertilizers potentially become a source of diffused pollution, and degrade soil and water quality. Such nonpoint source pollution is a major threat to reservoir eutrophication. The best management practices (BMPs) are usually used to prevent eutrophication; however, the environmental distribution of the applied fertilizers has not been understood properly. This could lead to a biased assessment of the rational quantity of nitrogen and phosphorous applied and the selection of BMPs. A field investigation of 32 plantations and 4 forests in the Feitsui Reservoir watershed, Taiwan, was conducted. Storm runoff water and soils were sampled, and a mass balance was used to demonstrate the gross nutrient budget. The results showed that when applying fertilizers of 2700 kg ha−1 in tea plantations only 18.3% of applied nitrogen and 5.5% of applied phosphorus were utilized by tea plants. Less than 5% of applied phosphorus was released in storm runoff, and more than 90% remained in the field. Approximately 30% of the nitrogen was lost through storm runoff, and 52% was stored in the soil mass. Therefore, reducing fertilizer application was recommended as the principal BMP, and collecting and treating storm runoff was suggested for controlling nitrogen pollution. The current management of soil erosion is an efficient measure for controlling phosphorus pollution.

Strategies to Provide Fertilizer for Both Production and Consumer Phases of Petunia

The objective of this study was to compare strategies using water-soluble fertilizers (WSF) and controlled-release fertilizers (CRF) to provide adequate nutrition during both production and consumer phases of petunia (Petunia ×hybrida). Strategies included a CRF with a second prill coating (DCT) that delayed initial nutrient release, compared with a conventional single-coated CRF (OSM) and WSF. Rooted cuttings of petunia were grown for 42 days in trade 1-gal (2.84-L) containers (the “production phase”) with WSF only, a low rate of combined WSF and substrate-incorporated OSM, or low and high label rates of WSF and top-dressed (TD) OSM (WSF + OSM TD), WSF and substrate-incorporated DCT (WSF + DCT), OSM, or a commercial blend of substrate-incorporated OSM and DCT (OSM + DCT). By the end of production phase after 42 days, all fertilizer strategies tested produced horticulturally acceptable plants in terms of chlorophyll index and number of flowers. In a subsequent “consumer phase,” plants were maintained in containers or were transplanted into a landscape and irrigated with clear water for 98 days. Plant performance [number of flowers, SPAD chlorophyll index, dry weight, and tissue nitrogen (N) level] was greater during the consumer phase in treatments with high rates of CRF compared with WSF only or lower rates of CRF. On the basis of nutrient release in a sand substrate without plants at 10, 21, or 32 °C, the DCT had delayed nutrient release compared with single-coated CRF. The release rates of all CRF products and the duration of the delay in release from DCT were temperature dependent. A partial budget found that the lowest cost treatment was WSF only at $0.02/container. Comparing at high application rates, using WSF + DCT ($0.085/container) was more expensive than incorporated OSM ($0.05/container) and had a similar cost to WSF + OSM TD ($0.084/container). The greatly improved consumer performance for plants with residual fertilizer compared with WSF provides an opportunity to add value and profitability if a slightly higher sales price could be obtained. Several fertilizer strategies are available depending on material and labor cost and availability and preferred crop management style.

English

The experiment was conducted in the 2013/14 season, in an experimental area of the C-Valle, in Palotina Municipal District, Parana State, Brazil. The cultivar used was Monsoy 6210 IPRO. The experimental design was a randomized block with four replications. The treatments consisted of basic fertilization (AB) in soybean sowing, AB + 20% AB + 40% AB + coverage with potassium, AB + 20% + coverage with potassium and AB + 40% + coverage with potassium. The variables evaluated for agronomic performance of soybeans were: Plant height, first pod height, number of pods per plant, yield and mass of one hundred seeds. Could not find significant differences in the variables analyzed. We conclude that the fertilization treatments were not effective for the increase of soybean grown in clay soil parameters. The crambe culture can be considered a culture that recycles nutrients and has good potential for the use of residual fertilizer from previous crops. Key words: Residual fertilizer, base fertilizer, nutritional requirements.

16S metagenomics reveals changes in the soil bacterial community driven by soil organic C, N-fertilizer and tillage-crop residue management

Conservation agriculture is a sustainable alternative to conventional agriculture. However, little is known about their effect on the environment and on the soil microbial community. It was established as a hypothesis that the bacterial community structure would be defined by the different agronomic practices. The objective of this study was, therefore, to investigate how crop residue management, tillage and fertilizer application affected the bacterial community and those groups involved in the degradation of applied plant residues, and increase the knowledge to predict the sustainability of a soil under a specific agronomic practice. Samples from an arable soil from the state of Sonora (México), i.e. Hyposodic Vertisol (Calcaric, Chromic) (IUSS Working Group, 2007), cultivated with wheat (Triticum spp.) and maize (Zea mays L.) in succession on conventionally tilled beds (CTB) with crop residue incorporated, permanent beds (PB) with residue burned or retained, left unfertilized or fertilized (300kgNha−1 for wheat and 103kgNha−1 for maize) was improved with dried young wheat plants to stimulate microbial growth, while the bacterial community structure and C and N mineralization were monitored in an aerobic incubation of 56 days. The soil organic C was significantly higher in the PB-residue retained treatments (average 13.1gkg−1 dry soil) compared with PB-residue burned (average 9.9gkg−1 dry soil) or CTB-residue incorporated (average 10.5gkg−1 dry soil), while pH and EC were significantly higher in the PB-residue burned (averages 8.85 and 1.06dSm−1) compared with the fertilized or unfertilized soil in PB-residue retained (averages 8.65 and 0.78dSm−1) or CTB-residue incorporated (averages 8.75 and 0.95dSm−1). In the unimproved soil, we found a significant effect of soil organic C, application of N fertilizer (highly significant on Nitrosovibrio) and tillage-residue management (principally in fertilized soil) on the bacterial community structure, but not in the improved soil. Treatment had no significant effect on the decomposition of the applied organic material, and on average 48% and 9.4% of the applied C and N, respectively, were mineralized in 56 days. Improvement of soil with wheat plant material increased mainly the relative abundance of Actinobacteria and Firmicutes and decreased a wide range of bacterial groups. On the bacterial level of genus, tillage-residue management was the most important defining factor of the bacterial community inducing differences in the genera involved in the degradation of applied plant material, i.e. Promicromonospora, Bacillus, Agromyces, Streptomyces, Sinorhizobium and Lysobacter, in different treatments. It was found that nitrogen fertilization and tillage-crop residue management defined the soil bacterial community structure in the unimproved soil, but were less determinant in improved soil, and these results supported the hypothesis tested. It was concluded that all the factors tested, i.e. tillage, crop-residue management and fertilizer application, affect the soil bacterial community structure, while the mineralization potential of the soil was preserved. This study contributes to our understanding of how soil use and management practices define the soil bacterial community structure.

Partial Substitution of Inorganic with Organic Fertilizer for Enhancement Fresh Fruit Bunch (FFB) Productivity in Oil Palm Plantations

Partial Substitution of Inorganic with Organic Fertilizer for Enhancement Fresh Fruit Bunch (FFB) Productivity in Oil Palm Plantations This paper describes the alternative fertilizer application in oil palm plantations of Riau Province, Indonesia. Expensive Inorganic fertilizer is needed in a considerable amount that farmers seek for alternatives. One of the solutions is by using organic palm residue fertilizer, as it is cheap, much available, and rich in nutrition. Fertilizer application is differentiated based on the four age category: young (3-8 years), juvenile (9-13 years), mature (14-20 years), and old (21-25 years). Three types of fertilizer, which is Inorganic fertilizer, organic fertilizer, and Inorganic fertilizer with partial substitution, was applied to each category. For a one year, several data such as type of fertilizer, fertilizer dose, fertilizing rotation and FFB productivity was observed monthly. The result shows that partial substitution of Inorganic fertilizer with organic fertilizer significantly raise FFB productivity, especially for young (Yplus) and old (Oplus) age category. It yields continuous improvement of FFB productivity, beginning from age young until old. Thus, the productive period of oil palm can last more than 25 years. Besides, better FFB productivity is achieved in young age category compared to usual production.

Groundwater Deterioration: The Simultaneous Effects of Intense Agricultural Activity and Heavy Metals in Soil

Groundwater deterioration due to agricultural activity is mainly attributed to intense fertilization, groundwater overpumping and seawater intrusion being more pronounced in coastal areas. Irrigation return water is one of the main sources of aquifers enrichment and it is expected to become the main source due to the simultaneous reduction of the amount/frequency of precipitation for many areas in Greece and the Mediterranean. The reduction of groundwater quantity and the simultaneous deterioration due to enhanced concentrations of fertilizer residues, such as nitrates, is well documented. Moreover, heavy metals of both anthropogenic and natural origin may be present in soils where agricultural activity takes place. As a result, groundwater is enriched in soluble species of heavy metals and this enrichment is a serious problem added on top of the above mentioned problems of groundwater deterioration. The relationship between heavy metals mobilization from soils to groundwater and the content of irrigation return water in solutes that influence the generation rates and mobility of heavy metals soluble species are discussed in this work. Data from groundwater samples taken in Psachna, Evia, a region characterized by elevated geogenic Cr in soils and intense agricultural activity, are presented. Two aspects of the problem are discussed: 1. The intense use of ammonium fertilizers: The pH reduction from the nitrification of ammonium fertilizers may be a serious factor influencing Cr(III) mobility. 2. The role of the ionic strength of the water (enhanced concentrations of cations due to seawater intrusion in the aquifer) in the mobility of Cr(III) by mechanisms of cation exchange.

Nitrogen recovery by cover crops in relation to time of planting and growth termination

Residual fertilizer nitrogen (N) in soil represents a potential environmental contaminant because of the risk of nitrate (NO3) leaching into ground water. Winter annual grass cover crops can conserve residual soil N; however, their ability to recover N greatly varies with management. A two-year field experiment in the North Carolina Coastal Plain on a State fine sandy loam (fine-loamy, mixed, thermic Typic Hapludult) compared dry matter (DM), N accumulation, and soil inorganic N following rye (Secale cereale L.), winter wheat (Triticum aestivum L.), triticale (Triticum secale L.), black oats (Avena strigosa L.), and fallow (native weeds) in relation to planting (October, November, and December) and growth termination (early March, early April, and late April/early May) dates and levels of residual soil N. Cover crop DM and N accumulations decreased with successive planting date delays (November and December) for each growth termination date in the following spring. In 2000, cumulative DM yields of October- and November-planted cover crops were 3.17 Mg ha−1 (1.41 tn ac−1) and 3.74 Mg ha−1 (1.66 tn ac−1), respectively, which were significantly greater than those of December-planted cover crops (1.90 Mg ha−1 [0.84 tn ac−1]) at the second growth termination date (early April). Cover crop N accumulation increased with a delay in growth termination, although the interaction between cover crop species and the planting date varied. October planting of rye and triticale showed greater N accumulation at a March growth termination date, averaging 37.8 kg N ha−1 (33.7 lb N ac−1) for rye and 37.6 kg N ha−1 (33.5 lb N ac−1) for triticale; these values were 7.8% and 14.1% higher than those of black oat and wheat, respectively, at the same planting and growth termination dates. November-planted wheat showed in the highest N accumulation (average, 57.9 kg N ha−1 [51.7 lb N ac−1]) at the late April/early May termination date; this was 3.8% to 7.9% higher than that of other species. In contrast, black oat showed a greater ability to scavenge soil residual N with a late planting and growth termination date combination (average, 58.7 kg N ha−1 [52.4 lb N ac−1]). The cover crop planting date affected soil inorganic N distribution at each termination date, with an October planting date resulting in lower soil profile inorganic N levels than November and December planting dates. Lower soil inorganic N concentrations were strongly associated with increases in cover crop DM and N accumulation for each growth termination date. These results should help growers identify the best niche for a cover crop with respect to recovering residual soil N in their various rotations.

Phosphorus use efficiency and management in agriculture

Phosphorus (P) is an essential element for all life, is essential for global food security, and is a limited, nonrenewable global resource, making its efficient use vitally important. There is a commonly held belief that P fertilizer is very inefficient because P recovery by crops in the year it is applied is often only 10-15%. The residual fertilizer P not recovered by the crop is believed to be permanently tied-up or “fixed” in the soil in forms not available to plants. However, field experiments do not support that view. The behavior of inorganic P in fertilizer when applied to the soil can be explained as contained in four pools of varying availability to plants based on its accessibility to plant roots and its extractability by soil test reagents. Phosphorus use efficiency can be assessed in several ways, but the “balance” method (i.e. partial nutrient balance) calculated as a P removal-to-input ratio and expressed as a percent best reflects the behavior of fertilizer P in soils and supports the concept of P transfer and availability within the four pools discussed. When determined by the balance method, P recovery is often in the range of 50-70% or even higher. Improving fertilizer P use and effectiveness is achievable through the implementation of fertilizer best management practices within the context of 4Rs—application of the right nutrient source, applied at the right rate, right time, and in the right place.

Long-term effect of residue return and fertilization on microbial biomass and community composition of a clay loam soil

SUMMARYA field study was carried out to examine the response of microbial communities of a clay loam soil to long-term (30 years) effects of residue return and fertilization. The experimental design was a split-plot arrangement of treatments, consisting of three residue treatments (crop residues returned at rates of 0, 2500 and 5000 kg/ha) in combination with eight fertilization treatments (control, no fertilizer; N, mineral nitrogen (N) fertilizer; P, mineral phosphorus (P) fertilizer; K, mineral potassium (K) fertilizer; NP, mineral NP fertilizer; NK, mineral NK fertilizer; PK, mineral PK fertilizer; and NPK, mineral NPK fertilizer). Soil microbial communities were characterized by phospholipid fatty acid analysis. Results indicated that the more crop residues were returned, the lower ratio of fungi to bacteria was observed. However, soil microbial biomass was only found to be significantly higher in plots with residues returned at a rate of 5000 kg/ha but not 2500 kg/ha. This suggested there was a threshold for microbial biomass to increase under residue return for the clay loam soil studied. The fertilization effect on soil microbial biomass gradually decreased with increases in the amount of crop residues returned. A significant composition change was observed under N fertilization. Structural equation modelling indicated that soil microbial communities were influenced directly by residue return and indirectly by residue-induced change in ratio of carbon to N and fertilization-induced change in soil pH.

The fate of urea nitrogen applied to a vegetable crop rotation system

To investigate the fate of urea nitrogen (N) applied to vegetable fields, three N rates, N0 (0 kg N/ha), N1(225 or 240 kg N/ha) and N2 (450 or 480 kg N/ha) were applied to a rotation system. Nitrogen fertilizer recovery (NFR), N residue in soil, and N losses were measured in situ. Higher N application rates resulted in lower NFR, and increased N residues in soil and losses. The NFR, Chinese cabbage, and eggplant were different in the N1 and N2 groups (P < 0.01). The ratios of N fertilizer residue at 0–60 cm deep ranged from 30.2 to 41.1 % (N1), and 33.1 to 57.7 % (N2). The N loss ratios were only 6.6 % (N1) and 11.9 % (N2), because of the lower precipitation rates and temperatures characteristic of its growing season; meanwhile, N losses were 31.1 and 37.4 % in cayenne pepper, and 24.1 and 29.2 % in eggplants in the N1 and N2 treatments, respectively. The main pathways of N loss were leaching, followed by gaseous losses; these were major pathways of N loss in seasons with lower precipitation rates. NH3 volatilization was correlated with soil temperature (P < 0.01), and N2O emissions were correlated with soil moisture in the N1 treatment and with soil NH4 +-N concentration in the N2 treatment (P < 0.01). Denitrification rates were correlated with soil moisture in the N0 and N1 treatments, and with NO3 −-N content in the N2 treatment (P < 0.01). Finally, loss due to runoff was correlated with precipitation (P < 0.01).

Anammox Process: the Principle, the Technological Development and Recent Industrial Applications

The ANAerobic AMMonium OXidation or Anammox process, nowadays becomes an important technology for industrial wastewater treatment plants, especially for an effective denitrification process. Anammox process has been widely known for its high efficiency in nitrogen removal in various kinds of wastewater. This review described the details of Anammox process, including biochemical characteristics, technical development, and its applications based on literature studies. Additionally, applications of Anammox process in wastewater treatment in different types of bioreactors were discussed. Finally, three typical applications of Anammox process in nitrogen removal for landfill leachate, fertilizer residues from agricultural activities and petrochemical industrial wastewater treatment were analyzed.

Evaluation of the AnnAGNPS Model for Predicting Runoff and Nutrient Export in a Typical Small Watershed in the Hilly Region of Taihu Lake.

The application of hydrological and water quality models is an efficient approach to better understand the processes of environmental deterioration. This study evaluated the ability of the Annualized Agricultural Non-Point Source (AnnAGNPS) model to predict runoff, total nitrogen (TN) and total phosphorus (TP) loading in a typical small watershed of a hilly region near Taihu Lake, China. Runoff was calibrated and validated at both an annual and monthly scale, and parameter sensitivity analysis was performed for TN and TP before the two water quality components were calibrated. The results showed that the model satisfactorily simulated runoff at annual and monthly scales, both during calibration and validation processes. Additionally, results of parameter sensitivity analysis showed that the parameters Fertilizer rate, Fertilizer organic, Canopy cover and Fertilizer inorganic were more sensitive to TN output. In terms of TP, the parameters Residue mass ratio, Fertilizer rate, Fertilizer inorganic and Canopy cover were the most sensitive. Based on these sensitive parameters, calibration was performed. TN loading produced satisfactory results for both the calibration and validation processes, whereas the performance of TP loading was slightly poor. The simulation results showed that AnnAGNPS has the potential to be used as a valuable tool for the planning and management of watersheds.

Fate of residual 15N-labeled fertilizer in dryland farming systems on soils of contrasting fertility

Up to 50% of nitrogen (N) fertilizer can remain in soil after crop harvest in dryland farming. Understanding the fate of this residual fertilizer N in soil is important for evaluating its overall use efficiency and environmental effect. Nitrogen-15 (15N)-labeled urea (165 kg N ha−1) was applied to winter wheat (Triticum aestivum L.) growing in three different fertilized soils (no fertilizer, No-F; inorganic nitrogen, phosphorus and potassium fertilization, NPK; and manure plus inorganic NPK fertilization, MNPK) from a long-term trial (19 years) on the south of the Loess Plateau, China. The fate of residual fertilizer N in soils over summer fallow and the second winter wheat growing season was examined. The amount of the residual fertilizer N was highest in the No-F soil (116 kg ha−1), and next was NPK soil (60 kg ha−1), then the MNPK soil (43 kg ha−1) after the first winter wheat harvest. The residual fertilizer N in the No-F soil was mainly in mineral form (43% of the residual 15N), and for the NPK and MNPK soils, it was mainly in organic form. The loss rate of residual 15N in No-F soil over summer fallow was as high as 48%, and significantly (P < 0.05) higher than that in the NPK soil (22%) and MNPK soil (19%). The residual 15N use efficiency (RNUE) by the second winter wheat was 13% in the No-F soil, 6% in the NPK soil and 8% in the MNPK soil. These were equivalent to 9.0, 2.0 and 2.2% of applied 15N. The total 15N recovery (15N uptake by crops and residual in 0–100 cm soil layer) in the MNPK and NPK soils (84.5% and 86.6%, respectively) were both significantly higher than that in the No-F soil (59%) after two growing seasons. The 15N uptake by wheat in two growing seasons was higher in the MNPK soil than in NPK soil. Therefore, we conclude that a high proportion of the residual 15N was lost during the summer fallow under different land management in dryland farming, and that long-term combined application of manure with inorganic fertilizer could increase the fertilizer N uptake and decrease N loss.

Influence of legume residue and nitrogen fertilizer on the growth and yield of sorghum (Sorghum bicolor (L.) moench) in Bauchi state, Nigeria.

A field experiment was conducted at the Abubakar Tafawa Balewa University teaching and research farm Bauchi (10o 22' N and 9o 47'E) and also at Bulkachuwa village of Katagum LGA. (11o 38'N and 10 o 31'E) both in Bauchi state, during the rainy seasons of 2011 and 2012 to determine the influence of legume residue and nitrogen fertilizer on the growth and yield of sorghum (Sorghum bicolor (L.) Moench). The treatments consist of two legumes (cowpea and soybean), nitrogen fertilizer applied at the rate of 0, 15, 30 and 60kgN/ha, both used to determine the performance of a Sorghum (variety; KSV 8). The legumes were sown in the first year while using the same site/plots, sorghum was then sown in the second year. The experiment was laid out in both years using Randomized Complete Block Design (RCBD) replicated three times. No data were collected on the legumes in the first year while data collected on sorghum in the second year included; plant height, number of leaves, 1000 grain weight and grain yield (kg/ha). The results of the experiment revealed that, growing sorghum on cowpea and soybean residue had significant (P≤0.05) effect on all the characters measured than on fallow. The results further revealed that, application of nitrogen fertilizer at the rate of 60kgN/ha gave significantly (P≤0.01) higher effects on all the characters studied than when the other rates were used. Control plots on the other hand recorded the least. It was also observed that, siting the experiment at Bauchi significantly (P≤0.05) produced higher yield than when the experiment was carried out at Bulkachuwa. Studies on interaction revealed that, irrespective of the location used, application of 60kgN/ha following cowpea and soybean in rotation significantly (P≤0.01) increased yield of sorghum. Based on the results obtained, application of 60kgN/ha as top dress to sorghum grown on cowpea or soybean residue should be adopted by farmers in and around Bauchi state for higher yield.

Evaluating Postharvest Sugarcane Residue Amendment and Broadcast Fertilizer Application as Techniques to Enhance Dune Grass Establishment and Expansion

Coastal dunes are valuable components of barrier shorelines, but establishing the appropriate vegetation to facilitate the growth and maintenance of this important habitat is difficult due to the presence of consistent stressors, including nutrient, water limitation, and salt spray. We examined whether the amendment of dune soils with postharvest sugarcane residue and broadcast fertilizer would enhance the establishment and growth of two key dune grass species, bitter panicum ( Panicum amarum ) and sea oats ( Uniola paniculata ), in natural and created sand dunes in coastal Louisiana in a short-term field study. The benefit of broadcast fertilizer addition to the growth of both species was evident, as was a tendency for greater establishment and growth of bitter panicum than sea oats. The created dune environment was significantly less favorable than the natural dune system in terms of soil characteristics and plant growth responses. Interestingly, postharvest sugarcane residue, which we hypothesized would improve dune grass establishment and growth by increasing soil organic matter and thereby soil moisture retention, failed to enhance dune grass growth. We conclude that dune restoration efforts in coastal Louisiana would benefit from the inclusion of a broadcast fertilizer regime, particularly in terms of accelerating bitter panicum growth and establishment. However, application of postharvest sugarcane residue does not appear to provide the same benefits to dune grass establishment and expansion as has been shown with other organic amendments.

Relationship between mineralized nitrogen during anaerobic incubations and residual effect of nitrogen fertilization in two rice paddy soils in Chil

An important N source for rice (Oryza sativa L.) is mineralization of the organic forms of N present in the soil. The correct N determination will help to optimize the amount of fertilizer used. Our objective was to calculate an index that relates crop N uptake from previous N fertilization and N mineralized in rice paddy soils. To do so, we used two rice paddy soils, Alfisol and Vertisol, in Chile under different anaerobic incubation times and temperatures. We determined both soil mineralization and residual effect of fertilization in the previous season under field and laboratory conditions in an Alfisol and a Vertisol managed with a rice monocrop. Anaerobic incubations were carried out at 20 and 40 °C; and at five different times (0, 7, 14, 21, and 28 d). Our results indicate that residual fertilization affects N mineralization, which increases in both paddy soils when compared with the control without N. In the Alfisol it fluctuates between 6.1 and 13.3 mg N-NH4+ kg-1, whereas in the Vertisol ranged between 18.4 and 28.0 mg N-NH4+ kg-1. Crop N uptake as a residual effect of applied N ranged between 29.3 and 33.9 kg N ha-1 in the Alfisol and 28.3 and 45.8 kg N ha-1 in the Vertisol. Thus, N mineralization is mainly affected by incubation time, temperature, and N fertilization rate of the previous crop season; it can be represented by quadratic models with high determination values, R2 = 0.73** and R2 = 0.78**, for Alfisol and Vertisol, respectively. Moreover, we found that the best incubation time and temperature were 7 d at 20 °C and 21 d at 40 °C, for the Altisol and Vertisol, respectively. In addition, there are potential savings in the next rice crop season from 0.86 to 0.43 kg N applied for each 1 mg N kg-1 mineralized in the Alfisol and Vertisol, respectively. We conclude that crop N uptake was related to mineralized N and that the equation here developed that relates them is a good predictor to optimize fertilizer use in rice paddy fields.