Comparison of Broiler Litter and Commercial Fertilizer at Equivalent N Rates on Soil Properties

A 3-year study was conducted to determine the effects of broiler litter relative to inorganic fertilizer on soil nutrient content and quality in an upland Loring silt loam soil. Treatments included annual broiler litter rates of 0, 2.2, 4.5, 5.6, 6.7, 10.1, and 13.4 Mg ha^?1 y^?1 and commercial fertilizer rates of 34, 68, 90, 112, 134, and 168 kg nitrogen (N) ha^?1 y^?1. Broiler litter application linearly increased soil total carbon (C), microbial biomass C, extractable soil phosphorus (P), potassium (K), soil cation exchange capacity (CEC), and the stability of soil aggregate. At the highest broiler litter rate, the stability of soil aggregate was 34% greater than inorganic fertilizer. Application of broiler litter or fertilizer N at rate greater than 6.7 Mg ha^?1 or 90 kg N ha^?1, respectively, exceeded plant N utilization potential as evidenced by higher end-of-season soil residual nitrate (NO₃)-N. Broiler litter is more effective in improving soil physical, chemical, and biological components than conventional fertilizer.     

Broiler and layer poultry manures as nitrogen sources for ‘douglas’ strawberry in a tunnel production system

Floor litter from laying hens (1‐year old) and from broiler chickens (8‐week old) were incorporated into soil and compared with ammonium sulfate [(NH₄)₂SO₄] and an unfertilized control treatment as sources of nitrogen (N) for ‘Douglas’ strawberry grown in a tunnel production system. Layer litter had 5.6% moisture, 3.9% N and 1.7% P, while broiler litter had 7.7% moisture, 4.9% N and 1.6% P; they were applied at a rate of 12.8 and 10.8 t/ha on wet basis, respectively, in August 1991. Ammonium sulfate was applied at 100 kg N/ha in three split applications during the growing season. ‘Douglas’ strawberry plants were transplanted on 15 November 1991 and fruits were harvested from 1 April to 10 June 1992. Nitrate‐nitrogen (NO₃‐N) concentrations at last harvest were comparable in the soil and leaf tissue among all treatments (P>0.05); leaf NO₃‐N, early in the harvest period, was highest (P<0.05) in the broiler treatment (8.55%) and lowest in the control (5.15%). Yields were increased (P<0.05) by the manure, with the broiler treatment yielding the highest and the control yielding the least.     

竹生物质炭和竹凋落物对毛竹林土壤营养元素和酶活性的影响

以广西壮族自治区桂林市华江乡内广泛分布的毛竹林土壤为研究对象,以竹生物质炭和竹凋落物作为外源碳,设置对照（CK）、低添加量生物质炭（1% BC）、高添加量生物质炭（2% BC）、低添加量凋落物（1% L）、高添加量凋落物（2% L）5个处理,进行为期两个月的室内培养试验,研究不同外源碳添加对毛竹林土壤营养元素和酶活性的影响。结果表明：与对照相比,竹生物质炭和竹凋落物添加均显著提高了土壤pH;竹生物质炭添加显著降低了而竹凋落物添加显著提高了土壤铵态氮（NH₄⁺-N）含量（P<0.05）,且高添加量（2% BC和2% L）的降低或提高作用更明显;不同外源碳添加均显著提高了土壤硝态氮（NO₃^–-N）含量,且凋落物添加的提高作用更明显;不同外源碳添加均显著提高了土壤有效磷（AP）含量,且高添加量的提高作用更明显;竹生物质炭添加对土壤可溶性有机碳（DOC）含量没有显著影响,但降低了土壤可溶性氮（DN）含量,而竹凋落物添加显著提高了土壤DOC和DN含量;不同外源碳添加对土壤微生物生物量碳（MBC）和氮含量（MBN）均没有显著影响,但降低了土壤蔗糖酶和脲酶活性。相关性分析表明,土壤pH、NH₄⁺-N、NO₃^–-N、DOC和DN是影响竹林土壤酶活性的关键性因子。     

Comparative evaluation of broiler and layer poultry manure for greenhouse lettuce production

Abstract

Disposing poultry manure from broiler and layer flocks by its incorporation into the soil was evaluated on greenhouse lettuce (Lactuca sativa L. cv. Paris Island cos). Floor litter that contains the manure mixed with sawdust and wood shaving, was 8 weeks old from broilers and one year old from layers. Broiler manure had 19% moisture and 5.5% N, while layer manure had 22% moisture and 3.7% N. Application of 27.5 ton/ha broiler manure and 18 ton/ha layer manure, on wet basis, gave comparable yield of lettuce as did an application of 100 kg N/ha from NH₄NO₃ in 2 split applications, and an unfertilized treatment. The manure was effective for lettuce growth 10 months after its incorporation in the soil. The highest yield was in manure treated plots, however, the lack of significant response in yield is due to the sufficient levels of soil NO₃‐N and available P. There was no effect on soil EC, pH, and available P due to the treatments; however, soil NO3‐N was significantly increased under all fertilized treatments. Leaf concentration of PO4‐P was not affected by the treatments, but NO3‐N was significantly increased under all fertilized treatments. It may be concluded that broiler and layer poultry manure when disposed of by soil incorporation, are equally effective as a fertilizer for a leafy crop such as lettuce.     

Apparent Use Efficiency of Nitrogen and Phosphorus from Litter Applied to Bermudagrass

More than 80% of broiler (chicken, Gallus gallus domesticus) litter produced annually is applied as a plant nutrient source, particularly for nitrogen (N) and phosphorus (P), to pastures. However, N losses during the process of litter N mineralization limit availability of N to crops. This study determined broiler litter N and P availability and apparent use efficiency (ANUE, APUE) to bermudagrass [Cynodon dactylon] during the first year after litter application. Treatments consisted of three litter rates (3.3, 6.6, and 13.2 Mg ha^?1), a commercial N fertilizer rate that provided 358 kg N ha^?1 as ammonium nitrate (NH₄NO₃), and an untreated control. Results showed bermudagrass dry-matter (DM) yield increased significantly with increase in litter rate. Commercial N fertilizer produced significantly greater DM yield than 3.3 and 6.6 Mg ha^?1 of litter but produced less DM yield than 13.2 Mg ha^?1 of litter. The overall average of ANUE from litter was 39% compared to the 59% from fertilizer. The mean litter N availabilities to bermudagrass during the first year after litter application were 48.5, 112.5, and 222 kg ha^?1, corresponding to the 3.3, 6.6, and 13.2 Mg ha^?1 litter rates, respectively. The overall mean of litter N mineralization, which was surface broadcast to bermudagrass plots during the first year, was 59.5% of the total litter N applied. The APUE, averaged across the rate and locations, was 13.6%, which was quite smaller than the ANUE of 39%. This finding of small APUE also validates the potential for P accumulation in soil after long-term animal manure application.     

Effects of Broiler Litter Management Practices on Phosphorus,Copper, Zinc,Manganese, and Arsenic Concentrations in Maryland Coastal Plain Soils

Abstract

The objective of this research was to assess the long‐term effects of broiler litter applications on soil phosphorus (P), copper (Cu), zinc (Zn), manganese (Mn), and arsenic (As) concentrations in Chesapeake Bay watershed Coastal Plain soils. Litter and soil samples were collected from 10 farms with more than 40 years of broiler production and from wooded sites adjacent to fields and were analyzed for P and metal contents. Averaged over farms, total P and metal concentrations in the litter were 12.8 g kg^?1 P and 332, 350, 334, and 2.93 mg kg^?1 Cu, Zn, Mn, and As, respectively. Surface (0–15 cm) soil pH values were greater than (5.7–6.4) the 0‐ to 15‐cm depth at wooded sites (3.5–4.3). Surface soil Bray 1 P values (149–796 mg kg^?1) in amended fields were greater than wooded sites (4.4–17 mg kg^?1). The 1N nitric acid (HNO₃)–extractable metal concentrations were higher in amended soils than in wooded areas and were 7.7–32, 5.7–26, 12.3–71, and 0.6–3.0 mg kg^?1 for Cu, Zn, Mn, and As, respectively, compared to 0.76–14, 4.6–22, 1.6–70, and 0.14–0.59 mg kg^?1 for the same metals, respectively, in wooded areas. Results from this study demonstrated that long‐term broiler litter applications have altered the chemical properties of the Coastal Plain soils of the Maryland Eastern Shore. Metal concentrations were low in the surface layer of amended fields and typically decreased with depth. Phosphorus additions rather than metals are most likely to contribute to the degradation of the Chesapeake Bay watershed.     

Changes in Soil Test Phosphorus from Broiler Litter Additions

Abstract

Nutrient surpluses on the Delmarva Peninsula have led to a continual accumulation of soil test phosphorus (STP), a potential source for transport of phosphorus (P) to surface waters. This article examines the effects of initial soil test P concentrations and broiler litter additions on STP accumulation. Broiler litter (BL) was applied at rates of 0, 2.5, 5, 7.5, and 10 g kg^?1 (dry weight) to three soils: an Evesboro sandy loam (Mesic, coated Typic Quartzipsamments), a Pocomoke sandy loam (coarse‐loamy, siliceous, thermic typic Umbraquults), and a Matapeake silt loam (fine‐silty, mixed, semiactive, mesic Typic Hapludults). Soils and BL were incubated for 16 weeks with subsamples analyzed after 4 and 16 weeks. There was a linear increase in STP (Mehlich‐3), water‐soluble P (WS‐P), iron‐oxide strip‐extractable P (FeO‐P), and Mehlich‐3 phosphorus saturation ratio (M3‐PSR) with broiler litter additions. Regression analysis indicated few significant differences in STP response to added BL between soils within the same soil group having different initial STP levels. Correlation analysis and stepwise regression indicated that increases in WS‐P and FeO‐P from added BL were more closely related to the degree of P saturation of the soil rather than traditional STP measurements. Therefore, decisions regarding manure placement within a watershed should be based on the potential P sorption capacity of the soil as well as potential P transport pathways when the goal is the reduction of P transfer to waterbodies.     

Effect of earthworm addition on soil nitrogen availability,microbial biomass and litter decomposition in mesocosms

The aim of the study was to determine the effect of adding two tropical earthworm species, Rhinodrilus contortus and Pontoscolex corethrurus, to mesocosms on the availability of mineral N (NH₄ ⁺ and NO₃ ^– concentrations), soil microbial biomass (bio-N), and the decomposition rates of three contrasting leaf litter species, in a glasshouse experiment. The mesocosms were filled with forest soil and covered with a layer of leaf litter differing in nutritional quality: (1) Hevea brasiliensis (C/N=27); (2) Carapa guianensis (C/N=32); (3) Vismia sp., the dominant tree species in the second growth forest (control, C/N= 42); and, (4) a mixture of the former three leaf species, in equal proportions (C/N=34). At the end of the 97-day experiment, the soil mineral N concentrations, bio-N, and leaf litter weight loss were determined. Both earthworm species showed significant effects on the concentrations of soil NO₃ ^– (p<0.01) and NH₄ ⁺ (p<0.05). Bio-N was always greater in the mesocosms with earthworms (especially with R. contortus) and in the mesocosms with leaf litter of H. brasiliensis (6 µg N g^–1 soil), the faster decomposing species, than in the other treatments (0.1–1.6 µg N g^–1). Thus, earthworm activity increased soil mineral-N concentrations, possibly due to the consumption of soil microbial biomass, which can speed turnover and mineralization of microbial tissues. No significant differences in decomposition rate were found between the mesocosms with and without earthworms, suggesting that experiments lasting longer are needed to determine the effect of earthworms on litter decomposition rates.     

Poultry litter and tillage influences on corn production and soil nutrients in a Kentucky silt loam soil

Broiler chicken (Gallus gallus) manure, a rich source of plant nutrients, is generated in large quantities in southeastern USA where many row crops, such as corn (Zea mays L.), are also extensively grown. However, the use of broiler manure as an economical alternative source of nutrients for corn production has not been extensively explored in this region. This study was conducted to examine the use of broiler litter as a source of nutrients for corn production, as influenced by tillage and litter rate, and any residual effects following application. In addition, the consequence of litter application to soil test nutrient levels, particularly P, Zn and Cu, was explored. The treatments consisted of two rates of broiler litter application, 11 and 22 Mg ha⁻¹ on a wet weight basis, and one rate of chemical fertilizer applied under no-till and conventional tillage systems. Treatments were replicated three times in a randomized complete block design. Corn was grown with broiler litter and inorganic fertilizer applied to the same plots each year from 1998 to 2001. In 2002 and 2003, corn was planted no-till, but only N fertilizer was applied in order to make use of other residual litter nutrients. Soil samples were taken yearly in the spring prior to litter application and 4 years after the cessation of litter application to evaluate the status of the residual nutrients in soil. Two years out of the 4-year experiment, broiler litter application produced significantly greater corn grain yield than equivalent chemical fertilizer application and produced similar grain yield in the other 2 years. Corn grain yield was significantly greater under no-till in 1999, but significantly greater under conventional-till in 2000, and no difference between the two tillage systems were observed in 1998 and 2001. With 4 years of litter application, Mehlich-3 P increased from an initial 18 mg kg⁻¹ to 156 mg kg⁻¹ with 11 Mg ha⁻¹ litter and to 257 mg kg⁻¹ with 22 Mg ha⁻¹ litter. For every 6 kg ha⁻¹ of P applied in poultry litter Mehlich-3 P was increased by 1 mg kg⁻¹. Modest increases in Mehlich-3 Cu and Zn did not result in phytotoxic levels. This study indicated that an optimum rate of broiler litter as a primary fertilizer at 11 Mg ha⁻¹ applied in 4 consecutive years on a silt loam soil produced corn grain yields similar to chemical fertilizer under both no-till and conventional tillage systems and kept soil test P, Cu and Zn levels below values considered to be harmful to surface water quality or the crop.     

Dicyandiamide effects on nitrification and total inorganic soil nitrogen in sandy soils

Abstract

Inhibition of nitrification in soil results in a decreased ratio of nitrate‐nitrogen (NO₃‐N) to ammonium‐nitrogen (NH₄‐N). If the conditions for NO₃‐N loss by leaching or denitrification exist, nitrification inhibitors should increase concentrations of total inorganic soil nitrogen (N) (TISN) (NH₄‐N + NO₃‐N). This can then result in plants taking up more N and developing more crop yield or biomass. This study examined whether inhibition of nitrification by dicyandiamide (DCD) would result in increased concentrations of TISN under field conditions. The effects of DCD on soil N were evaluated in hyperthermic sandy soils planted to potato (Solanum tuberosum L., cv. Atlantic). Treatments were factorial combinations of N as ammonium nitrate (NH₄NO₃) at 67, 134, and 202 kg N ha^‐1 and DCD at 0, 5.6, and 11.2 kg DCD ha^‐1. Soil NH₄‐N, NO₃‐N, and TISN concentrations were determined for up to five potato growth stages at two locations for two years for a total of 16 determinations (cases), i.e., four were not determined. The N form ratio [NO₃‐N/(NH₄‐N + NO₃‐N] x 100 was decreased in 10 of 16 cases, indicating that nitrification was inhibited by DCD. With two of these 10 cases, TISN concentration increased, but with four others, TISN concentration decreased with at least one N rate. With four of these 10 cases, inhibition of nitrification had no effect on TISN concentration. Under the conditions of these field studies, DCD inhibited nitrification more often than not. Inhibition of nitrification was, however, more likely to reduce TISN concentration than to increase it. This may have been due to DCD effects on immobization of applied NH₄‐N.     

Depletion of soil organic carbon and nitrogen under Pinus taeda plantations in Southern Brazilian grasslands (Campos)

Establishment of pine (Pinus spp.) plantations on grasslands could increase carbon (C) sequestration to counteract increased atmospheric carbon dioxide concentrations. In the grasslands of the southern Brazilian highland (Campos), large areas have been converted to Pinus plantations over the last 30 years. In order to assess the impact of this land‐use change on the amount and composition of soil organic matter (SOM), we investigated a grassland pasture site (G), and both an 8‐year‐old (P8) and a 30‐year‐old (P30) plantation with Pinus taeda. Soil samples down to 45 cm were analysed for texture, pH, soil organic carbon (SOC) and total nitrogen (N_tot) concentrations. Chemical composition of SOM was determined by using cross‐polarization magic angle spinning (CPMAS) ¹³C NMR spectroscopy. We analysed for stable C isotope (δ¹³C) and assessed the lignin composition by CuO oxidation. Additionally, contents of pyrogenic organic material (PyOM) were determined because the Campos is regularly burnt. Both pine plantations revealed relatively small SOC concentrations in the mineral soil of 72.6 mg g^?1 (P8) and 56.8 mg g^?1 (P30) and N_tot concentrations of 4.0 mg g^?1 (P8) and 2.9 mg g^?1 (P30) for the A horizon, while grassland showed significantly (P < 0.01) larger contents of 100.2 mg g^?1 for SOC and 5.9 mg g^?1 for N_tot. Accumulation of litter layers suggests decreased input of organic material into the mineral soil under pine, which was confirmed by the δ¹³C values and lignin composition. Smaller contents of vanillyl‐ (V), syringyl‐ (S), and cinnamyl (C)‐phenols, smaller ratios of S/V and C/V, and smaller ratios of acidic to aldehydic forms of V and S phenols indicated a high degree of decomposition of residual grass‐derived SOM in the upper part of the mineral soil (0–10 cm) under pine plantations. This was confirmed by CPMAS ¹³C NMR spectroscopy, showing an increasing Alkyl C/O‐Alkyl C ratio at the same depth. No significant changes in the contents of PyOM could be detected, but all sites tended to show the greatest concentrations at deeper soil depths > 15 cm, indicating a vertical relocation of PyOM. The results suggest that decomposition of residual SOM originating from grassland species contributes to the decrease of SOC and N_tot and to an acidification in the topsoil under pine plantations. We also suggest that slow litter decomposition and incorporation and the absence of fires at the plantations are additional reasons for the reduced amount of SOM. Depletion of SOM and the acidification of the topsoil may reduce the availability and supply of nutrients and diminish the C sequestration potential of the mineral soil.     

Low soil C:N ratio results in accumulation and leaching of nitrite and nitrate in agricultural soils under heavy rainfall

Nitrate (NO^-₃) and nitrite (NO₂^-) leaching threatens groundwater quality.Soil C:N ratio,i.e.,the ratio of soil organic carbon to total nitrogen,affects mineralization,nitrification,and denitrification;however,its mechanism for driving soil NO^-₃ and NO^-₂ accumulation and leaching remains unclear.Here,a field investigation in a fluvo-aquic soil and a soil column experiment were performed to explore the relation...     

Suspending Nitrogen Fertilization Reduces Residual Soil Nitrates in Dryland Cotton

Nitrogen (N) fertilizer use in cotton (Gossypium hirsutum L.) production is a potential source of nitrate (NO₃ ^?) contamination of soils, groundwater, and streams. The McConnell–Mitchell plots, a long-term study of cotton responses to N-fertilization and irrigation methods, were utilized to determine the NO₃ ^?-N in soil cropped to continuous cotton. The McConnell–Mitchell plots had a split-block experiential design. The main blocks of this test were irrigation methods. Each block of plots was irrigated using a single irrigation method for the entirety of the testing. Nitrogen fertilization rates were tested within each irrigation block. The soil NO₃ ^?-N content of two irrigation blocks, furrow flow (FI) and center pivot (CP), were compared to the dryland (DL) control block. Nitrogen treatments tested within each irrigation block ranged from 0 to 168.0 kg N ha^?1 in 33.6-kg N ha^?1 increments. Nitrogen treatments were tested for 18 years (1982 through 1999), discontinued for 4 years (2000 through 2003), and resumed in 2004. Soil samples were taken in the early spring (2000 and 2004) to a depth of 1.50 m in 0.15 m increments and analyzed for NO₃ ^?-N. Soil samples taken in 2004 were prior to any fertilization treatment. Irrigation method was found to influence the distribution of soil NO₃ ^?-N. Little accumulation of soil NO₃ ^?-N was observed in either irrigation block or under dryland production when N rates were less than 67.2 kg N ha^?1. Distribution of soil NO₃ ^?-N in the FI block was significantly different with sample depth and N treatment but not the interaction of depth and treatment in both 2000 and 2004. Presumably, the small and close values of the means and the greater variability of interactions compared to main effects precluded significant interactions. Differences in soil NO₃ ^?-N in the FI block after suspending N treatments for 4 years were similar to those found in 2000, although the soil NO₃ ^?-N was generally depleted in 2004 compared to 2000. The distribution of soil NO₃ ^?-N in the CP-irrigated block was dependent on the interaction of sample depth with N treatment in both 2000 and 2004. Soil NO₃ ^?-N values and differences tended to be too small to be of discernable or practical importance under CP irrigation. The distribution of soil NO₃ ^?-N in the DL block was dependent on the interaction of sample depth with N treatment in 2000 and 2004. Soil NO₃ ^?-N was minimal in the three lowest N treatments (0, 33.6, and 67.2 kg N ha^?1) in 2000. Greatest amounts of soil NO₃ ^?-N were found in conjunction with the 134.4 and 168.0 kg N ha^?1 treatments both years. Depletion of soil NO₃ ^?-N was evident in the surface 0.45 m of the 100.8, 134.4, and 168.0 kg N ha^?1 treatments under DL conditions in 2004.     

Comparison of soil nitrate extracted by potassium chloride and adsorbed on an anion exchange membrane in situ

Abstract

The 2M potassium chloride (KCl) extraction method used to measure soil nitrate (NO₃ ^‐‐N) concentrations in soils may introduce some artifacts caused by soil sampling, processing, and handling. Furthermore, this method provides soil NO₃ ^‐‐N concentrations for soil sampled at a particular time, whereas the dynamics of this anion in situ need to be better understood. In order to develop a reliable in situ method as an alternative, an anion exchange membrane (AEM) was tested for its ability to adsorb NO₃ ^‐‐N from a soil cropped to corn (Zea mays L.) and amended with manure or inorganic nitrogen (N). In a field study, we compared the amount of NO₃ ^‐‐N adsorbed on an AEM and extracted with the 2M KCl method. The AEM was calibrated in the laboratory and placed at 15‐cm soil depth for 2‐wk periods during the corn growing season. Nitrate adsorption on the AEM and KCl‐extractable NO₃ ^‐‐N were larger in the inorganic N treatment than in the manure or the control treatments throughout the growing season. The NO₃ ^‐‐N concentrations measured by the AEM method were correlated with NO₃ ^‐‐N extracted with 2M KCl (r² = 0.78***), suggesting that the AEM method could be used to measure NO₃ ^‐‐N concentrations in agricultural soils.     

Manure management practices applied to a seven‐course rotation on a sandy soil: effects on nitrate leaching

This experiment tested whether it was possible to incorporate broiler litter (BL) or cattle farmyard manure (FYM) into a 7‐yr arable rotation on a sandy soil without causing an increase in nitrate‐nitrogen (NO₃‐N) leaching. Four manure treatments (with adjusted fertilizer inputs), varying in frequency and timing of application, were imposed on the rotation and compared with a control that received inorganic fertilizer according to recommended rates. Over seven winters, the annual average NO₃‐N leached from the inorganic fertilizer treatment (control) was 39 kg/ha in 183 mm drainage. Total manure N loadings over the period of the experiment ranged between 557 and 1719 kg/ha (80–246 kg/ha/yr) for the four treatments. Three of the four manure treatments significantly increased NO₃‐N leaching over the rotation (P < 0.001). Annual applications of FYM (1719 kg/ha manure N or 246 kg/ha/yr) increased NO₃‐N leaching by 39%. We hypothesize that this was due to increased mineralization of the organic N accumulating from repeated FYM applications. BL applied each year (1526 kg/ha manure N or 218 kg N/ha/yr) increased NO₃‐N leaching by 52% above the control; BL applied 5 of 7 yr (972 kg/ha manure N or 139 kg N/ha/yr on average) and including inadvisable autumn applications increased leaching by 50%. BL applied in late winter or early spring every 2–3 yr (557 kg/ha manure N or 80 kg N/ha/yr on average) resulted in NO₃‐N leaching similar to the control. This suggests that to avoid additional NO₃‐N leaching from manure use in an arable rotation, manure should not be applied every year and autumn applications should be avoided; there are real challenges where manure is used on an annual basis.     

Changes in soil properties and their effects on maize productivity following<Emphasis Type="Italic"> Sesbania sesban</Emphasis> and<Emphasis Type="Italic"> Cajanus cajan</Emphasis> improved fallow systems in eastern Zambia

Improved fallows with leguminous trees have been developed in Southern Africa as a viable alternative to inorganic fertilizers but the changes in soil properties that are responsible for crop productivity improvement and implications of mixing litter and fresh leaves from the same tree species on soil fertility are not fully understood. Our objectives were to quantify (1) some changes in soil properties that are responsible for crop production improvement under improved fallow systems; (2) the N mineralization patterns of mixtures of litter and fresh leaves from the same tree species. The treatments used in the study were 2-year planted Sesbania sesban (sesbania) and Cajanus cajan (cajanus) and controls of natural fallow, continuous fertilized and unfertilized maize. At fallow clearing sesbania contributed 56 kg N ha^–1 through litter and fresh leaves. Sesbania (fresh leaves + litter) showed high N mineralization after 10 weeks compared to the mixture of cajanus fresh leaves with litter. Maize yields were significantly correlated with preseason NO₃^–-N and total inorganic-N content of the top 20-cm soil layer. Soil penetrometer resistance at 4 weeks after planting was lowest in the sesbania land-use system (2.2 Mpa), whereas the highest percentage of water-stable aggregates at fallow clearing and crop harvest was in sesbania (83%) and cajanus (77%), respectively. The improved soil conditions and N contribution of sesbania and cajanus fallows to the subsequent maize crop was evidenced by increased maize yields of between 170–200% over maize without fertilizer.     

Denitrification characteristics of subtropical soils in China affected by soil parent material and land use

Forty‐five soil samples were collected from rice paddy land (R), tea garden land (T), forestland (F), brush land (B), and upland (U) in Jiangxi province, a subtropical region of China. These soils were derived from Quaternary red earth (Q), Tertiary red sandstone (S), and granite (G). Their denitrification capacities were determined after treatment with 200 mg NO₃⁻‐N kg⁻¹ soil by measuring changes in NO₃⁻‐N content during a 28‐day anaerobic incubation under N₂ gas in the headspace, at 30°C. The subtropical soils studied here were characterized by generally small denitrification capacities, ranging from no denitrification capacity to complete disappearance of added NO₃⁻‐N within 11 days of incubation. With few exceptions, NO₃⁻‐N reduction with incubation time followed a first‐order relationship with reaction constants of 0 – 0.271 day⁻¹, but the data could be simulated better by a logarithmic relationship. Thus, denitrification capacity was determined by the reaction constant of the first‐order reaction, the slope of the logarithmic relationship, and the averaged NO₃⁻‐N reduction rate in the first 7 days of anaerobic incubation (ranging from 0 to 28.5 mg kg⁻¹day⁻¹), and was significantly larger in the soils derived from G than from Q and S for all land uses except for rice paddy land. Soil organic carbon and nitrogen availability are the key factors that determine differences in denitrification capacity among the three soil parent materials. Rice cultivation significantly promoted denitrification capacity compared with the other four land uses and masked the effect of soil parent materials on denitrification capacity. This is most likely due to increases in organic carbon and total N content in the soil, which promoted the population and biological activities of microorganisms which are able to respire anaerobically when the rice soil is flooded. Neither the increased pH of upland soil caused by the addition of lime for upland crop production, nor the decreased pH of the tea garden soil by the acidification effect of tea plants altered soil denitrification capacity. Our results suggest that land use and management practices favour soil carbon and/or nitrogen accumulation and anaerobic microorganism activities enhance soil denitrification capacity.     

Impacts of anthropogenic N additions on nitrogen mineralization from plant litter in exotic annual grasslands

Urban regions of southern California receive up to 45 kg N ha^-1 y^-1 from nitrogen (N) deposition. A field decomposition study was done using ¹⁵N-labelled litter of the widespread exotic annual grass Bromus diandrus to determine whether elevated soil N is strictly from N deposition or whether N mineralization rates from litter are also increased under N deposition. Tissue N and lignin concentrations, which are inversely related in field sites with high and low N deposition, determine the rate at which N moves from plant litter to soil and becomes available to plants. The effect of soil N on N movement from litter to soil was tested by placing litter on high and low N soil in a factorial experiment with two levels of litter N and two levels of soil N. The litter quality changes associated with N deposition resulted in faster rates of N cycling from litter to soil. Concentrations of litter-derived N in total N, NH₄⁺, NO₃⁻, microbial N and organic N were all higher from high N/low lignin litter than from low N/high lignin litter. Litter contributed more N to soil NH₄⁺ and microbial N in high N than low N soil. At the end of the study, N mineralized from high N litter on high N soil accounted for 46% of soil NH₄⁺ and 11% of soil NO₃⁻, compared to 35% of soil NH₄⁺ and 6% of soil NO₃⁻ from low N litter on low N soil. The study showed that in high N deposition areas, elevated inorganic soil N concentrations at the end of the summer N deposition season are a result of N mineralized from plant litter as well as from N deposition.     

Influences of nitrogen treatments and irrigation methods on soil chemical properties

Abstract

Changes in soil chemical properties were investigated in conjunction with an ongoing study of fertility and irrigation relationships of cotton. Four irrigation methods and five nitrogen fertilization rates were the primary focus of the study. The four irrigation regimes studied were: high frequency center pivot, low frequency center pivot, furrow irrigated, and unirrigated. Nitrogen rates were 0, 30, 60, 90, and 120 lb N/A. Soil samples were collected from each plot in 6‐in‐ increments to a depth of 24 in. in 1982 and again in 1986 after four years of continuous cotton production. The soil samples were analyzed for pH, organic matter (OM), P, K, electrical conductivity (EC), and NO₃ ^‐‐N. All background soil characteristics were found to vary with depth with the exception of NO₃ ^‐‐N. The follow‐up sampling and testing in 1986 showed significant differences in soil properties as a function of irrigation, N‐fertilization, depth, and their interactions. Nitrates were accumulated in the 18 to 24‐in. depth under high (120 lb N/A) fertilization, and in the 0 to 6‐in. depth under the four lower treatments (0, 30, 60, and 90 lb N/A). Soil pH was highest in the furrow and high frequency center pivot irrigated regimes and lowest in the unirrigated regime. Soil pH also decreased with depth. Electrical conductivity of the soil was highest in the high frequency regime and not significantly different among the other three irrigation methods. The 0M content of the soil was greatest in the high frequency regime but not significantly different in the low frequency, furrow, or unirrigated blocks. Soil 0M was found to decrease with depth through 18 in. in all cases. The P and K status of the soil was not changed as a result of the N fertilization or irrigation treatments.     

Reducing nitrous oxide emissions from a maize‐wheat sequence by decreasing soil nitrate concentration: effects of split application of pig slurry and dicyandiamide

Pig slurry (PS) is a valuable nitrogen (N) source for agricultural crops but the simultaneous supply of readily decomposable carbon and mineral N can result in large soil nitrous oxide (N₂O) emissions. Our objective was to determine the individual and combined effects of split PS application and addition of a nitrification inhibitor (dicyandiamide, DCD) on N₂O emissions and soil mineral N concentration in southern Brazil. Soil N₂O fluxes were measured from November 2010 to November 2011 from a maize (Zea mays L.)‐wheat (Triticum aestivum L.) sequence under various fertilizer treatments: no‐N control, PS applied in a single pre‐plant dose with or without DCD, PS split‐applied with or without DCD, and urea split‐applied. Cumulative N₂O emissions increased linearly (R² = 0.73) with increasing soil nitrate (NO₃^?) exposure, indicating that management practices aimed at reducing soil NO₃^? concentrations can decrease soil N₂O emissions. In total for the two crops, splitting PS reduced N₂O emission factors (EF) by 33%, whereas the addition of DCD reduced EF by 60 and 41% when PS was applied in single and split doses, respectively. However, splitting PS or adding DCD failed to reduce N₂O losses more than a single pre‐plant PS application in maize where background soil NO₃^? concentrations were large. The addition of DCD to PS applied as a single pre‐plant dose resulted in the largest reduction in soil N₂O emissions, whereas splitting PS with and without DCD resulted in significantly smaller abatements. Consequently, we concluded that adding DCD to PS in a single pre‐plant application is a better option than splitting PS applications for reducing soil N₂O emissions in no‐till cereal cropping systems in southern Brazil.