渭北旱塬不同田间管理措施下冬小麦产量及水分利用效率

水分是限制旱地作物产量最主要的因素,提高自然降水利用效率是增加旱地作物产量的有效途径。2001～2003年在渭北旱塬粉砂壤土上的田间试验研究表明,不同田间管理措施对冬小麦的产量及水分利用效率有显著的影响。秸秆覆盖不仅增加雨水入渗,提高上层土壤含水量,而且促进水分向下运输。在覆盖第二年小麦产量较常规种植显著增加,同时覆盖下土壤有机质含量有较快增加的趋势。夏季休闲期种植填闲作物将不影响下一季作物的水分状况,短期内填闲作物对土壤有机质,小麦产量及水分利用效率也没有影响。     

热带农业生态系统土壤肥力与植物养分综合管理研究进展

The greatest challenge for tropical agriculture is land degradation and reduction in soil fertility for sustainable crop and livestock production.Associated problems include soil erosion,nutrient mining,competition for biomass for multiple uses,limited application of inorganic fertilizers,and limited capacity of farmers to recognize the decline in soil quality and its consequences on productivity.Integrated soil fertility management(ISFM) is an approach to improve crop yields,while preserving sustainable and long-term soil fertility through the combined judicious use of fertilizers,recycled organic resources,responsive crop varieties,and improved agronomic practices,which minimize nutrient losses and improve the nutrient-use efficiency of crops.Soil fertility and nutrient management studies in Ethiopia under on-station and on-farm conditions showed that the combined application of inorganic and organic fertilizers significantly increased crop yields compared to either alone in tropical agro-ecosystems.Yield benefits were more apparent when fertilizer application was accompanied by crop rotation,green manuring,or crop residue management.The combination of manure and NP fertilizer could increase wheat and faba bean grain yields by 50%–100%,whereas crop rotation with grain legumes could increase cereal grain yields by up to 200%.Although organic residues are key inputs for soil fertility management,about 85% of these residues is used for livestock feed and energy;thus,there is a need for increasing crop biomass.The main incentive for farmers to adopt ISFM practices is economic benefits.The success of ISFM also depends on research and development institutions to provide technical support,technology adoption,information dissemination,and creation of market incentives for farmers in tropical agro-ecosystems.     

Optimizing nutrient availability and potential carbon sequestration in an agroecosystem

The uniformity, low cost and ease of application associated with inorganic fertilizers have diminished the use of organic nutrient sources. Concern for food safety, the environment and the need to dispose of animal and municipal wastes have focused attention on organic sources of N such as animal-derived amendments, green manures, and crop rotations. Managing organic N sources to provide sufficient N for crop growth requires knowledge of C and N decomposition over several years, particularly where manure and compost are applied. We report a comparison of compost and chemical fertilizer, use of a corn-corn-soybean-wheat rotation compared to continuous corn and the use of cover crops. Nitrogen (150 d) and C incubations (317 d) were conducted to determine the effect of cropping system and nutrient management on: N mineralization potential (NMP), the mineralizable organic N pool (N_o), the mean residence time (MRT) of No, C mineralization (C_min), and soil organic carbon (SOC) pool sizes and fluxes. Compost applications over 6 y increased the resistant pool of C by 30% and the slow pool of C by 10%. The compost treatment contained 14% greater soil organic C than the fertilizer management. Nitrogen was limiting on all compost treatments with the exception of first year corn following wheat fallow and clover cover crop. The clover cover crop and wheat-fallow increased inorganic N in both nutrient managements. We recommend that growers adjust their N fertilizer recommendation to reflect the quantity and timing of N mineralized from organic N sources and the N immobilization that can be associated with compost or other residue applications. Proper management of nutrients from compost, cover crops and rotations can maintain soil fertility and increase C sequestration.     

Tillage effects on microbial biomass and nutrient distribution in soils under rain-fed corn production in central-western Mexico

Quantifying how tillage systems affect soil microbial biomass and nutrient cycling by manipulating crop residue placement is important for understanding how production systems can be managed to sustain long-term soil productivity. Our objective was to characterize soil microbial biomass, potential N mineralization and nutrient distribution in soils (Vertisols, Andisols, and Alfisols) under rain-fed corn (Zea mays L.) production from four mid-term (6 years) tillage experiments located in central-western, Mexico. Treatments were three tillage systems: conventional tillage (CT), minimum tillage (MT) and no tillage (NT). Soil was collected at four locations (Casas Blancas, Morelia, Apatzingán and Tepatitlán) before corn planting, at depths of 0–50, 50–100 and 100–150 mm. Conservation tillage treatments (MT and NT) significantly increased crop residue accumulation on the soil surface. Soil organic C, microbial biomass C and N, potential N mineralization, total N, and extractable P were highest in the surface layer of NT and decreased with depth. Soil organic C, microbial biomass C and N, total N and extractable P of plowed soil were generally more evenly distributed throughout the 0–150 mm depth. Potential N mineralization was closely associated with organic C and microbial biomass. Higher levels of soil organic C, microbial biomass C and N, potential N mineralization, total N, and extractable P were directly related to surface accumulation of crop residues promoted by conservation tillage management. Quality and productivity of soils could be maintained or improved with the use of conservation tillage.     

Fertilizer Use and Wheat Yield in Central and Eastern European Countries from 1986 to 2005 and Its Implication for Developing Sustainable Fertilizer Management Practices

Economic and political challenges impact agricultural practices, production efficiency, and crop yields. We hypothesize that increased conversion efficiency of fertilizer to crop yield resulted from changes in fertilizer management in Central and Eastern European countries. Efficient nutrient management depends on fertilizer applied, management practices, and weather, which impact uptake, utilization efficiency, and crop yield. Trends in fertilizer consumption and wheat yields from 1986 to 2005 were studied for five countries. There were significant differences in yield gap, defined as the difference between potential and actual yields. Partial factor productivity of applied nitrogen fertilizer (N) is calculated from real and modified indices. A predictive metric is introduced based on the quantity of unworked, or nonproductive, N (N_uw). Sustainable cropping practices reduce N_uw and yield gap. Improved knowledge of crop responses to balanced plant nutrition at the country level contribute to improved agricultural and environmental policies and enhance production sustainability.     

Bioresource Nutrient Recycling and Its Relationship with Biofertility Indicators of Soil Health and Nutrient Dynamics in Rice–Wheat Cropping System

A field experiment was conducted for 3 years during 2006–2009 in India to study the effects of plant nutrient recycling through crop residue management, green manuring, and fertility levels on yield attributes, crop productivity, nutrient uptake, and biofertility indicators of soil health in a rice–wheat cropping system. The study revealed that soil microbial biomass carbon (SMBC) and carbon dioxide (CO₂) evolution were significantly greatest under crop residue incorporation (CRI) + Sesbania green manuring (SGM) treatment and were found at levels of 364 μg g^?1 soil and 1.75 μg g^?1 soil h^?1, respectively; these were increased significantly by recycling of organic residues. Activities of dehydrogenase and phosphatase enzymes increased significantly after 3 years, with maximum activity under CRI + SGM treatment. The CRI with or without SGM significantly influenced the plant height, number of tillers m^?2, number of grains panicle^?1 or ear^?1, and 1000-grain weight. Mean yield data of rice and wheat revealed that CRI or crop residue burning (CRB) resulted in slightly greater yield over crop residue removal (CRR) treatment. The CRI + SGM treatment again observed significantly greatest grain yields of 7.54 and 5.84 t ha^?1 and straw yields of 8.42 and 6.36 t ha^?1 in rice and wheat, respectively, over other crop residue management treatments. Total nitrogen (N), phosphorus (P) and potassium (K) uptake in rice–wheat system was greatest with amounts of 206.7, 37.2, and 205.6 kg ha^?1, respectively, in CRI + SGM treatment. Fertility levels significantly influenced the rice and wheat yield with greatest grain yields of 6.66 and 5.68 t ha^?1 and straw yields of 7.94 and 5.89 t ha^?1 in rice and wheat, respectively, with the application of 150% of recommended NPK. Total NPK uptake in rice–wheat system also increased significantly with increase in fertility levels with greatest magnitude by supplying 150% of recommended NPK. Overall, nutrient recycling through incorporation of crop residues and Sesbania green manuring along with inorganics greatly improved the crop productivity, nutrient uptake, and biofertility indicators of soil health with substantial influence on SMBC, CO₂ evolution, and dehydrogenase and phosphatase enzyme activities. This indicates that crop residue management along with Sesbania green manuring practice could be a better option for nutrient recycling to sustain the crop productivity and soil health in intensive rice–wheat cropping system in India as well as in similar global agroecological situations, especially in China, Pakistan, and Bangladesh.     

Three decades of soil microbial biomass studies in Brazilian ecosystems: Lessons learned about soil quality and indications for improving sustainability

Soil microbial biomass plays important roles in nutrient cycling, plant-pathogen suppression, decomposition of residues and degradation of pollutants; therefore, it is often regarded as a good indicator of soil quality. We reviewed more than a hundred studies in which microbial biomass-C (MB-C), microbial quotient (MB-C/TSOC, total soil organic carbon) and metabolic quotient (qCO₂) were evaluated with the objective of understanding MB-C responses to various soil-management practices in Brazilian ecosystems. These practices included tillage systems, crop rotations, pastures, organic farming, inputs of industrial residues and urban sewage sludge, applications of agrochemicals and burning. With a meta-analysis of 233 data points, we confirmed the benefits of no-tillage in preserving MB-C and reducing qCO₂ in comparison to conventional tillage. A large number of studies described increases in MB-C and MB-C/TSOC due to permanent organic farming, also benefits from crop rotations particularly with several species involved, whereas application of agrochemicals and burning severely disturbed soil microbial communities. The MB-C decreased in overgrazed pastures, but increased in pastures rotated with well-managed crops. Responses of MB-C, MB-C/TSOC and qCO₂ to amendment with organic industrial residues varied with residue type, dose applied and soil texture. In conclusion, MB-C and related parameters were, indeed, useful indicators of soil quality in various Brazilian ecosystems. However, direct relationships between MB-C and nutrient-cycling dynamics, microbial diversity and functionality are still unclear. Further studies are needed to develop strategies to maximize beneficial effects of microbial communities on soil fertility and crop productivity.     

Switchgrass Influences on Soil Biogeochemical Processes in the Dryland Region of the Pacific Northwest

Switchgrass and other perennial grasses have been promoted as biomass crops for production of renewable fuels. The objective of this study was to evaluate the effect of biomass removal on soil biogeochemical processes. A 3-year field study consisting of three levels of net primary productivity (NPP; low, medium, and high growing season precipitation) and two biomass crops (winter wheat and switchgrass) was conducted near Pendleton, Oregon. Switchgrass increased soil carbon (C)–nitrogen (N) ratio, but the effect varied with net primary productivity (NPP) and soil depth. In situ soil respiration (carbon dioxide; CO₂) rate from switchgrass increased with NPP level but switchgrass had greater cumulative flux than wheat in medium and low NPP. Nitrogen mineralization and microbial biomass carbon were significantly greater under switchgrass than under wheat at high and medium NPP. Introduction of switchgrass initiates major changes in soil nutrient dynamics through organic-matter input.     

Effect of long-term chemical and organic fertilization on rice productivity,nutrient use-efficiency,and balance under a rice-fallow-rice system

Nutrient sources and management influence soil properties and crop productivity indicating that sustained crop production needs nutrient rate specific tuning after certain periods of time. We hypothesize that long-term use of organic and inorganic nutrient sources maintains soil fertility and improve crop production. Yield and nutrient use efficiencies have not been evaluated in Bangladesh from long-term fertilizer trials focusing on adaptation strategies for sustained food production. So, the objectives of the present investigation were to examine the effects of organic and inorganic amendments on yields and soil properties under a rice-fallow-rice system. The experiment was initiated in 1985 with 12 treatments under dry season irrigated rice culture at the Bangladesh Rice Research Institute, Gazipur. The effects of organic and inorganic nutrient sources were evaluated under missing element techniques. The contributions of nitrogen (N), phosphorus (P), and potassium (K) fertilizers to yields were more in the dry season but the role of P was negligible in the wet season. The omissions of N, P and K nutrients are not suitable management option for rice cultivation during dry and wet seasons, although P can be omitted in the wet season provided its full dose is applied in the dry season. The combined use of organic and inorganic nutrient sources are the best option for improving rice productivity and sustaining soil fertility in a rice-fallow-rice system in Bangladesh.     

The short-term cover crops increase soil labile organic carbon in southeastern Australia

Little information is available about the effects of cover crops on soil labile organic carbon (C), especially in Australia. In this study, two cover crop species, i.e., wheat and Saia oat, were broadcast-seeded in May 2009 and then crop biomass was crimp-rolled onto the soil surface at anthesis in October 2009 in southeastern Australia. Soil and crop residue samples were taken in December 2009 to investigate the short-term effects of cover crops on soil pH, moisture, NH₄⁺–N, NO₃⁻–N, soluble organic C and nitrogen (N), total organic C and N, and C mineralization in comparison with a nil-crop control (CK). The soil is a Chromic Luvisol according to the FAO classification with 48.4 ± 2.2% sand, 19.5 ± 2.1% silt, and 32.1 ± 2.1% clay. An exponential model fitting was employed to assess soil potentially labile organic C (C ₀) and easily decomposable organic C for all treatments based on 46-day incubations. The results showed that crop residue biomass significantly decreased over the course of 2-month decomposition. The cover crop treatments had significantly higher soil pH, soluble organic C and N, cumulative CO₂–C, C ₀, and easily decomposable organic C, but significantly lower NO₃⁻–N than the CK. However, no significant differences were found in soil moisture, NH₄⁺–N, and total organic C and N contents among the treatments. Our results indicated that the short-term cover crops increased soil labile organic C pools, which might have implications for local agricultural ecosystem managements in this region.     

氮肥运筹对稻茬小麦土壤硝态氮含量时空分布和氮素利用的影响

研究了不同氮肥运筹对土壤硝态氮时空分布及小麦氮肥利用效率的影响。结果表明,小麦氮素利用效率随施氮量的增加而显著降低,增加追肥比例提高了产量和氮肥利用效率,品种间趋势一致。0～60 cm土层土壤硝态氮含量冬前最高,随着生育进程而逐渐降低。随施氮量增加土壤硝态氮含量升高,特别是下层土壤硝态氮含量在施氮处理下更为明显。从播种至成熟,不施氮处理土壤氮素出现了表观亏缺,施氮处理均表现氮素盈余,且随施氮量的增加而增加。因此,在小麦生产中应避免在播种时一次性大量施用氮肥,而分期施肥有利于小麦吸收利用,并且可以减少深层土壤硝态氮的累积。     

Productivity and nutrient use efficiency of maize,sorghum, and cotton in the West African Dry Savanna

Sustainable agricultural practices are needed to improve food security and support livelihoods in West Africa, where soil nutrient deficiencies and rainfed production systems prevail. The objective of this study was to assess the productivity and nitrogen (N) and phosphorus (P) use efficiencies of three dominant crops (maize, sorghum, and cotton) under different soil management strategies in the dry savanna of northern Benin. Data were collected for each crop in experiments with (1) an un‐amended soil as control, (2) a low use of external inputs, (3) an integrated soil–crop management practice, and (4) a high mineral fertilizer use, as treatments. Data were collected through researcher‐managed and farmer‐managed on‐farm trials in 2014 and 2015, and analyzed using linear robust mixed effects model and Pearson's correlation. Above‐ground biomass accumulation did not differ significantly among the control, integrated soil–crop management practice, and high mineral fertilizer use up to 30, 50, and 60 d after planting for maize, cotton, and sorghum, respectively. Thereafter, the differences in growth were substantial for each crop with highest biomass monitored with high mineral fertilizer use and lowest with the control. Biomass and economic yields at harvest were highest under high mineral fertilizer use and integrated soil–crop management practice, although the magnitude was crop‐specific. With the integrated soil–crop management practice and high mineral fertilizer use, N and P uptake by all crops was higher than for the un‐amended soil conditions. Inter‐seasonal changes in N uptake were higher for sorghum and cotton, but lower for maize. The highest agronomic efficiency and apparent recovery of N and P as well as positive N and P partial balances were obtained with the integrated soil–crop management practice for all three crops tested. The integrated soil–crop management strategy gave the highest yields and significantly improved N and P use efficiencies. The findings can contribute to formulating site and crop‐specific recommendations for sustainable agricultural practices in the Dry Savanna zone of West Africa.     

Nitrogen Use Efficiency in an 11-Year Study of Conventional and Organic Wheat Cultivation

Abstract

Resource conservation with respect to nitrogen (N) was compared in organic and conventional cultivation of winter and spring wheat. Sustainability was measured in the nitrogen use efficiency of plant‐available N. The amounts of N entering each system and the amounts removed in the harvested crop and remaining as unused mineral nitrogen in the soil at harvest were determined. Net surpluses and losses during the growing season were also monitored, and the environmental variables influencing N harvest in the different cultivation systems were identified. The study was carried out in three different cultivation systems: conventional animal production (CONV), organic animal production (ORG1), and organic cereal production (ORG2). On average for all years and sampling occasions in winter wheat, there were approximately 60 kg more mineral nitrogen left in the soil during the growing season in CONV than in ORG1, and coefficients of variation were higher in CONV. The maximum values were considerably higher in CONV than in ORG1 (p=0.06–0.09), which increased the risk of leaching in the former, particularly in winter wheat cultivation. Nitrogen use efficiency in winter and spring wheat cultivation was 74% in whole crop conventional winter wheat and 81% in organic. Nitrogen use efficiency in harvested winter wheat grain was 44% for CONV and 49% for ORG1. ORG1 spring wheat was as efficient as ORG1 winter wheat, whereas ORG2 spring wheat used 73% of N in the whole crop and 39% in grain. Multivariate regression analysis showed that climate affected CONV and ORG1 winter wheat differently. High temperature in May increased grain yields in ORG1, but the converse was true for CONV. Large unused mineral N reserves at harvest coincided with large N harvest in CONV winter wheat. Residual fertility effects from the preceding crop produced high yields in ORG1 winter and spring wheat but had no effect in CONV. Generally, an increase in N reserves between plant development stages 13 and 31 was positive for both CONV and ORG1 winter wheat. Both winter and spring wheat require most N during this period, so the potential for improvement seems to lie in increasing mineralization (e.g., by intensified weed harrowing early in stage 13 in winter wheat and between stages 13 and 31 in spring wheat). Cultivation of winter wheat in ORG1 was a more efficient use of nitrogen resources than CONV. CONV efficiency could be improved by precision fertilization on each individual field with the help of N analysis before spring tillage and sensor‐controlled fertilization.     

Effect of Integrated Nutrition in Aromatic Rice on Carbon and Nutrient Status in an Inceptisol

Inorganic fertilizer-based nutrient management is the maintenance of soil fertility for sustaining increased crop productivity, but often at the cost of degrading soil health. This study was conducted to determine whether incorporation of organics in the conventional inorganic-based nutrient management practice on aromatic rice could sustain both fertility and soil organic carbon status on a silt loam Aeric Haplaquept. Addition of organic manure along with inorganic fertilizer could almost maintain organic carbon status of soil, while the treatment only with inorganic fertilizer registered a substantial decrease (6.58%) from its initial value. Among the treatment combinations, the treatment receiving 1 t ha^?1 mustard cake and inorganic fertilizer @ N₄₀P₂₀K₂₀ was the best, which registered the highest grain (3.01 t ha^?1) and straw (5.32 t ha^?1) yield of rice, highest nutrient uptake, and least decline in available N, P, and K status of soil. However, even the best treatment combination also was proved to be suboptimal in sustaining soil fertility.     

不同产量水平旱地冬小麦品种的氮磷利用差异分析

以9个旱地冬小麦品种为材料,通过田间试验研究不同产量水平旱地冬小麦品种氮、磷效率的差异。结果表明,不同冬小麦品种的籽粒和地上部吸氮量、吸磷量、氮磷收获指数、氮磷效率均存在明显差异。随养分投入水平的提高,不同产量水平品种的籽粒和地上部吸氮量、吸磷量均提高,高产品种随养分投入增加而提高的敏感程度高于中产和低产品种。氮磷收获指数随养分投入水平的提高没有明显的变化规律。低养分投入水平下,高产品种的氮肥回收率和偏生产力分别较低产品种高222%和49%;磷肥回收率和偏生产力分别较低产品种高766% 和49%,高投入降低了各产量水平品种的偏生产力。     

Assessing Nitrogen Fertilization Strategies in Winter Wheat and Cotton Crops in Northern Greece

The management of fertilizer application is crucial for agricultural production and environmental safety.The objective of this study was to assess the effciency of different fertilization strategies,applying fertilizers with and without nitrification inhibitors(NIs) in split application,in Greece.The assessment criteria used were based on crop yield,soil nitrogen(N)concentrations and economic effciency.For this purpose two crops(winter wheat and cotton)were seffected in order to explore the optimum fertilization strategy for each crop.Three treatments combining fertilizers with NIs were tested compared with conventional fertilization(CF).Slight differences in the quantity and the combination of fertilizers with NIs applied resulted in variable effects on crop yield,soil N and economic return.Split N application of 102 kg ha^-1,with half of the total amount applied at seeding,resulted in higher grain yield of winter wheat,lower NO₃^--N in soil and higher economic return.This result reveals the importance of N application at seeding in wheat crop.Fertilization strategy with 109.5 kg N ha^-1 and split P application resulted in higher cotton yield and higher economic profit.Split P application seemed to increase yield,even though it is not a common practise in the area.     

耕作和保墒措施对冬小麦生育时期光合特征及水分利用的影响

为探明不同耕作保墒措施下冬小麦生育期间光合生理特征及其增产机理,采用田间试验,以常规耕作为对照,采用深松、秸秆覆盖、免耕、施用有机肥及保水剂等措施,研究了不同耕作和保墒措施对冬小麦生育期间光合作用、产量及水分利用效率的影响。结果表明:冬小麦光合速率和叶片水分利用效率均以孕穗期最高,而灌浆期最低。蒸腾速率和气孔导度均以扬花期最高。对不同处理而言,在各生育时期均以深松处理的光合速率和叶片水分利用效率最高,其次为秸秆覆盖处理。在拔节期、孕穗期和扬花期以有机肥处理的蒸腾速率最高,而灌浆期以秸秆覆盖的蒸腾速率较高,在全生育期对照的蒸腾速率均较低。气孔导度与蒸腾速率表现规律基本一致。不同耕作、保墒措施均提高了小麦的穗数、穗粒数及千粒重,以及小麦籽粒产量和水分生产效率,降低了小麦总耗水量;各处理中以深松处理的效果最佳,其产量和水分生产效率分别较对照提高19.6%和38.3%。相关分析表明:各时期的小麦光合速率及叶片水分利用效率均与小麦产量和水分生产效率呈正相关,且随生育期的推进,其相关性增强,特别在扬花期,光合速率对于小麦产量和水分生产效率的影响更显著。     

CO2浓度升高、氮和水分对春小麦养分吸收和土壤养分的效应

研究了 2种CO2浓度水平 ,2种土壤水分处理和 5种N肥施用水平对春小麦 (TriticumaestivumL cv DingxiNo. 8654)养分吸收和土壤速效养分的影响。结果表明 ,高CO2浓度 (700 molmol-1)明显降低春小麦对氮(N)的吸收 ,低N时降低更为明显 ,但对磷 (P)、钾 (K)吸收的影响不明显。小麦对N、P、K吸收 ,干旱处理明显比湿润处理低。CO2浓度增高对土壤速效N的影响与土壤水分状况有关。湿润处理 ,CO2浓度增加的处理速效N量比当前CO2浓度的处理低 ;而干旱处理 ,施N 50、100、150mgkg-1时 ,速效N则较高。高CO2 浓度对土壤速效P、K量的影响不明显 ,而低N和水分不足 ,土壤速效P、K量较高     

Dynamics of soil extractable carbon and nitrogen under different cover crop residues

Purpose

Cover crop residue is generally applied to improve soil quality and crop productivity. Improved understanding of dynamics of soil extractable organic carbon (EOC) and nitrogen (EON) under cover crops is useful for developing effective agronomic management and nitrogen (N) fertilization strategies.

Materials and methods

Dynamics of soil extractable inorganic and organic carbon (C) and N pools were investigated under six cover crop treatments, which included two legume crops (capello woolly pod vetch and field pea), three non-legume crops (wheat, Saia oat and Indian mustard), and a nil-crop control (CK) in southeastern Australia. Cover crops at anthesis were crimp-rolled onto the soil surface in October 2009. Soil and crop residue samples were taken over the periods October?CDecember (2009) and March?CMay (2010), respectively, to examine remaining crop residue biomass, soil NH₄ ⁺?N and NO₃ ^??CN as well as EOC and EON concentrations using extraction methods of 2?M KCl and hot water. Additionally, soil net N mineralization rates were measured for soil samples collected in May 2010.

Results and discussion

The CK treatment had the highest soil inorganic N (NH₄ ⁺?N?+?NO₃ ^??CN) at the sampling time in December 2009 but decreased greatly with sampling time. The cover crop treatments had greater soil EOC and EON concentrations than the CK treatment. However, no significant differences in soil NH₄ ⁺?N, NO₃ ^??CN, EOC, EON, and ratios of EOC to EON were found between the legume and non-legume cover crop treatments across the sampling times, which were supported by the similar results of soil net N mineralization rates among the treatments. Stepwise multiple regression analyses indicated that soil EOC in the hot water extracts was mainly affected by soil total C (R ²?=?0.654, P?<?0.001), while the crop residue biomass determined soil EON in the hot water extracts (R ²?=?0.591, P?<?0.001).

Conclusions

The cover crop treatments had lower loss of soil inorganic N compared with the CK treatment across the sampling times. The legume and non-legume cover crop treatments did not significantly differ in soil EOC and EON pools across the sampling times. In addition, the decomposition of cover crop residues had more influence on soil EON than the decomposition of soil organic matter (SOM), which indicated less N fertilization under cover crop residues. On the other hand, the decomposition of SOM exerted more influence on soil EOC across the sampling times among the treatments, implying different C and N cycling under cover crops.     

Compost,Manure and Synthetic Fertilizer Influences Crop Yields,Soil Properties,Nitrate Leaching and Crop Nutrient Content

From 1993 to 2001, a maize-vegetable-wheat rotation was compared using either 1) composts, 2) manure, or 3) synthetic fertilizer for nitrogen nutrient input. From 1993 to 1998, red clover (Trifolium pratense L.) and crimson clover (Trifolium incarnatum L.) were used as an annual winter legume cover crop prior to maize production. From 1999 to 2001, hairy vetch (Vicia villosa Roth.) served as the legume green manure nitrogen (N) source for maize. In this rotation, wheat depended entirely on residual N that remained in the soil after maize and vegetable (pepper and potato) production. Vegetables received either compost, manure, or fertilizer N inputs. Raw dairy manure stimulated the highest overall maize yields of 7,395 kg/ha (approximately 140 bushels per acre). This exceeded the Berks County mean yield of about 107 bushels per acre from 1994 to 2001. When hairy vetch replaced clover as the winter green manure cover crop, maize yields rose in three of the four treatments (approximately 500-1,300 kg/ha, or 10-24 bu/a). Hairy vetch cover cropping also resulted in a 9-25 % increase in wheat yields in the compost treatments compared to clover cover cropping. Hairy vetch cover crops increased both maize and wheat grain protein contents about 16 to 20% compared to the clover cover crop. Compost was superior to conventional synthetic fertilizer and raw dairy manure in 1) building soil nutrient levels, 2) providing residual nutrient support to wheat production, and 3) reducing nutrient losses to ground and surface waters. After 9 years, soil carbon (C) and soil N remained unchanged or declined slightly in the synthetic fertilizer treatment, but increased with use of compost amendments by 16-27% for C and by 13-16% for N. However, with hairy vetch cover crops, N leaching increased 4 times when compared to clover cover crops. September was the highest month for nitrate leaching, combining high rainfall with a lack of active cash crop or cover crop growth to use residual N. Broiler litter leaf compost (BLLC) showed the lowest nitrate leaching of all the nutrient amendments tested (P= 0.05).