Soil-Test-Based Optimum Fertilizer Doses for Attaining Yield Targets of Rice under Midland Alfisols of Eastern India

Soil-test crop-response experiments on rice were conducted in the Bastar Plateau Agroclimatic Zone of Chhattisgarh during 2009–2011 to assess yield, soil, plant, and fertilizer nitrogen (N), phosphorus (P), and potassium (K) nutrient relationships and calibrate optimum fertilizer doses for attaining yield targets. Soil fertility status was poor to medium for N (194–283 kg ha^?1) and P (7.53–19.66 kg ha^?1), and medium to good for K (226–320 kg ha^?1). Based on nutrient requirements (NR, kg q^?1) and contributions from soil (CS, %), fertilizer (CF, %), and farmyard manure (CFYM, %), optimum fertilizer doses were derived. The fertilizer doses were validated for attaining yield targets of 5000 and 6000 kg ha^?1 in farmer’s fields. Rice yield within 10% deviation was attained, which indicated that soil-test-based fertilizer dose was superior. This approach could be adopted for regions with similar soil and agroclimatic conditions in other parts of the world to increase rice yields.     

Modeling of Soil-Plant-Fertilizer Relationships for Optimizing Fertilizer Doses for Different Levels of Finger Millet Yield under Semi-Arid Alfisols

Experiments were conducted to test the superiority of treatment combinations of nitrogen (N; 0, 50, 100, 150, 200 kg ha^?1), phosphorus (0, 30, 60, 90 kg ha^?1) and potassium (0, 30, 60 kg ha^?1) for finger millet during 2005–2007. Application of 200-90-60 kg ha^?1 gave maximum yield of 1666, 1426 and 1640 kg ha^?1 in 3 years, respectively. The yield regression model through soil and fertilizer nutrients gave predictability of 0.98, 0.97 and 0.98, with sustainability yield index (SYI) of 50.4, 49.4 and 52.5 in 2005, 2006 and 2007, respectively. Optimum nitrogen, phosphorus and potassium (NPK) doses for attaining yields of 800 and 1200 kg ha^?1 were derived at soil nitrogen, phosphorus and potassium of 75–400, 10–70 and 150–750 kg ha^?1. Fertilizer nitrogen, phosphorus and potassium ranged from 30–128, 3–19, 13–25 kg ha^?1 and 105–203, 4–32, 27–39 kg ha^?1 for attaining 800 and 1200 kg ha^?1 yield, respectively. The doses could be adopted for attaining sustainable yields under semiarid Alfisols.     

System productivity,nutrient use efficiency and apparent nutrient balance in rice-based cropping systems

A 2-year field experiment was conducted to assess system productivity, nutrient use efficiency and apparent balances of phosphorus (P) and potassium (K) in diversified rice-based cropping systems at Gazipur, Bangladesh. Four cropping systems: wheat–fallow–rice, maize–fallow–rice, potato–fallow–rice and mustard–fallow–rice in main plots and four nutrient combinations: NPK, NK, NP and PK in sub-plots were arranged in a split-plot design with three replications. Receiving the NPK treatment, all the component crops gave the highest yield, and omission of N from fertilizer package gave the lowest yield. The maize–rice system removed the highest amount of N (217 kg ha^?1), P (41 kg ha^?1) and K (227 kg ha^?1) followed by wheat–rice, potato–rice and the least in mustard–rice system. The wheat–rice and maize–rice system showed negative K balance of –35.5 and –60.4 kg ha^?1 in NPK treatment, while potato–rice system showed a positive K balance of 31.0 kg ha^–1 with NPK treatment. The N, P and K uptake and apparent recovery by the test crops may be used for site-specific nutrient management. The K rates for fertilizer recommendation in wheat and maize in Indo-Gangetic plain need to be revised to take account for the negative K balance in soil.     

Macro-Nutrient Concentration and Content of Irrigated Soybean Grown in the Early Production System of the Midsouth

Macro-nutrients in soybean (Glycine max L. Merr.) have not been extensively researched recently. Concentrations and contents of nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur (N, P, K, Ca, Mg, and S) were determined for three irrigated cultivars grown using the early soybean production system (ESPS) on two soils (a sandy loam and a clay) in the Mississippi Delta during 2011 and 2012. Data were collected at growth stages V3, R2, R4, R6, and R8. No change in macro-nutrients due to soil type or years occurred and modern cultivars were similar to data collected >50 years ago. Mean seed yield of 3328 kg ha^?1 removed 194.7 kg N ha^?1, 16.5 kg P ha^?1, 86.0 kg K ha^?1, 17.5 kg Ca ha^?1, 9.0 kg Mg ha^?1, and 10.4 kg S ha^?1. Increased yields over the decades are likely due to changed plant architecture and/or pests resistance, improved cultural practices, chemical weed control, and increased levels of atmospheric carbon dioxide (CO₂). Yield improvements by genetically manipulating nutrient uptake appear to be unlikely.     

Changes in Tomato Fruit Quality and Antioxidant Enzyme Activities under Deficit Irrigation and Fertilizer Application in a Solar Greenhouse in Northwest China

The interaction between water availability in the soil and fertilizer application rates often strongly affects crop growth. In the current study, the quality of fresh fruit and antioxidant enzymes of tomato crops (Lycopersicon esculentum Mill) were investigated under different irrigation (low water content [W_l]: 50 ~ 60% field moisture capacity (FMC); moderate [W_m]: 70 ~ 80% FMC; and high [W_h]: 90 ~ 100% FMC) and fertilizer conditions (deficit fertilizer [F_l]: 195 kg ha^?1 nitrogen (N) + 47 kg ha^?1 phosphorus pentoxide (P₂O₅) and moderate [F_m]: 278 kg ha^?1 N + 67 kg ha^?1 P₂O₅) in a solar greenhouse. The results showed that the quality of fresh fruits and the antioxidant enzyme activities in the leaves and fruits were related to the water content in the soil. Deficit irrigation improved the fruit quality and 50 ~ 60% FMC combined with fertilizer application rates of 195 kg ha^?1 N + 47 kg ha^?1 P₂O₅ is recommended for tomato crop cultivation under greenhouse conditions.     

Estimation of Optimum Nitrogen Fertilizer Rates in Winter Wheat in Humid Mediterranean Conditions,II: Economically Optimal Dose of Nitrogen

Cereal grain and nitrogen (N) fertilizer prices have varied greatly in recent years. The aim of this study was to determine the optimum dose of N fertilizer needed to maximize revenues of soft red winter wheat in Alava (northern Spain). Economically optimum rates of N application (N_yield) ranged from 142 to 174 kg N ha^?1 depending on the price of both N fertilizer and wheat. Growers received an extra income of 0.006 [euro] kg^?1 if the grain protein content was greater than 12.5%, with the minimum required N dose to obtain this value (N_prot) being 176 kg ha^?1. The extra amount of N fertilizer required over N_yield to reach N_prot ranged from 2 to 34 kg N ha^?1, and the extra benefits associated varied from 24 to 36 [euro] ha^?1.     

Mitigation options for N2O emission from a corn field in Kalimantan,Indonesia

Abstract

Field experiments were designed to quantify N₂O emissions from corn fields after the application of different types of nitrogen fertilizers. Plots were established in South Kalimantan, Indonesia, and given either urea (200 kg ha^?1), urea (170 kg ha^?1) + dicyandiamide ([DCD] 20 kg ha^?1) or controlled-release fertilizer LP-30 (214 kg ha^?1) prior to the plantation of corn seeds (variety BISI 2). Each fertilizer treatment was equivalent to 90 kg N ha^?1. Plots without chemical N fertilizer were also prepared as a control. The field was designed to have three replicates for each treatment with a randomized block design. Nitrous oxide fluxes were measured at 4, 8, 12, 21, 31, 41, 51, 72 and 92 days after fertilizer application (DAFA). Total N₂O emission was the highest from the urea plots, followed by the LP-30 plots. The emissions from the urea + DCD plots did not differ from those from the control plots. The N₂O emission from the urea + DCD plots was approximately one thirtieth of that from the urea treatment. However, fertilizer type had no effect on grain yield. Thus, the use of urea + DCD is considered to be the best mitigation option among the tested fertilizer applications for N₂O emission from corn fields in Kalimantan, Indonesia.     

Optimizing water,nitrogen and crop density in canola cultivation using response surface methodology and central composite design

Abstract

Optimisation of water and nitrogen use is an effective management tool to conserve resources and reduce environmental pollutions. Response surface methodology (RSM) is defined as a collection of mathematical and statistical methods that are used to develop, to improve or to optimize a product or process. In order to determine optimum levels of water, nitrogen and planting density of canola (Brassica napus L.), a 2-year experiment (2010–2011) was carried out by central composite design as RSM at the research station of Ferdowsi University of Mashhad. The treatments were designed based on low and high levels of irrigation (1500 and 4000 m³ ha^?1), nitrogen (0 and 400 kg N ha^?1) and density (50 and 150 plant m^?2) as independent variables. Furthermore, seed yield, nitrogen losses, nitrogen use efficiency (NUE) and water use efficiency (WUE) were measured as response variables in a full quadratic polynomial model. Optimum levels of irrigation, nitrogen and planting density were suggested to achieve the target range of dependent variables based on three scenarios: economic, environmental and eco-environmental. The results showed that increasing irrigation and fertilizer led to an increase in seed yield and nitrogen losses, whereas increasing canola density resulted in an increase in seed yield but a decrease in nitrogen losses. The optimum levels of water, fertilizer and density based on environmental scenario were 1802 m³ ha^?1, 11 kg N ha^?1 and 122 plant m^?2, respectively. To achieve optimum conditions under the economic scenario, it is necessary to use 3411 m³ water ha^?1, 178 kg N ha^?1 and 119 plant m^?2. Amounts of 2347 m³ water ha^?1, 92 kg N ha^?1 and 114 plant m^?2 were found to be the optimum conditions for the eco-environmental scenario. In general, it seems that resource use based on the eco-environmental scenario may be the most favorable cropping strategy for canola production.     

Estimation of Ammonia Volatilization from a Paddy Field after Application of Controlled-Release Urea Based on the Modified Jayaweera–Mikkelsen Model Combined with the Sherlock–Goh Model

The continuous airflow enclosures with an acid trap method was widely used to investigate ammonia (NH₃) volatilization in field; however, it could be time-consuming for the estimation of NH₃ volatilization in field with the application of controlled-release urea (CRU) because NH₃ volatilization with CRU application could occur during the entire crop growth period. An NH₃ volatilization estimation method based on the modified Jayaweera–Mikkelsen (J-M) model combined with the Sherlock–Goh model was used to simulate NH₃ volatilization in a paddy field after 255 kg N ha^?1 as CRU (polymer-coated urea with the concentration of 43% nitrogen, 100% for basal) and urea (70% for basal, 30% for topdressing) during the rice growth period including flooded and non-flooded periods in Wuxi, China. Results indicated that NH₃ volatilization can be modeled with the proposed measure because no significant difference (P< 0.001) was observed between the simulated values and the observed values; the correlation coefficient (r²) was 0.615 for CRU and 0.840 for urea during the flooded period, and 0.991 for CRU and 0.946 for urea during the non-flooded period. Compared with urea, NH₃ volatilization was minimized by 43.2% with the application of CRU based on simulated value within the rice growth period, which was 40.40 kg N ha^?1 for CRU and 78.62 kg N ha^?1 for urea during the flooded period, and 5.52 kg N ha^?1 for CRU and 2.33 kg N ha^?1 for urea during the non-flooded period. Therefore, CRU could be a promising nitrogen fertilizer to prevent NH₃ losses in the rice paddies at the investigated area.     

Effect of Combined Use of Organic and Inorganic Sources of Nutrients on Sunflower Yield,Soil Fertility,and Overall Soil Quality in Rainfed Alfisol

Abstract

To study the response of inorganic and organic nitrogen (N) sources both alone and in conjunction and their influence on soil quality, a field experiment was conducted during kharif and rabi seasons using sunflower (MSFH‐8) as test crop. The experimental site soil was Typic Haplustalf situated at Hayatnagar Research Farm of Central Research Institute of Dryland Agriculture, Hyderabad, India, at 17° 18′ N latitude, 78° 36′ E longitude. The experiment design was a simple randomized block design with 11 treatments replicated four times. Among all the treatments, vermicompost (VC)+Fert at 25+25 kg N ha^?1 recorded the highest grain yields of 1878 and 2160 kg ha^?1 during both kharif and rabi seasons, respectively, which were 43.9 and 85.1% higher than their respective control plots. Apparent N recovery varied from as little as 38.30% (FYM at 50 kg N ha^?1) to 62.16 (25 kg N ha^?1) during kharif and 49.65 (75 kg ha^?1) to 83.28% (VC+Fert at 25+25 kg N ha^?1) during rabi season. Conjunctive nutrient treatments proved quite superior to other set of treatments in improving the uptake of N, phosphorus (P), potassium (K), sulfur (S), and micronutrients in sunflower and their buildup in the soil. Highest relative soil quality indexes (RSQI) were observed under VC+Fert at 25+25 kg N ha^?1 (1.00) followed by VC+Gly at 25+25 kg N ha^?1 (0.87). Considering the yield and relative soil quality indices (RSQI), conjunctive applications of VC with either inorganic fertilizer, FYM, or Gly at 25+25 kg N ha^?1 could be a successful and sustainable soil nutrient management practice in semi‐arid tropical Alfisols. Besides this, the fertilizer N demand could be reduced up to 50%.     

Effect of rates and sources of nitrogen on rice yield,nitrogen efficiency,and methane emission from irrigated rice cultivation

The agronomic benefits of manure application to increase rice production have been recognized, but the impact on global change has always been a controversial topic. This study was designed to determine the separate and combined effects of cattle manure (CM) and nitrogen (N) fertilizer on rice yield, N efficiency, and methane (CH₄) emissions from rice cultivation. A pot-scale experiment was conducted with four levels (0, 60, 120, and 180 kg ha^?1) of N from urea and two levels (120 and 180 kg ha^?1) of N from combination of urea and CM (Urea:CM = 60:60 and 60:120). Rice yield and physiological N efficiency were obtained using agronomic measurements. To determine the global warming potential (GWP) of each treatment, CH₄ emissions were measured throughout the rice-growing period. Grain yield (GY) was not significantly different between the treatments of 120 and 180 kg ha^?1 regardless of N source. However, both rates of CM treatments enhanced CH₄ emission and differences in GWP were significant. In conclusion, urea applied at 120 kg N ha^?1 was optimal for rice productivity and environmental impact (EI) despite CM played a crucial role in improving the N efficiency and total N in the soil after harvest.     

Water Use and Soil Fertility under Rice–Wheat Cropping System in Response to Green Manuring and Zinc Nutrition

ABSTRACT

Soil fertility and water use are two important aspects that influence rice productivity. This study was conducted to evaluate the performance of in-situ (sesbania and rice bean) and ex-situ (subabul) green manuring along with zinc fertilization on water productivity and soil fertility in rice under rice–wheat cropping system at Indian Agricultural Research Institute, New Delhi, India. Sesbania incorporation recorded higher total water productivity (2.20 and 3.24 kg ha^?1 mm^?1), available soil nutrients, organic carbon, alkaline phosphatase activity, microbial biomass carbon and increased soil dehydrogenase activity by 39.6 and 26.8% over subabul and rice bean respectively. Among interaction of green manures and zinc fertilization, subabul × foliar application of chelated zinc-ethylenediaminetetraacetic acid at 20, 40, 60 and 80 days after transplanting recorded highest total water productivity (2.56 and 3.79 kg ha^?1 mm^?1). Foliar application of chelated Zn-EDTA at 20, 40, 60 and 80 days after transplanting recorded significantly higher water productivity than other Zn treatments, however it was statistically similar with foliar application of zinc at active tillering + flowering + grain filling. Sesbania × 5 kg Zn ha^?1 through chelated Zn-EDTA, recorded highest available nitrogen, phosphorus, potassium, zinc, manganese, copper and iron than other green manure and Zn fertilization interactions, although it was statistically similar with rice bean × 5 kg Zn ha^?1 through chelated Zn-EDTA as soil application. Sesbania × foliar application of 5 kg Zn ha^?1 through chelated Zn-EDTA as soil application recorded highest soil enzymatic activities and microbial biomass carbon.     

Impact of land use on nitrogen concentration in groundwater and river water

Abstract

The aim of this study was to evaluate the impact of land use on nitrate nitrogen (NO₃-N) in shallow groundwater (G-N) and total nitrogen (N) in river water (R-N). The study area consisted of 26 watersheds (1342 km²) covering 72% of Kagawa Prefecture in Japan. We estimated G-N specific concentrations, which showed the magnitude of the upland fields, paddy fields, forests and urban land-use contributions to watershed-mean G-N. G-N specific concentrations were gained as partial regression coefficients using a multiple regression analysis of the watershed-mean G-N concentrations and the land-use ratios in each of the 26 watersheds. The results showed that the G-N specific concentration, which was gained as the partial regression coefficient for the multiple regression analysis, was 15.2 mg L^?1, 10.3 mg L^?1, 2.3 mg L^?1 and 2.5 mg L^?1 for the upland fields, paddy fields, forests and urban land-use types, respectively. R-N pollution load runoff to the river mouth was calculated by multiplying R-N specific concentration (previously reported) by river flow at the river mouth. Similarly, G-N pollution load arrival to groundwater was calculated by multiplying G-N specific concentration by the groundwater flow. The R-N pollution load runoff was 19.3 kg ha^?1 y^?1, 7.7 kg ha^?1 y^?1, 1.7 kg ha^?1 y^?1 and 7.6 kg ha^?1 y^?1, while the G-N pollution load arrival was 7.3 kg ha^?1 y^?1, 5.0 kg ha^?1 y^?1, 1.1 kg ha^?1 y^?1 and 1.2 kg ha^?1 y^?1, for upland fields, paddy fields, forests and urban areas, respectively. These results showed that the N in river water and groundwater was derived mainly from runoff and leaching from croplands. Therefore, the relationships between watershed-mean non-absorbed, applied nitrogen (NAA-N: nitrogen applied to cropland via fertilizer and manure without being absorbed by crops), R-N concentration and watershed-mean G-N concentration were investigated. A curvilinear correlation was observed between NAA-N and R-N concentrations (r² = 0.68) except for one small, high-density, urban watershed, and a weak linear correlation was observed between NAA-N and G-N concentrations (r² = 0.42).     

Effects of Nitrogen Application Rates on Rice Grain Yield,Nitrogen-Use Efficiency,and Water Quality in Paddy Field

Excessive nitrogen (N) fertilizer application is common in the central Zhejiang Province area, China. A three-year (2009–11) experiment was conducted to determine the optimum N application rate for this area by studying the effects of various N rates on rice (Oryza sativa L.) yield, N-use efficiency (NUE), and quality of paddy field water. Results showed that no significant yield differences were observed under N rates from 180 to 315 kg ha^?1. The NUE could be improved by reducing N application rates without significantly decreasing yield. Due to high ammonia (NH₄⁺-N) and nitrate (NO₃^—N) concentrations, 5–7 days after N application was a critical stage for reducing N pollution. The N rate for the greatest yield was 176 kg ha^?1, accounting for 65 percent of the conventional N rate (270 kg ha^?1). The N-rate reduction in this area may be necessary for maintaining high yield, improving NUE, and reducing environmental pollution.     

Effect of potassium fertilization on yield and potassium nutrition of Boro rice in a wetland ecosystem of Bangladesh

Effect of potassium (K) fertilization (0, 20, 40, 60, 80 and 100 kg K ha^?1) on yield, nitrogen (N) and K nutrition of Boro (dry season) rice and apparent soil K balance was studied. Experiment was conducted at Bangladesh Rice Research Institute (BRRI) regional station farm, Habiganj, Bangladesh during 2007–2008 to 2009–2010 in a wetland rice ecosystem under haor area. Cropping pattern was Boro–Fallow–Fallow. A popular rice variety BRRI dhan29 was tested in a randomized complete block design with three replications. Results indicated that BRRI dhan29 maintained an average grain yield of 5.19 t ha^?1 year^?1 without K fertilization. Potassium fertilization significantly increased the grain yield to 6.86 t ha^?1 year^?1. Quadratic equations best explained the progressive increase of rice yield with increasing K rates. Optimum dose of K in 3 years ranged from 78 to 93 kg ha^?1. Internal N use efficiency of rice decreased with increasing K rates. However, K use efficiency was inconsistent. Apparent K balance study revealed that application of 100 kg K ha^?1 was not able to maintain a positive K balance in soil under wetland ecosystem with Boro–Fallow–Fallow cropping system. However, K fertilization decreased the negativity of K balance in soil.     

Assessment of Environment-friendly Usage of Spent Wash and its Nutritional Potential for Sugarcane Production

Excessive and inappropriate use of fertilizers is a key factor of low sugarcane yield and degradation of soil. A two-year (2013–14 and 2014–15) field study was conducted to assess the impact of combined application of organic and inorganic fertilizers on sugarcane at research farm of Shakarganj Sugar Research Institute, Jhang, Pakistan. Experiment was conducted under randomized complete block design with three replications. Treatments were used as control (no exogenous application), spent wash (160 t ha^?1), (nitrogen, phosphorus and potassium) NPK (168:112:112 kg ha^?1), spent wash (120 t ha^?1) + NPK (42:28:28 kg ha^?1), spent wash (80 t ha^?1) + NPK (84:56:56 kg ha^?1), spent wash (40 t ha^?1) + NPK (126:84:84 kg ha^?1), and spent wash (160 t ha^?1) + NPK (42:28:28 kg ha^?1). Application of spent wash @ 80 t ha^?1 + NPK @ 84:56:56 kg ha^?1 resulted maximum crop growth rate (11.35 g m^?2 d^?1), leaf area index (7.78), and net assimilation rate (2.53 g m^?2 d^?1). Maximum number of millable canes (14), weight per stripped cane (0.90 kg), stripped cane yield (117.60 t ha^?1) and unstripped cane yield (141.25 t ha^?1) were observed with spent wash @ 80 t ha^?1 + NPK @ 84:56:56 kg ha^?1, followed by sole fertilizer application @ 168:112:112 kg NPK ha^?1 and spent wash @160 t ha^?1 + NPK @ 42:28:28 kg ha^?1. Similar trend was observed regarding quality parameters. The maximum benefit–cost ratio (1.80) was achieved with integrated application of spent wash @ 80 t ha^?1 + NPK @ 84:56:56 kg ha^?1.     

Inoculation of rapeseed under different rates of inorganic nitrogen and sulfur fertilizer: impact on water relations,cell membrane stability,chlorophyll content and yield

It is important to develop integrated fertilization strategies for various crops that enhance the competitive ability of the crop, maximize crop production and reduce the risk of nonpoint source pollution from fertilizers. In order to study the effects of mineral nitrogen fertilization and biofertilizer inoculation on yield and some physiological traits of rapeseed (Brassica napus L.) under different levels of sulfur fertilizer, field experiments in factorial scheme based on randomized complete block design were conducted with three replications in 2012 and 2013. Experimental factors were: (1) four levels of chemical nitrogen fertilizer (0, 100, 150 and 200 kg N ha^?1), (2) two levels of biofertilizer (with and without inoculation) consisting Azotobacter sp. and Azospirillum sp. and (3) two levels of sulfur application (0 and 50 kg S ha^?1). Rapeseed yield, oil content of grains and studied physiological traits had a strong association with the N fertilization, biofertilizer inoculation and sulfur (S) application. Higher rates of N fertilization, biofertilizer inoculation and S application increased the grain yield of rapeseed. In the case of physiological traits, the highest value of relative water content (RWC) was recorded in 100 kg N ha^?1 that was statistically in par with 150 kg N ha^?1 application, while usage of 150 kg N ha^?1 showed the maximum cell membrane stability (CMS). Inoculation with biofertilizer and S fertilization resulted in higher RWC and CMS in rapeseed plants. The chlorophyll content showed its maximum values in the highest level of N fertilization, biofertilizer inoculation and S application. The usage of 200 kg N ha^?1 significantly decreased the oil content of rapeseed grains, but the highest grain oil content was obtained from the application of 150 kg N ha^?1, Azotobacter sp. and Azospirillum sp. inoculation and S fertilization. It seems that moderate N rate (about 150 kg N ha^?1) and S application (about 50 kg S ha^?1) can prove to be beneficial in improving growth, development and total yield of inoculated rapeseed plants.     

Relationships between microbial biomass nitrogen,nitrate leaching and nitrogen uptake by corn in a compost and chemical fertilizer-amended regosol

Abstract

To determine the relationships between microbial biomass nitrogen (N), nitrate–nitrogen leaching (NO₃-N leaching) and N uptake by plants, a field experiment and a soil column experiment were conducted. In the field experiment, microbial biomass N, 0.5 mol L^?1 K₂SO₄ extractable N (extractable N), NO₃-N leaching and N uptake by corn were monitored in sawdust compost (SDC: 20 Mg ha^?1 containing 158 kg N ha^?1 of total N [approximately 50% is easily decomposable organic N]), chemical fertilizer (CF) and no fertilizer (NF) treatments from May 2000 to September 2002. In the soil column experiment, microbial biomass N, extractable N and NO₃-N leaching were monitored in soil treated with SDC (20 Mg ha^?1) + rice straw (RS) at five different application rates (0, 2.5, 5, 7.5 and 10 Mg ha^?1 containing 0, 15, 29, 44 and 59 kg N ha^?1) and in soil treated with CF in 2001. Nitrogen was applied as (NH₄)₂SO₄ at rates of 220 kg N ha^?1 for SDC and SDC + RS treatments and at a rate of 300 kg N ha^?1 for the CF treatment in both experiments. In the field experiment, microbial biomass N in the SDC treatment increased to 147 kg N ha^?1 at 7 days after treatment (DAT) and was maintained at 60–70 kg N ha^?1 after 30 days. Conversely, microbial biomass N in the CF treatment did not increase significantly. Extractable N in the surface soil increased immediately after treatment, but was found at lower levels in the SDC treatment compared to the CF treatment until 7 DAT. A small amount of NO₃-N leaching was observed until 21 DAT and increased markedly from 27 to 42 DAT in the SDC and CF treatments. Cumulative NO₃-N leaching in the CF treatment was 146 kg N ha^?1, which was equal to half of the applied N, but only 53 kg N ha^?1 in the SDC treatment. In contrast, there was no significant difference between N uptake by corn in the SDC and CF treatments. In the soil column experiment, microbial biomass N in the SDC + RS treatment at 7 DAT increased with increased RS application. Conversely, extractable N at 7 DAT and cumulative NO₃-N leaching until 42 DAT decreased with increased RS application. In both experiments, microbial biomass N was negatively correlated with extractable N at 7 DAT and cumulative NO₃-N leaching until 42 DAT, and extractable N was positively correlated with cumulative NO₃-N leaching. We concluded that microbial biomass N formation in the surface soil decreased extractable N and, consequently, contributed to decreasing NO₃-N leaching without impacting negatively on N uptake by plants.     

Impact of mineral and organic fertilization on yield,C content in the soil,as well as on C,N and energy balances in a long-term field experiment

Data from a 49-year-long organic–mineral fertilization field experiment with a potato–maize–maize–wheat–wheat crop rotation were used to analyse the impact of different fertilizer variations on yield ability, soil organic carbon content (SOC), N and C balances, as well as on some characteristic energy balance parameters. Among the treatments, the fertilization variant with 87 kg ha^?1 year^?1 N proved to be economically optimal (94% of the maximum). Approximately 40 years after initiation of the experiment, supposed steady-state SOC content has been reached, with a value of 0.81% in the upper soil layer of the unfertilized control plot. Farmyard manure (FYM) treatments resulted in 10% higher SOC content compared with equivalent NPK fertilizer doses. The best C balances were obtained with exclusive mineral fertilization variants (?3.8 and ?3.7 t ha^?1 year^?1, respectively). N uptake in the unfertilized control plot suggested an airborne N input of 48 kg ha^?1 year^?1. The optimum fertilizer variant (70 t ha^?1 FYM-equivalent NPK) proved favourable with a view to energy. The energy gain by exclusive FYM treatments was lower than with sole NPK fertilization. Best energy intensity values were obtained with lower mineral fertilization and FYM variants. The order of energy conversion according to the different crops was maize, wheat and potato.     

Effect of 13 Years Long Minimum Tillage Cum Conjunctive Nutrient Management Practices on Soil Fertility and Nitrogen Chemical Fractions under Sorghum (Sorghum bicolour (L.) Moench)–Mungbean (Vigna radiata (L.) Wilczek) System in Semi-Arid Tropical Alfisol (SAT) in Southern India

A long-term experiment was conducted at the Central Research Institute for Dryland Agriculture for 13 years to evaluate the effect of low tillage cum cheaper conjunctive nutrient management practices in terms of productivity, soil fertility, and nitrogen chemical pools of soil under sorghum–mung bean system in Alfisol soils. The results of the study clearly revealed that sorghum and mung bean grain yield as influenced by low tillage and conjunctive nutrient management practices varied from 764 to 1792 and 603 to 1008 kg ha^?1 with an average yield of 1458 and 805 kg ha^?1 over a period of 13 years, respectively. Of the tillage practices, conventional tillage (CT) maintained 11.0% higher yields (1534 kg ha^?1) over the minimum tillage (MT) (1382 kg ha^?1) practice. Among the conjunctive nutrient management treatments, the application of 2 t Gliricidia loppings + 20 kg nitrogen (N) through urea to sorghum crop recorded significantly highest grain yield of 1712 kg ha^?1 followed by application of 4 t compost + 20 kg N through urea (1650 kg ha^?1) as well as 40 kg N through urea alone (1594 kg ha^?1). Similar to sorghum, in case of mung bean also, CT exhibited a significant influence on mung bean grain yields (888 kg ha^?1) which was 6.7% higher compared to MT (832 kg ha^?1). Among all the conjunctive nutrient management treatments, 2 t compost + 10 kg N through urea and 2 t compost + 1 t Gliricidia loppings performed significantly well and recorded similar mung bean grain yields of 960 kg ha^?1 followed by 1 t Gliricidia loppings + 10 kg N through urea (930 kg ha^?1). The soil nitrogen chemical fractions (SNCFs) were also found to be significantly influenced by tillage and conjunctive nutrient management treatments. Further, a significant correlation of SNCF with total soil nitrogen was observed. In the correlation study, it was also observed that N fraction dynamically played an important role in enhancing the availability pool of N in soil and significantly influenced the yield of sorghum grain and mung bean.