Application of QUEFTS Model for Site-Specific Nutrient Management of NPK in Sweet Potato (Ipomoea batatas L. Lam)

Sweet potato productivity in India is either stagnated or lowering down over the past many years. The main reasons for low yield are conventional blanket recommendation of fertilizers, lower nutrient-use efficiency and imbalance in the use of fertilizers. Recommendation of major nutrients, nitrogen, phosphorus, and potassium (NPK), based on quantitative approaches will augment sweet potato production per unit area by increasing the nutrient-use efficiency. The present study calibrated the Quantitative Evaluation of Fertility of Tropical Soils (QUEFTS) model for the estimation of NPK requirements and fertilizers recommendations for different target yields of sweet potato. The QUEFTS basically works on the principle of NPK nutrient interactions and climate-adjusted yield potential of a region. Published data sets from several field experiments related to NPK carried out till date were collected to reflect the environment variability. The results of the present study showed that to produce one ton tuber, 16:6:18 kg N, P, and K, respectively, would be needed with the internal efficiencies of 61:167:57 kg tubers kg^?1 NPK removed. The maximum accumulation and dilution (kg tuber kg^?1 nutrient removed) of N (40, 80), P (96, 272), and K (30, 85) were also derived as standard parameters in QUEFTS for optimum fertilizer recommendation in tropical and subtropical regions of India. The observed yields of sweet potato with different amounts of nutrients were in agreement with the values predicted by the model. Therefore, it is utmost important to have the results of the study validated in major growing environments of India for fertilizer recommendation in sweet potato.     

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.     

Site-specific nutrient requirements of NPK for potato (Solanum tuberosum L.) in Western Indo-gangetic plains of India based on QUEFTS

Abstract

Potato productivity in India is static due to unbalanced use of nutrients and intensive cropping system. Nutrient use efficiency and yield can be increased by application of nutrients based on quantitative approaches. We calibrated the quantitative evaluation of fertility of tropical soils (QUEFTS) model for the estimation of NPK requirements for different targeted yields of potato. Published data sets were used to calibrate the model. The results of the study showed that to produce one ton of potato tubers, 18, 4, and 24?kg N, P, and K, respectively, would be needed with internal efficiencies of 55, 285, and 42?kg tuber dry yield/kg N, P, and K removed. The observed yields of potato with different amount of nutrients were in agreement with the values predicted by the model. Therefore, the QUEFTS model based NPK fertilizer recommendations can be adopted for site-specific nutrient management of potato.     

Maize Yield Response to Zinc Sources and Effectiveness of Diagnostic Indicators

Maize yield is often limited by zinc (Zn) deficiency. The objectives of this study were to (i) evaluate maize yield response to Zn applied at four different rates, (ii) evaluate the yield response and agronomic efficiency of maize to the application of a complex fertilizer, MicroEssentials SZ (12N–40P–0K–10S–1Zn), compared to different rates of monoammonium phosphate (MAP) + ammonium sulfate (AS) + zinc sulfate (ZnSO4), and (iii) evaluate the association between tissue Zn concentration and soil-test Zn with the maize response to Zn fertilizer. Eleven experiments were carried out during the 2010, 2011, and 2012 growing seasons throughout eight states in the USA. Treatments consisted of four Zn rates of a physical blend of MAP + AS + ZnSO₄ (0, 2.24, 4.48, 6.72, and 11.2 kg/ha Zn) and MicroEssentials SZ at a Zn rate of 2.24 kg/ha Zn. Nitrogen, phosphorus (P), and sulfur (S) rates were balanced across treatments (40 kg/ha P, 22 kg/ha S) and fertilizers were broadcast and incorporated immediately prior to planting. Treatment and location main effects were significant (P < 0.001) on corn yields, whereas the interaction treatment × location was not (P = 0.33). Maize responded positively to Zn fertilization; average yields across locations increased from 10,540 kg ha^?1 without Zn to 11,530 kg ha^?1 with 11.21 kg Zn ha^?1 applied as a physical blend. The yield response and Zn agronomic efficiency of maize with the application of the complex fertilizer at a rate of 2.24 kg Zn ha^?1 averaged 1004 kg ha^?1 and 448 kg maize kg Zn^?1, respectively, significantly higher (P < 0.1) than the yield response and Zn agronomic efficiency with the application of a physical blend with the same Zn rate, which averaged 293 kg ha^?1 and 131 kg maize kg Zn^?1, respectively. The Zn concentration in plant tissue of unfertilized plots varied greatly and was not related to the maize response to Zn fertilizer (r = 0.01; P = 0.98). With respect to soil Zn, a negative but nonsignificant relationship was found between maize response to Zn fertilizer and soil-test Zn (r = ?0.51; P = 0.16).     

Productivity,Quality and Soil Health as Influenced by Organic,Inorganic and Biofertilizer on Field Pea in Eastern Himalaya

A field experiment was conducted during two consecutive years of 2010–2011 and 2011–2012 to study the effect of biofertilizers in conjunction with organic and inorganic sources of nutrient management on productivity, quality and soil health on field pea at ICAR RC for NEH Region, Nagaland Centre Jharnapani, Nagaland, India. The experiment was laid out in split plot design with five nutrient sources in main plots and four treatment of biofertilizers with zinc in sub plots. Results indicated that the application of 100% recommended dose of fertilizer (RDF) through inorganic + 50% recommended dose of nitrogen (RDN) through vermicompost significantly improved root nitrogen (N) content, cation exchange capacity (CEC) of roots, NA activates, seed yield (1153 and 1262 kg ha^?1), straw yield (2182 and 2332 kg ha^?1) in the year of 2010–2011 and 2011–2012, respectively. Nutrients (N, P, K, S and Zn) uptake by seed and straw, protein content, protein harvest, soil organic carbon (SOC), available N, P, K, S, Zn and economics significantly higher with 100% RDF through inorganic + 50% RDN through vermicompost during both the years. Seed inoculation with biofertilizers along with 5 kg Zn ha^?1 markedly enhanced the root N content, CEC of roots, nitrogenase activities (NA), seed yield (1080 and 1193 kg ha^?1), straw yield (1978 and 2128 kg ha^?1), nutrients [N, phosphorus (P), potassium (K), sulfur (S) and zinc (Zn)] uptake, soil organic carbon (SOC) (%), and available N, P, K, S, and Zn of pea in both the years, respectively. These sources also give more income and benefit cost ratio per rupees invested.     

Quantitative determination of NPK uptake requirements of taro (Colocasia esculenta (L.) Schott)

Taro yield in many parts of the world is stagnant mainly due to conventional blanket recommendation of fertilizers, lower nutrient use efficiency and imbalance in the use of nutrients. The Quantitative Evaluation of Fertility of Tropical Soils (QUEFTS) model was used for determining the region specific balanced NPK uptake requirements and recommendations for a target yield of taro. The constants for minimum and maximum accumulation (kg cormel kg^?1 nutrient) of N (33 and 177), P (212 and 606) and K (25 and 127) were derived as standard model parameters. The results showed that taro requires N, P and K accumulation of 12.97, 2.75 and 17.47?kg t^?1 of cormel yield, suggesting an average NPK ratio in the plant dry matter of about 4.7:1:6.4. The NPK fertilizer requirements for different potential yield situations were also calculated. The results need to be validated in major taro growing regions.     

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 the Response of Cassava to Fertilizers: A Site-Specific Nutrient Management Approach for Greater Tuberous Root Yield

Conventional fertilizer-management strategy results in decreased fertilizer-use efficiency and unbalanced nitrogen (N)–phosphorus (P)–potassium (K) applications. The quantitative evaluation of fertility of tropical soils (QUEFTS) model was used for determining region-specific balanced NPK uptake requirements and recommendations for a target yield of cassava. Minimum and maximum internal efficiencies of N, P, and K were estimated as 35 and 80 for N, 250 and 750 for P, and 32 and 102 for K (kg tuberous root per kg nutrient removed). Linear increases in tuberous root yield with N, P, and K uptakes of 17.6, 2.2, and 15.6 kg N, P, and K per 1000 kg tuberous root yield were observed. Relationships between soil supply and soil chemical properties and between fertilizer nutrient recovery efficiencies with their rates of application were developed for major cassava-production regions. Good agreement between measured and predicted yields was observed while calibrating the model, which shows that the model can be used for making site-specific NPK recommendations for cassava in major cassava production regions of India.     

采用QUEFTS建立向日葵推荐施肥模型养分特征参数

  【目的】  汇总我国向日葵主产区的产量和施肥效应数据,构建基于产量反应与农学效率的推荐施肥模型,为向日葵科学施肥提供依据。  【方法】  收集整理2002年以来在向日葵主产区进行的向日葵肥料田间试验和公开发表的文献等共483个,计算产量反应、农学效率、肥料利用效率等特征参数。采用QUEFTS法预估向日葵地上部氮 (N)、磷 (P)、钾 (K)养分吸收。  【结果】  我国主要产区向日葵籽粒产量平均为3334.9 kg/hm2,秸秆产量平均为7222.7 kg/hm2,收获指数为0.32 kg/kg。籽粒中N、P₂O₅和K₂O养分含量平均分别为25.0、4.7和8.5 g/kg,秸秆中平均分别为8.4、1.2和32.8 g/kg,地上部N、P₂O₅和K₂O养分吸收量平均分别为145.7、55.1和318.5 kg/hm2。N、P₂O₅和K₂O养分收获指数平均分别为0.59、0.66和0.11 kg/kg,施用N、P和K的内在效率 (IE) 分别为23.8、63.8和11.3 kg/kg,籽粒需要的养分吸收量 (RIE) 分别为43.2、16.4和94.9 kg/t。应用QUEFTS模型估算,目标产量为最高产量的60%～70%时,生产1 t籽粒地上部需要吸收N 40.8、P₂O₅ 15.8和K₂O 78.1 kg,N∶P₂O₅∶K₂O养分需求比例为2.58∶1.00∶4.93。N、P和K肥的产量反应 (YR) 分别为621.9、467.0和361.3 kg/hm2。不施用N、P和K的相对产量 (RY) 分别为0.82 (n = 1071)、0.87 (n = 914) 和0.90 (n = 1108)。相对产量与施肥产量反应之间呈显著的线性负相关,N、P和K相对产量与施肥产量反应关系的决定系数 (R2) 分别达到了0.712*(n = 1071)、0.693* (n = 914) 和0.763* (n = 1108)。向日葵N、P和K肥的增产量和农学效率二者间存在着显著的指数曲线关系,决定系数 (R2) 分别达到了0.634* (n = 1061)、0.697* (n = 905) 和0.702* (n = 1092)。其关系式分别为AE_N = 0.0152YR_N0.8796;AE_P = 0.0269YR_P0.8797;AE_K = 0.0229YR_K0.9009。  【结论】  通过向日葵养分增产量(产量反应)与相对产量,及产量反应与农学效率的相关关系可计算出养分需要量。氮肥推荐可依据氮肥的增产量和农学效率来确定,磷、钾肥推荐除考虑其增产量及吸收量外,还需考虑一定目标产量下地上部的养分移走量、上季残效和通过秸秆还田的归还量。     

Integrated Effects of Mulching Treatment and Nitrogen Fertilization on Cotton Performance under Dryland Agriculture

ABSTRACT

Crop production in arid regions is characterized with high temperature, drought and salinity which decrease water and nutrient use efficiency. This study was conducted to investigate the effect of wheat residue mulch in relation to N fertilizer application rates for cotton productivity under dryland condition of Uzbekistan. Main plots were control of no mulch addition and a 5 t ha^?1 mulch treatment. These plots were split into 5 N rate plots of 0, 70, 140, 210 or 280 kg of N ha^?1. The results showed that mulching pattern decreased soil temperature by 0.7–1.5°C as compared to conventional treatment (CT), regardless of N fertilization rates. The soil water storage increased by 41.8, 17.3, 48.0 mm in the flowering, boll formation and ripening stages of cotton, respectively under mulching treatment. Soil available N concentration and nutrients uptake by plants consistently increased with the increase of N fertilization rates with positive correlations. At flowering period, the plant height, chlorophyll content, stem diameter, and a number of fruit branches in plants were higher by 32.3%, 46.8%, 26.7% and 55.3%, respectively at 210 kg N ha^?1 under mulching treatment as compared to the non-fertilized control. The highest cotton yield was obtained at 210 kg N ha^?1 application under mulching treatment. The correlation difference between mulch and N application rates was higher (R² = 0.97) than the difference in CTs and N application rates (R² = 0.89). This study showed that mulching had a greater impact to preserve nutrients and water resources in the soil, thereby improved cotton growth and yield.     

Evaluation of White yam (Dioscorea rotundata) genotypes for arbuscular mycorrhizal colonization,leaf nutrient concentrations and tuber yield under NPK fertilizer application

Yield decline in yam may not only be due to soil nutrient depletion but also to the activity of soil microflora. Arbuscular mycorrhizal (AM) symbiosis helps in plant nutrition but may be affected by the application of fertilizer. The effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizer rates on the AM colonization, leaf nutrient concentrations, and tuber yields of eleven genotypes of Dioscorea rotundata were investigated at Ibadan, Nigeria. The soil was ferric luvisol. Eleven genotypes were selected from the previously conducted screening of 75 genotypes of D. rotundata for fertilizer response. Four application rates: 0, 200, 400, and 600 kg ha^?1 of NPK 15-15-15 were applied in a split plot design with four replications. Fertilizer rate was the main plot and variety was the sub plot. Percentage AM colonization was significantly reduced at 600 kg ha^?1 but not at lower rates when compared to zero rate and it was negatively correlated with leaf N, P, and zinc (Zn) concentrations. Leaf N concentrations were significantly increased at 200 kg ha^?1 in five genotypes and at 600 kg ha^?1 in two genotypes compared to zero application. Leaf P and K concentrations were decreased with the application of fertilizer in most of the genotypes. The NPK fertilizer of 15-15-15 at the rate of 200–400 kg ha^?1 gave yield response in eight genotypes of D. rotundata, with minimal or no effect on their AM colonization when compared to zero application. Long term study on the effect of fertilizer application on AM symbiosis in yam is recommended.     

Effect of Low‐Rate Commercial Humic Acid on Phosphorus Availability,Micronutrient Uptake,and Spring Wheat Yield

Abstract

A greenhouse study was conducted to determine the effects of low‐rate commercial humic acid (HA) on phosphorus (P), iron (Fe), and zinc (Zn) availability and spring wheat yields, in both a calcareous soil and a noncalcareous soil. In Phase I, soluble P concentrations were monitored at 1.9, 3.8, and 5.7 cm from a monoammonium phosphate (MAP) fertilizer band that had either been coated with one of two HA products at the equivalent of 1.7 kg HA ha^?1, a label rate, or left uncoated. Sampling occurred periodically up to 48 d after fertilizer application. In Phase II, uptake of P, Fe, and Zn and grain yield were measured in soils that had been fertilized with 7.5 or 25 kg P ha^?1, either coated with HA or left uncoated. In Phase I, only three significant differences (P=0.05) out of 66 comparisons were found in soluble P concentrations between HA and control treatments at time points ranging from 4 to 48 d after fertilization. In addition, no significant differences were found in nutrient uptake, shoot biomass, or grain yield between HA and control treatments. These greenhouse results suggest that low commercial HA rates (～1.7 kg HA ha^?1) may be insufficient to enhance spring wheat growth.     

Nutrient constraint of rainfed rice production in foot slope soil of Guinea Forest in Côte d’Ivoire

Soil nutrient deficiencies can affect rice yield and grain mineral content wherever they occur, but an understanding of their effect on upland rice production in humid forest zone of West Africa is still limited. Therefore, a nutrient omission trial was conducted on foot slope soil in 2003, 2004 and 2005 in Côte d’Ivoire using rice variety WAB 56–104. The effect on rice grain yield (GY) and nutrient content of complete fertilizer (Fc with nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and zinc (Zn)) was compared with Fc from which a specific nutrient was excluded (Fc – N, Fc – P, Fc – K, Fc – Ca, Fc – Mg and Fc – Zn). Before the trial, soil K (0.10 cmol kg^?1) and Mg (0.20 cmol kg^?1) contents were suitable, but available P-Bray I (4.2 mg kg^?1) was found to be deficient. In course of the study, K, Mg and P deficiencies were observed. An antagonistic effect was observed between rice GY and grain concentrations in P, Mg and Ca for treatments Fc – Mg, Fc – P and Fc – K, respectively. Therefore, the use of P, K and Mg fertilizers is recommended for successive cropping seasons in order to rich stable and high rice yield while decreasing of grain concentrations in P, Mg and Ca can be observed.     

Integrated Fertilizer Management: Influence on Soil Nitrogen,Available Phosphorus,Potassium, Nutrient Uptake and Maize Yield

A field experiment was conducted on an Alfisol (kandic paleustalf) in Abeokuta, Southwestern Nigeria, for two seasons to assess the influence of inorganic and organic fertilizers on nitrogen (N), phosphorus (P), potassium (K), nutrient uptake and maize yield. The treatments consisted of three rates of organic fertilizer 0, 5 and 10 t ha^?1 in the form of poultry manure and NPK fertilizer (20:10:10) applied at 0 and 120 kg ha^?1. Maize (Zea mays) was used as the test crop. The results showed that the combined application of 10 t ha^?1 poultry manure and 120 kg ha^?1 NPK fertilizer enhanced the uptake of N, P and K better than other treatment combinations. Application of 10 t ha^?1 poultry manure alone gave the highest grain yield, which was 67.02% higher than the control in the first season. Complementary application of 5 t ha^?1 poultry manure with 120 kg ha^?1 NPK 20–10-10 was recommended for grain yield.     

优化施肥对小麦品质和产量的效应研究

采用正交旋转组合设计,针对N、P、K、Zn 4种肥料对小麦产量和品质的效应进行探讨,结果表明:N、P对产量都达显著正效应,N对湿面筋含量达极显著正效应,P与湿面筋含量呈显著负效应,K、Zn对产量和品质效应微弱。4种肥料对产量的影响顺序为:N>P>Zn>K,对湿面筋含量的影响顺序为:N>P>K>Zn。小麦产量和品质都较理想的施肥区间为N 252.8～294.2 kg/hm2,P 111.0～139.1kg/hm2, K145.8～153.0kg/hm2, Zn 9.8～12.1kg/hm2, 合理的配比为N:P2O5:K2O:ZnSO4=1:0.46:0.55:0.04     

Nutritional Evaluation of Nitrogen and Potassium Fertilization of Carob Tree under Dry‐Farming Conditions

Abstract

The aim of this work was to assess how potassium (K) and nitrogen (N) fertilization might affect the variation of leaf and fruit nutrient concentrations in carob tree (Ceratonia siliqua L.) under low precipitation. A field study was conducted in 1997, 1998, and 1999 in a calcareous soil. Four fertilization treatments were tested: no fertilizer (C), 0.8 kg N tree^?1 (N treatment), 0.83 kg K tree^?1 (K treatment), and 0.80 kg N tree^?1 plus 0.83 kg K tree^?1 (NK treatment). During the hydrological cycle 1998/1999, only 250 mm of rain were recorded. Because of this, from 1998 to 1999 a decrease in the concentrations of mobile nutrients N, phosphorus (P), and K and an increase in calcium (Ca), iron (Fe), and manganese (Mn) were observed in leaves. The application of N led to higher leaf N concentration compared with other treatments. This response allowed the establishment of a linear model that relates soil plant analysis development (SPAD) readings with leaf N concentrations (r²=0.55; P<0.05). Compared with leaves, fruits showed similar amounts of N and P; less Ca, Mg, Fe, and Mn; and high concentrations of K. Fertilization did not change considerably the mineral composition of fruits, and because of large variation among trees, yield was similar for all treatments.     

Grain yield,nitrogen use efficiency and tillage intensity in wheat as affected by precision nutrient management

ABSTRACT

The present studies were conducted to evaluate the effect of different nutrient management practices under two tillage options in wheat. The experiments were laid out in split-plot design with a combination of two varieties (WH 1105 and HD 2967) and two tillage options (Conventional and No tillage) in the main plot and six precision nutrient management practices [absolute control, site-specific nutrient management with Nutrient Expert for wheat (SSNM-NE)(170 kg nitrogen (N)/ha), SSNM NE+GreenSeeker (GS)(153/158 N kg/ha), N₁₂₀ (120 kg N/ha) before irrigation, N₁₂₀ after irrigation and N Rich (180 kg N/ha)] in subplot replicated thrice. The grain yield and quality characters in no tillage (NT) and conventional tillage (CT) were similar but agronomic efficiency was higher in NT. Both the varieties (WH 1105 and HD 2967) gave similar grain yield and quality. Wheat variety WH 1105 recorded significantly higher sodium dodecyl sulfate sedimentation (SDS) and gluten index. The treatment SSNM NE+GS had resulted in 107.1% higher grain yield than no nitrogen control but similar to enriched N plot (180 kg N/ha). The grain protein, SDS and gluten index in need-based nutrient management (SSNM+GS) treatment were found to be similar as recorded in SSNM-NE (170 kgN/ha) and N enriched plot (180 kg N ha^?1). The agronomic efficiency and recovery efficiency in SSNM+GS were also better than SSNM NE.     

Nutrient Mineralization from Nitrogen- and Phosphorus-Enriched Poultry Manure Compost in an Ultisol

The combination of inorganic fertilizers and compost is a technique aimed at improving crop growth and maintaining soil health. Understanding the rate of nutrient release from enriched compost is important for effective nutrient management. A laboratory incubation study was conducted for 112 days to study the nutrient mineralization pattern of poultry manure compost enriched with inorganic nitrogen (N) and phosphorus (P) fertilizer nutrients in an Ultisol. Compost applied at the rate of either 5 or 10 g kg^?1 was blended with N (50 kg N ha^?1) and P (30 kg P ha^?1). Carbon dioxide evolution and N and P mineralization were measured fortnightly. The bacterial and fungal populations were determined at the mid and end of the experiment. The combination of compost and inorganic N and P increased carbon (C) and P mineralization by 4?8% and 56?289%, respectively, over the application of either compost or inorganic N and P. However, P addition influenced the amount of C mineralized. Inorganic N and P, on the other hand, were better at increasing N mineralization than compost blended with inorganic N and P over a short time. The addition of compost stimulated bacterial and actinomycete populations, while fungal populations were unaffected. Actinomycetes and bacteria had similar and higher relationship trend with C (R² = 0.24) and P (R² = 0.47) mineralization and were key determinants in nutrient mineralization from compost in this Ultisol. Integrating compost with inorganic fertilizers improves nutrient availability through the growth and activities of beneficial microorganisms.     

轮作体系下冬油菜养分利用效率的区域研究

Fertilization is essential for oilseed rape because it is sensitivity to nutrient deficiency, especially for winter oilseed rape(Brassica napus L.). To investigate regional nutrient efficiency and nutrient uptake-yield relationship of winter oilseed rape in an intensive cropping system, this study used data from 619 site-year on-farm experiments carried out in the winter oilseed rape planting area of the Yangtze River Basin, China from 2005 to 2010, with large yield in the range of 179–4 470 kg ha~(-1). Currently recommended application rates of N, P and K fertilizers increased rapeseed yield at different levels of soil indigenous nutrient supply(INS) in this region. Boundary values of plant nutrient uptake were established to analyze the nutrient uptake-yield relationship of winter oilseed rape(internal nutrient efficiency), i.e., 128 kg N ha~(-1), 24 kg P ha~(-1), and 122 kg K ha~(-1). The internal nutrient efficiency declined by 48.2%–64.1% when nutrient uptake exceeded the boundary value, resulting in excessive nutrient uptake(i.e., low yield response with high nutrient uptake), especially for K. In the intensive cropping system, agronomic efficiencies of N, P, and K were 5.9, 3.4, and3.6 kg kg~(-1), and recovery efficiencies of N, P, and K were 35.6%, 24.1%, and 36.8%, respectively. These findings showed that the fertilization rate should be optimized by considering INS, nutrient status, and nutrient efficiency of winter oilseed rape. In this study,considering the lower yield improvement to high K uptake levels and low K fertilizer efficiency, application rate of K fertilizer should be reduced since soil K deficiency has already been mitigated.     

Nutrient constraint and yield potential of rice on upland soil in the south of the Dahoumey gap of West Africa

With the objective of improving rice productivity and generating additional knowledge on rice production in Africa, field experiments were conducted for two consecutive seasons of 2005 and 2006 in Southern Benin. Terre de barre soils at the WARDA experimental station and Niaouli, and the plinthic Ferralsols of Cana were investigated. A complete fertilizer (Fc) composed of N, P, K, Ca, Mg and Zn was used to assess NERICA.4 (upland rice) root development and grain yield (GY). Similar observations were made in treatments with a specific nutrient excluded from Fc (Fc–N, Fc–P, Fc–K, Fc–Ca, Fc–Mg and Fc–Zn). A grain yield of up to 1.4 t ha^?1 (Fc–N) and higher root densities for Fc and Fc–Mg at 20–60 cm were attained. Maximum reductions in yield and rooting depth were observed for Fc–P (27%, 27%), Fc–K (30%, 14%) and Fc–Zn (32%, 2%). Drought occurrence, a high C/N ratio and soil acidity influence the effects of nutrients on rice. Removal of N from basal fertilizer was recommended to reduce the effect of mid-season drought. It is suggested that the critical level of K in the soils of West Africa be adjusted to 0.40 cmol kg^?1 for upland rice.