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The overestimation of potassium (K) levels in ammonium acetate extractant has led to a significant concern in calcareous soil (CS). Therefore, a pot experiment was conducted to investigate the response of K application on grain yield and to determine the most suitable extractant along with their critical limits. The study utilized soil collected from both calcareous and non-calcareous soils, which were subjected to ten levels of K in a completely randomized design with three replications. The findings revealed that K application had a positive effect on yield and yield parameters in calcareous soils, up to 13.5%, with a response up to 7.5 mg kg−1. The study also demonstrated that grain and straw K concentrations were 2.5% and 8.9% higher, respectively, in calcareous soils when compared to non-calcareous soils (NCS). The study also tested the effectiveness of different extractants in extracting K from both soils. The available K extracted using various extractants varied, with the highest correlation coefficient (r = 0.87***) found in the barium chloride (BaCl2) extractant. The critical limit of soil-K by Cate-Nelson method was found to be 964.3 kg ha−1 for 0.1 M BaCl2, 0.74% for grain, and 3.55% in straw in CS. In conclusion, K application had a significant effect on yield and yield parameters in calcareous soils, with barium chloride being the most effective extractant for estimating potassium levels. The findings of this study provide valuable insights into the appropriate extractants and critical limits for the accurate evaluation of K levels in calcareous soils. [ABSTRACT FROM AUTHOR]

Manganese (Mn) is an essential micronutrient for plants, which influences multiple physiological systems. Determination of the critical limit (CL) of Mn in the soil is necessary for Mn fertilizer application as this limit delineates the deficiency, optimum, and toxicity ranges of Mn. A pot experiment was performed in the winter season with 20 soils collected from three Agro-Ecological Zones (AEZs) of Bangladesh to determine the CL of Mn for soybean (Glycine max L.). Manganese was applied in soil @ 0, 1, 2, and 4 ppm, and the experiment was laid out in a factorial and completely randomized design with three replications. The CL of Mn was determined by the Cate-Nelson graphical and statistical approach and was found 3.60 and 3.55 µg g−1, respectively. Applying 1 µg g−1 Mn in soil significantly enhanced root and shoot weight, as well as seed yield of soybean compared to no Mn application. In field conditions, a significant positive response of soybean yield was found up to the CL of Mn. The findings of the study could help predict possible Mn deficiency in soil and soybean response to Mn fertilizer, which is important in decision-making for efficient fertilizer management practices to ensure the yield potential of soybeans. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess soil quality and identify main indicators and their critical limits as a function of relative rice yield in northern Iran. In present study, 60 topsoil (0–30 cm) samples were collected and 18 physical, chemical, and biological soil attributes were measured and analyzed. Based on the mean rice yield obtained from sampling sites, paddy fields were divided into fields with low (< 4.5 t ha−1) and high (≥ 4.5 t ha−1) productivity. Using the principal component analysis (PCA), among 18 soil indicators, 4 indicators were selected as the minimum dataset (MDS) including soil organic carbon (OC), urease activity, bulk density (BD), and available Zn (AZn). The upper and lower limits of MDS indicators and soil quality index (SQI) were defined using scatterplot. The results showed that the mean SQI of high productivity fields (0.95) was significantly higher than that in low productivity fields (0.77). The upper and lower limits for soil OC were 3.5 and 1.0 (g 100 g−1), urease activity 84 and 43 (μg NH4 g soil−1 2 h−1), BD 1.84 and 1.60 (g cm−3), and AZn 2.0 and 0.6 (mg kg−1), respectively. The soil quality assessment using SQI accounted for 52% of the rice yield variation. Thus, management practices and mitigation of soil limiting factors should be comprehensively investigated to ensure sustainable rice production in the paddy fields of northern Iran. [ABSTRACT FROM AUTHOR]

Critical limit (CL) determination of zinc (Zn) is much more important to assess the response of crop to its application in soils and for crops actual fertilizer requirement. This experiment was conducted at University of Agricultural Sciences, Bangalore in sandy clay loam texture soils. Based on the results of the pot culture experiment, the critical limits of DTPA, AB-DTPA, Mehlich-3, tomato plant and tomato fruit are 1.12, 1.20, 2.15, 34 and 58 mg kg−1, respectively. Tomato was highly responded to Zn application in soils below the critical limit whereas soils with Zn greater than 1.12 mg kg−1 did not respond much. For the confirmation of pot culture results, two field experiments were carried out during 2017–18 with different Zn treatments one in high and other in low zinc soils. The study concluded that for both low zinc and high zinc soils external application of zinc through Recommended dose of fertilizers (RDF) + ZnSO4 @ 30 kg ha−1 as soil application (SA) + foliar application (FA) @ 0.50% ZnSO4 and RDF + ZnSO4 @ 20 kg ha−1 as SA + FA @ 0.25% ZnSO4 significantly improved yield, nutrient concentration and uptake of nutrients, which helped in getting higher benefit cost (B:C) ratio of 4.74 and 4.96, respectively. This information is helpful in site-specific zinc nutrition in tomato and to enhance the productivity and profitability. [ABSTRACT FROM AUTHOR]

Introduction[1]Ecosystem Services frameworks are emerging as an approach of capturing the wider impacts of policy decisions or evaluating land use change in order to more comprehensively take into account the range of effects on the environment, and on the benefits humans receive from. The Millennium Ecosystem Assessment (MA) (2005) defines ecosystem services as ‘‘the benefits that humans obtain from ecosystems”. Costanza et al. (1997) postulated that ecosystem services comprise of ‘‘flows of materials, energy, and information” from the natural environment to the society. Yield and production for agricultural crops have been improved during the last century, however, these achievements have caused different environmental social and safety problems for human and the environment such as increase in greenhouse gases, eutrophication of rivers, lakes and other water bodies.This study aimed to evaluate environmental consequences of agroecosystems managed conventionally in three Razavi Khorasan, South Khorasan and North Khorasan Provinces. The environmental consequences of intensive agriculture were grouped into damages maid to natural resources such as water, air, soil, biodiversity and human health affected by over-consumption of chemical fertilizer, herbicide and pesticide.Materials and MethodsCultivated area and consumption of chemical inputs in North Khorasan, South Khorasan and Razavi Khorasan provinces during 2004-2009 were determined. Environmental impacts were calculated using six categories i.e. air (emission of greenhouse gases such as N2O, CO2 and CH4 to the atmosphere), water (quality criteria such as NO3- and pesticide concentrations in water), soil (amounts of NO3-, organic carbon, pesticides and herbicides in soil), biodiversity (losses of pastures, jungles and bee hives), human health (residues of Diazinone, Azinophos-Methyl and NO3- in some vegetables) and natural resources (losses of nitrogen fertilizers via leaching and volatilization and pesticides consumption effects) affected by chemical inputs such as fertilizers, herbicides and pesticides.Results and discussionResults indicated that decreasing trends in use of chemical pesticide and herbicide were observed in different agroecosystems of Khorasan. Nitrate of water used in agricultural area was higher than allowable limit of 10 mg per liter. Residues of chemical herbicide including Diazinone and Azinophos- Methyl in irrigated water were 23.18±16.35 and 15.78±0.68 mg.kg-1, respectively. The maximum emission of greenhouse gases including CO2, CH4 and N2O were calculated in Razavi Khorasan. Nitrate concentration in the soil was higher than the critical limit. Organic carbon content in natural habitat and rangeland was higher than that in the cropland. Also, total number of honey hives was increasing but the hives for local bees were almost reaching to zero in the recent years. The maximum range of nitrate for tomato, eggplant, cucumber and spinach were 1.4, 0.75, 17.15 and 7.38% higher than allowable limit, respectively. For sugar beet upper and lower limits of nitrate were lower than the allowable limit. ConclusionSoil is a very slow forming resource, and similarly to other habitats and ecosystems, it is coming under intensifying pressures due to anthropocentric and industrial activities. Soil ecosystem services provide multiple benefits to all organisms.Nitrate concentration for leafy vegetable was higher than for kitchen garden plants. Nitrogen and phosphorus contents for soil in Razavi Khorasan were higher relative to North Khorasan and South Khorasan. Nitrogen enhanced soil carbon accumulation as it stimulates plant growth and its productivity. However, accumulation of soil carbon depends on the delicate balance between increased carbon inputs to soil from litter and enhanced soil respiration rates. Crop residues and manure are returned to the soil in traditional farming systems, improving soil ecosystem services and soil chemical, physical and biological characteristics. On the other hand, application of inorganic and chemical fertilizers to benefit crop yields often decreases the soil services as it has negative influences on soil structure, infiltration and water-holding capacity.

Boron is relatively immobile in plants and its deficiency can cause serious yield reduction in rice by retarding panicle formation. Karaiakal region of Puduchuerry union terittory includes different soils with varying fertility status thus supplying boron at optimum level is a must concern to enhance the rice productivity.A pot experiment was conducted to fix critical limits of boron in soils and rice of this Karaikal region. Forty surface soil samples (0-15 cm) were collected from Inceptisol, Entisol and Vertisol soil orders of different locations in Karaikal region. The experiment was conducted with three levels of boron viz., 0, 1 and 2 ppm applied through borax in a factorial completely randomized design with three replications. The available B content of soil was estimated with five extractants. The critical limits of hot water, hot 0.01 M CaCl2, 0.05 M HCl, 1.0 M NH4OAc, 0.01M CaCl2+ 0.05 M Mannitol extractable B were found to be 0.50, 0.58, 0.46, 0.45 and 0.39 ppm in Inceptisol, 0.48, 0.59, 0.44, 0.39 and 0.48 ppm in Entisol and 0.45, 0.54, 0.45, 0.44 and 0.41ppm in Vertisol and a critical limit of 31.0, 39.0 and 34.0 ppm B in rice plant for Inceptisol(0.5ppm), Entisol(0.48 ppm) and Vertisol(0.45 ppm) as determined by Cate and Nelson's graphical procedure. Among the extractants the hot water extractant showed the highest significant and positive correlation with Bray's percent yield(0.48,0.47and 0.48), plant B content(0.041*, 0.019* and 0.271*) and B uptake(0.012*, 0.646* and 0.293*), respectively in Inceptisol, Entisol and Vertisol. From this study, the indicating knowledge of critical limit of boron will help to avoid yield loss of rice in the study region. [ABSTRACT FROM AUTHOR]

Background: Since the spread of Severe Acute Respiratory Syndrom Corona Virus 2 (SARS-CoV‑2) in Germany, intensive care beds have been kept free for patients suffering from Corona Virus Disease (COVID-19). Also, after the number of infections had declined, intensive care beds were kept free prophylactically; however, the percentage of beds reserved for COVID-19 differ in the individual federal states in Germany. The aim of this article is to define a necessary clearance quota of intensive beds for COVID-19 patients in Germany. An escalation and de-escalation scheme was created for rising and falling numbers of infected patients.Methods: Data from the COVID-19 resource board of the state of Baden-Württemberg, the daily situation report of the Robert Koch Institute (RKI), the register of COVID-19 intensive care beds of the German Interdisciplinary Association for Intensive Care and Emergency Medicine (DIVI) as well as the daily report of COVID-19 Baden-Württemberg from April to November 2020 were used for the calculation.Results: At the end of November 2020 approximately 13.5% of intensive care beds in Germany were used by COVID-19 patients. Of all persons tested positive for SARS-CoV‑2, 1.5% were admitted to an intensive care unit. The hospitalization rate was 6% and the mean age of infected persons was 43 years. Based on these numbers hospitals are recommended to keep 10% of intensive care beds available for COVID-19 patients in the case of less than 35 new infections/100,000 in the catchment area, 20% should be kept free in case of an advanced warning level of 35 new infections/100,000 inhabitants and 30% for a critical limit of 50 new infections/100,000 inhabitants. Further internal hospital triggers, such as the occupancy of the intensive care beds with COVID-19 patients, should be considered.Conclusion: If the number of infections is low a general nationwide retention rate of more than 10% of intensive care beds for COVID-19 patients is not justified. Locally increasing numbers of infections require a local dynamic approach. If the number of infections increases, the free holding capacity should be increased according to a step by step concept in close coordination with the local health authorities and other internal hospital triggers. In order not to overwhelm hospital capacities in the event of local outbreaks, a corresponding relocation concept should be considered at an early stage. [ABSTRACT FROM AUTHOR]

From a homeland security point of view, it is important to detect the transportation of radioactive materials or potential radioactive contamination. The most commonly used devices are radiation portal monitors with plastic scintillation detectors. A signal from such detectors is processed by an amplitude analyser which can separate pulses into several mutually independent energy windows (representing energy intervals of gamma radiation). Therefore, the most appropriate method of evaluation is by the use of algorithms for multidimensional processing. This article describes a novel generalised approach designed with respect to the properties of radiation portal monitors. It includes a description of formulas and a whole algorithm as well as the procedure for determining the appropriate critical and detection limits. The predicted probability distribution for the proposed method of calculation was verified by simulations and experimental measurements. The algorithm was also compared with a commonly used gross counting algorithm.

Predictions of ectotherms' responses to global warming depend on the relationship between environmental temperature and organismal performance. To date, most predictions of thermal responses are generated from experimentally derived measures of thermal tolerances of adults or estimates of thermal niches derived from geographic distributions of adults. It is unknown how measures derived from these different approaches compare, or, as thermal performance of ectotherms varies through ontogeny, how they compare across life stages.To understand the efficacy of the temperature–performance relationship of early developmental stages as predictors of geographic range, we empirically documented the upper and lower thermal tolerance limits of embryos of eight species of ectotherms with complex life cycles.We compared the embryonic thermal tolerances of each species to that of the adults (documented in a previous study), as well as to an estimate of the thermal niche derived from adult distributions.Our results show that in all eight species the upper thermal limit estimated from embryos is significantly lower than the upper thermal limit estimated from adults. The lower thermal limit for embryos and for adult performance are similar, but the lower thermal limit for adult survival is significantly lower.Warming tolerances, calculated as the difference between upper tolerance limit and the average ambient temperature during the warmest month, for each species are also smaller for embryos (~1°C) than for adults (~5°C).These results show that thermal tolerances of early developmental stages, which are often easier to obtain for large sample sizes over an array of temperatures than are tolerances of adults, are a powerful, and potentially more accurate tool for predicting future responses to climate change. A free Plain Language Summary can be found within the Supporting Information of this article [ABSTRACT FROM AUTHOR]

(0, 5, 10, 15, 20 and 25 kg ha-1) on the soil available major nutrients, field experiments were conducted in 14 farmer's holdings at Pudukkottai district with hybrid maize (NK 6240) as a test crop. Dry matter production (DMP) of the whole plant (above ground) at harvest stage of maize was significantly influenced by the application of 100% NPK + 10 kg Mg ha-1 and recorded the highest mean as 25620 kg ha-1 at harvest stage. A noticeable increase in grain and stover yield of maize crop was manifested by applying 100% NPK + 10 kg Mg ha-1 which recorded the highest mean yield as 11.6 t ha-1 and 14.0 t ha-1, respectively. It reported a 14.31 and 22.25 per cent increase in grain and stover yields, respectively, over control. [ABSTRACT FROM AUTHOR]

This study was carried out to determine the impact of the HACCP control system on the safety of the final products of collagen hydrolysate production. The object of the study was equine connective tissue. Using the FMEA model, established by a three-factor assessment of the risk priority number (RPN), critical control points (CCP) in the processes of hydrolysis, inactivation of the enzyme preparation, drying and storage were identified. For two CCP, measures for continuous monitoring were identified, and critical limits were developed. For CCT 1, the calculation of optimal fermentation processes using a mathematical model for the hydrolysis of raw materials is given. The optimal values of the Neutrase enzyme, providing a maximum content of water-soluble proteins of 55.0 mg/cm3, were determined: T=37 °C, dosage 5 Pa/g, t=210 min. For CCP 2, to avoid protein denaturation during hydrolysis, a critical limit was developed by determining the heat inactivation point and optimum temperature. Experimental analyses show that the inactivation point of the Neutrase enzyme, estimated by the rate of FTN accumulation, which has 20 % at 60 °C, is reached at the 11th minute. As a result of the study, the effect of enzyme preparations on the safety of collagen hydrolysate was also determined. The result confirms that the Neutrase enzyme preparation had a positive effect on all safety indicators compared to the Trypsin enzyme. The optimal parameters for reducing microbiological indicators, pesticides, antibiotic and toxic metals are: T=40 °C, duration 210 min, dosage of the Neutrase enzyme 5 units/Pa. The results can be used in collagen hydrolysate production to better ensure the quality and safety of the final product [ABSTRACT FROM AUTHOR]

A survey was undertaken during 2018 to assess silicon (Si) status of soils and to determine its critical limits in soils and plants. A total of 100 surface soil samples (0–15 cm) were collected from 7 major rice growing soil series of Periyar Vaigai Command (PVC) area of Tamil Nadu, India based on their percent coverage. Plant available Si in soils was extracted by 1 M sodium acetate (pH 4.0) and varied from 4 to 250 mg kg−1. Based on the results of pot culture experiment, the critical limit of Si for grain and straw of rice (Oryza sataiva L.) variety ADT-45) determined was 0.49 and 2.53 percent respectively. Similarly the critical limit of soil Si established was 122 mg kg−1. Based on this critical limit, soils were classified into low (< 122 mg kg−1), medium (122 to 181 mg kg−1) and high (> 181 mg kg−1). Rice plants were highly responded to Si application in soils below the critical limit of 122 mg kg−1 whereas soils with Si above 181 mg kg−1 did not respond. Among the levels of Si, 225 mg kg−1 of Si was found to be the optimal dose in Si deficient soils to get higher rice grain yield. [ABSTRACT FROM AUTHOR]

Critical limit (CL) determination of zinc (Zn) is very important for predicting response of maize crop to its application in soils and for the crop's actual fertilizer requirement. This study was conducted at Bangladesh Agricultural Research Institute, Gazipur, to determine the CL of Zn for maize grown in 20 soils collected from the five Agro–Ecological Zones during January to March, and April to June of 2017. The available Zn content of soils and maize biomass were estimated utilizing the extraction method with 0.005 M diethylene triamine pentaacetic acid (DTPA). During January to March and April to June 2017, the amount of DTPA extractable Zn in different soils ranged from 0.60–3.25 mg kg−1 and 0.50–1.68 mg kg−1, respectively. During both periods of crop growth (January to March and April to June, 2017), the soil available zinc was negatively significantly correlated with soil pH, available P, exchangeable Ca, exchangeable Mg and positively significantly correlated with relative dry matter (DM) yield. Soil Zn also positively significantly correlated with maize tissue Zn content (r = 0.521*). However, the CL of Zn were estimated to be 0.84 mg kg−1 in soils and 26.1 mg kg−1 in maize tissue for maize cropping as determined by Cate and Nelson's (1965) graphical procedure. Maize crop may respond to Zn application in soils containing Zn at/below the above level. This data may be used for predicting plant response to Zn fertilizer and development of crop Zn nutrition guide for maximum production. [ABSTRACT FROM AUTHOR]

Sulphur is essential for growth and development of groundnut (Arachis hypogaea L.). Deficiency of S is widespread in soils of India, and is becoming a major concern for the quality and yield of groundnut crop. Therefore, a study was conducted to investigate the response of groundnut to S application in alluvial Inceptisols of West Bengal with four levels of S, i.e. 0, 15, 30 and 45 kg/ha. The critical limits of Sulphur in soil and plant for deï¬ciency, adequacy and toxicity were determined from Bray percent yield (BPY). The amount of CaCl2 extractable S in soils varied from11.90–29.17 mg/kg while the critical level for deficiency of S in groundnut was graphically 18.6 mg/kg and statistically 19.58 mg/kg in soils. Application of S increased groundnut yield signiï¬cantly, concentration of S in plant and its uptake by groundnut parts. The critical limit was determined to be 3.0 g/kg for groundnut plants and 4.42 g/ kg for groundnut nuts at harvest.

Northeastern China has long-term densely tilled soils that supply approximately 20% of the annual total national grains. There are very few reports on the agricultural soil quality subjecting to the predatory tillage. Here, the soil quality index (SQI) of a brunisolic soil was calculated using the minimum data set (MDS) and integrated quality index (IQI). The topsoil layer was divided into plow layer (11.9 ± 1.9 cm) and plow pan (11.4 ± 2.6 cm) in fields of high yields (HYB), medium yields (MYB), and low yields (LYB). Our results showed that the MDS of the topsoil layer only contained chemical indicators. The bulk density (BD), as one of the most important soil quality indicators, was found of no significant differences in the topsoil layers. In different layers (i.e., the topsoil layer, plow layer, and plow pan), the value of SQI presented a consistent tendency of HYB > MYB > LYB (p < 0.05). The correlation between SQI and yield was higher in the plow layer (0.60) and plow pan (0.63) than the topsoil layer (0.47). This further verified the reasonability of using soil stratification for SQI calculation. Our findings indicate the potential of using soil quality assessments to examine soil productivity (e.g., fertilizer deficiency) in crop lands with soil stratification. [ABSTRACT FROM AUTHOR]

Nickel (Ni) is an essential element for plants. Abundant information exists on Ni toxicity in soil-plant system but not much is available on its critical level of deficiency (CLD) in soils and plants. Five chemical extractants were evaluated to find a suitable extractant for Ni in Inceptisol. Twenty-one soils having low to high levels of Ni were used to grow barley (Hordeum vulgare L). The amount of Ni extracted was correlated with Ni concentration and uptake by barley. The diethylene triamine penta acetic acid-calcium chloride (0.005 M DTPA-CaC12) was identified as the most promising soil extractant for Ni. The CLD of Ni for 0.005 M DTPA-CaC12 in soil was 0.22 mg kg−1 whereas in barley plant it was 2.14 mg kg−1. Application of 7.5 mg kg−1 Ni in soil caused a significant increase in Ni concentration in the shoot of barley in all the soils irrespective of the initial Ni status. [ABSTRACT FROM AUTHOR]

This paper introduces a windowing algorithm for radiation portal monitors based on a transformation of random variables to calculate the ratio between the radiation intensity in two energy windows. Procedures to evaluate critical limits and establish detection limits are described. Simulations and experimental data illustrate a good agreement between derived and observed ratio distributions. The algorithm was compared with commonly-used algorithms. The results illustrate proper evaluation of critical and detection limits even in the case of shadow shielding by vehicles entering a radiation portal monitor. [ABSTRACT FROM AUTHOR]

Pot culture experiment was conducted to evaluate the suitability of extractants and to determine the critical limit of boron (B) in soil and mustard plant in Inceptisols of Varanasi. Twenty-one bulk soil collected from different locations were used for growing mustard. Five extractants, namely hot water, hot 0.01molar (M) calcium chloride (CaCl2), 0.01M CaCl2 + 0.05 M mannitol, 1.0 M ammonium acetate (NH4OAC) and 0.05 M hydrochloric acid (HCl), were assessed by correlating the amount of extractable B in untreated and B fertilizer-treated soil with Bray’s per cent yield, plant tissue B concentration and B uptake by mustard. Similarly, correlation coefficients of the B extracted by different extractants and soil properties were calculated. The suitability of B extracted by different extractants was in the order of hot 0.01M CaCl2(HCC-B) > hot water (HW-B) > 1.0 M NH4OAC (AA-B) > 0.05M HCl (HA-B) > 0.01M CaCl2 + 0.05M mannitol (CCM-B). The critical limits of extractable B in soil as determined by the graphical procedure were 0.54, 0.60, 0.36, 0.45 and 0.45 mg kg−1and the statistical procedures were 0.54, 0.60, 0.38, 0.46 and 0.48 mg kg−1with HW-B, HCC-B, CCM-B, AA-B and HA-B, respectively. Soil containing available B below the critical limit responded to B fertilization. [ABSTRACT FROM AUTHOR]

Rice-rice is one of the major cropping systems in Indo-Gangetic Plains (IGP) of South Asia. Assessment of soil quality and identification of key indicators with their critical limits are very much important for maintaining normal functioning of the soil and productivity of crops, particularly of wet land rice. The present investigation was undertaken to identify sensitive soil quality indicators and to develop soil quality indices and establishment of their critical limits in Inceptisols, Entisols and Alfisols collected from farmers' fields with long-term rice-rice cropping system in sub-tropical India. The soil samples were analysed for 37 physical, chemical and biological properties. Principal component analysis (PCA) was performed to create minimum data set (MDS) of physical, chemical and biological indicators which were encompassed to develop unified soil quality index (SQI) under different soil orders. The SQI thus developed was highest in Inceptisols (0.66 to 0.89) followed by Entisols (0.23 to 0.76) and Alfisols (0.37 to 0.60). The upper and lower critical limits for key indicators as well as SQI were determined using scattered plot technique involving relative yields of rice (RY) and different soil quality indicators as well as SQI. The critical limit equivalent to 80% and 40% of relative yield were treated as upper and lower critical limits of selected key indicators and SQI. The adequacy classes for each of selected key indicator as a function of relative yield of rice were established based on the following criteria: < 40% low, 40–80% moderate and > 80% adequate. The upper and lower critical limits of the indicators selected under rice-rice cropping systems in Inceptisols were available Zn (1.7 and 1.2 mg kg − 1 ), bulk density (1.2 and 1.6 Mg m − 3 ), β-glucosidase activity (68 and 18 μg p-nitrophenol g − 1 soil h − 1 ) and urease activity (64 and 24 μg NH 4 g − 1 soil 2 h − 1 ), in Entisols were dehydrogenase activity (93 and 12 μg TPF g − 1 soil 24 h − 1 ), aggregate stability (66 and 11%), total organic C (11.6 and 10.7 g kg − 1 ) and pHw (5.7 and 5.3) and in Alfisols were oxidisable organic C (7.8 and 5.0 g kg − 1 ), β-glucosidase activity (51 and 15 μg p-nitrophenol g − 1 soil h − 1 ), aggregate stability (52 and 19%) and mineralizable C (273 and 173 μg C g − 1 soil), respectively. The upper and lower critical limits established for key soil quality indicators as well as soil quality indices for Inceptisols (0.85 and 0.56), Entisols (0.23 and 0.65) and Alfisols (0.37 and 0.56) could periodically be judged for maintaining/enhancing soil quality and yield sustainability through the employment of optimum management practices in rice-rice cropping systems of subtropical India. [ABSTRACT FROM AUTHOR]

Response of tomato to a blanket application of 50kg Mg ha-1 was studied at 20 locations on soil available Mg ranged from 40.6ppm to 172.4ppm. This range can be classified exchangeable Mg low to high status. These plots were selected from intensive tomato growing areas of southern Karnataka. The yield responses obtained from these plots were used to calculate the soil and plant Mg critical levels. Using scattered plot technique soil Mg limit of 74ppm is arrived as critical soil Mg for tomato crop. Similarly a plant critical limit of 0.39% was established to separate deficient plants from those having sufficient Magnesium.