A validated mechanistic model of carrot (Daucus carota L.) growth

A mechanistic model of carrot vegetative and root development was constructed. This model determined canopy photosynthesis over a day, assimilates were then partitioned into either roots or leaves via temperature dependent partitioning coefficients. Assimilates were lost via terms describing growth and maintenance respiration. The model was calibrated on data from four different carrot cultivars, originating from the UK (Autumn King), Syria (Carrot_S), Poland (Dolanka) and Russia (Hibinskaja), grown in controlled environment glasshouse compartments at one of six temperatures (9–30 °C) repeated over three sowing dates. Calibration of the model showed that it could account for between 83 and 95% of the variance in carrot plant and root dry weights. The model was then validated using independent data from the same cultivars of carrots grown in the field at Reading. In this instance, the model accounted for 75 and 79% of the variance in plant and root weight, respectively. Two other independent data sets were used to validate the model, including carrot of a different cultivar (Panther) grown in phytotrons at temperatures between 9 and 21 °C, at two different locations and over a three sowing dates. In this instance, the model accounted for between 63 and 69% of the variance in root weight. The model also predicted that if ambient carbon dioxide levels increased from 348 to 551 μmol mol⁻¹, root dry weight would increase by 12%, which is within the margin of error of the experimental value of 16% reported in the literature. The model can therefore be used to study the potential impacts of global climate change on carrot production, as well as to rapidly predict whether germplasm is suited to any particular environment.     

Prediction of Major Agricultural Fruits Production in Pakistan by Using an Econometric Analysis and Machine Learning Technique

ABSTRACT

The aim of this study was to use an econometric analysis to investigate the relationship between agricultural gross domestic product (AGDP) and variables such as apple, citrus, pears, grape and banana in Pakistan; data were explored from 1980 to 2015; we used time series data collected from secondary sources, including the Pakistan Bureau of Statistics, Statistical Year Books and the Economic Survey of Pakistan. Data were analyzed by using the Ordinary Least Square (OLS) method and Augmented Dickey Fuller (ADF) test, and results were interpreted by using the Johansen co-integration test. The machine learning technique was used to examine and predict the future agricultural productivity in Pakistan. We found that output of banana, citrus and pears had a positive and significant influence on AGDP, whereas apples and grapes had a negative but insignificant influence on AGDP.     

Effects of ammonium and inorganic carbon enrichment on growth and yield of a hydroponic tomato crop

Effects of varying the proportions of NO₃^— and NH₄⁺ in the growth medium on seedling growth and tomato fruit yield (Lycopersicon esculentum L. cv. Trust F1) were investigated in greenhouse hydroponic experiments. The presence of NH₄⁺ as the sole N source (11 mM) was toxic: it curtailed growth and decreased chlorophyll content of the leaves. However, at low concentration (10 % of total N), the presence of NH₄⁺, with or without added dissolved inorganic carbon (DIC), increased vegetative growth and fruit yield by ˜ 15 %, and enhanced taste/flavor of the fruits. In DIC‐enriched treatment, pH was maintained at 5.8 by addition of KHCO₃ or as CaCO₃. The presence of NH₄⁺, at 10 % of total N, inhibited NO₃^— uptake rates by ˜ 27 %. The rates of uptake of NO₃^— and NH₄⁺ were comparable (13.3 and 14.2 mmol plant^—1 d^—1, respectively, in the presence of DIC, and 14.7 and 14.0 mmol plant^—1 d^—1, respectively, in the absence of DIC), despite such a large difference in their concentrations in the nutrient feed solution. A higher proportion of NH₄⁺ (up to 50 % of total N) had no further significant effect upon early vegetative growth, but in a long‐term experiment resulted in a high incidence of blossom end‐rot (BER) disease, thereby severely curtailing fruit yield. The presence of even 1.1 mM NH₄⁺ reduced Ca²⁺ and Mg²⁺ accumulation in the leaves as well as in fruits.     

Influence of organic and inorganic passivators on Cd and Pb stabilization and microbial biomass in a contaminated paddy soil

Purpose

Soil contamination with heavy metals, such as Cd and Pb, has caused severe health and environmental risks all over the world. Possible eco-friendly solutions for Cd and Pb immobilization were required to reduce its mobility through various cost-effective amendments.

Materials and methods

A laboratory incubation study was conducted to assess the efficiency of biochar (BC), zeolite (ZE), and rock phosphate (RP) as passivators for the stabilization of Cd and Pb in paddy soil as well as soil microbial biomass. Various extraction techniques were carried out: a sequential extraction procedure, the European Community Bureau of Reference (BCR), toxicity characteristic leaching procedure (TCLP) test, and single extraction with CaCl₂. The impact of passivators on soil pH, dissolved organic carbon (DOC), and microbial biomass (carbon, nitrogen, and phosphorus) was examined in the metal contaminated soil.

Results and discussion

The results showed that the exchangeable portion of Cd in soil was significantly reduced by 34.8, 21.6, and 18.8% with ZE, RP, and BC at a 3% application rate, respectively. A similar tendency of reduction in Pb soluble portion was observed by ZE (9.6%), RP (20%), and BC (21.4%) at a 3% application rate. Moreover, the TCLP leachate of Cd and Pb was apparently reduced by 17 and 30.3% with BC at a 3% application dose, respectively, when compared to the control. Soil pH, nutrients, and microbial biomass C, N, and P were significantly increased with the addition of BC, RP, and ZE passivators.

Conclusions

The results showed that the incorporation of BC, ZE, and RP significantly reduced the Cd and Pb mobility in paddy soil as well as enhanced soil nutrients and microbial biomass. Overall, among all the amendments, rice straw derived-BC performed better for Cd and Pb immobilization in paddy soil.

     

Soybean (Glycine max) Extracts Impact on Plant and Soil Biology

The aim of the present investigation was to determine the phytotoxic effect of aqueous extract from fresh and oven-dried leaves and roots of soybean plants on maize growth and on rhizosphere soil. The extract prepared from fresh leaves of drought-stressed soybean plants significantly increased the accumulation of proline, soluble sugar, and endogenous abscisic acid (ABA) content of maize-treated plants. Increase in antioxidant activity like superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT), and endogenous ABA was recorded in treated plants. The soybean leaf extracts prepared from drought-stressed plants significantly decreased the soil pH and electrical conductivity (EC) of maize cultivated soil. The soybean drought-stressed leaf extracts prepared plants were found more effective in modulating the physiology of maize, indicating the higher allelopathic potential of soybean.     

Carbon mineralization in response to nitrogen and litter addition in surface and subsoils in an agroecosystem

More than 50% of global soil organic carbon stocks are stored below 20 cm of soil depth capable of massively altering global C cycle and climate. However, subsoil C dynamics are largely overlooked implicitly assuming that surface and subsoil C dynamics are similar. Here, we compared the soil C dynamics in surface and subsurface soil layers in response to nitrogen and maize leaf litter additions. Soils, sampled from 0 to 5, 15 to 35, 35 to 55 and 55 to 75 cm depths, were incubated at 25°C after adding litter, nitrogen (NH₄NO₃) or litter plus nitrogen. Soil respiration (C mineralization) was measured throughout the incubation period. Litter addition significantly increased C mineralization in all the soil layers. However, the soil CO₂ release relative to control was more than twofold higher in 15–35 and 35–55 cm soil layers than the surface layer. Nitrogen additions significantly decreased C mineralization in 0–15 cm soil, increased in 35–55 cm and had minimal effects in the 15–35 and 55–75 cm layers. Different soil C dynamics in surface and subsurface soil layers found in our study contradict the general assumption that soil C dynamics may be treated similarly along different soil depths.     

A comparison of the effect of organic acids and dicalcium phosphate supplementation on phosphorus bioavailability,growth performance and digestive enzyme activities of Labeo rohita fingerlings

The effect of organic acids (OA) and dicalcium phosphate (P_i) supplementation in the feed of Labeo rohita fingerlings was studied by formulating seven practical diets, designed as D1 with no feed additives {dicalcium phosphorus (P_i) and organic acid (OA) blend} while, D2, D3, D4 and D5 were supplemented with P_i at the graded levels of 5, 10, 15 and 20 g/kg, respectively, whereas D6 and D7 contained blend of OA at 15 and 30 g/kg, respectively. The diet supplemented with OA blend exhibited increase (p < .05) in growth of L. rohita fingerlings compared with the diet supplemented with P_i. The OA supplementation at both levels showed significant improvement in nutrients digestibility and minerals absorption in fingerlings. Moreover, in case of muscle proximate composition, crude fat (CF) and crude protein (CP) were increased (p < .05) with the inclusion of OA blend in the diet while crude ash (CA) was improved by P_i supplementation. Additionally, digestive enzyme activities were not affected (p ? .05) by OA blend supplementation while increased activities were observed in the fingerlings fed with P_i diet. Consequently, supplementation of OA blend in the diet improved the growth performance and nutrient status while P_i enhanced digestive enzyme activities of L. rohita fingerlings.     

Chemometric Methods to Predict of Pb in Urban Soil from Port Pirie,South Australia,using Spectrally Active of Soil Carbon

A total of 73 soil samples were initially analyzed for lead (Pb) concentration as an indicator of the environment impact of smelter activity in the Port Pirie, South Australia. Chemometric techniques were used to assess the ability of near-infrared (NIR) reflectance spectroscopy to predict soil Pb using spectrally active soil characteristics such as soil carbon (C). The result indicated a strong linear relationship between log-transformed data of soil Pb and spectral reflectance in the range between 500 and 612 nm with R² = 0.54 and a low root-mean-square error (RMSE_v = 0.38) for the validation mode with an acceptable ratio of performance to deviation and ratio of error range (1.6 and 7.7, respectively). This study suggested that NIR spectroscopy based on auxiliary spectrally active components is a rapid and noninvasive assessment technique and has the ability to determine Pb contamination in urban soil to be useful in environmental health risk assessment.     

Effect of humic acid on growth and crop nutrient status of wheat on two different soils

The effect of plant-derived humic acid (PDHA) and coal-derived humic acid (CDHA) on wheat growth was tested on two alkaline calcareous soils in pots. Humic acid derived from plant and coal materials was applied at the rate 0 (control), 50 and 100 kg/ha to wheat in pots carrying two soils viz. clayey loam soil and sandy loam soil separately. Data was collected on plant growth parameters such as spike weight, grain and straw weight, and plant nutrients (macronutrients and micronutrients). Results showed that spike weight increased by 19%, 15%, and 26%, and 11% with application of PDHA at the rate of 50 and 100 mg/kg in clayey loam and sandy loam soil, respectively. Grain yield show an increase of 21% and 11% over control with application of PDHA and CDHA at the rate of 50 mg/kg on both soils, respectively, and 10% and 22% with application of PDHA and CDHA at the rate of 100 mg/kg on both soils.     

Evaluation of sunflower (Helianthus annuus L.) single cross hybrids under heat stress condition

Sunflower is an important oilseed crop, which shows susceptibility to heat stress. In this study, 63 single cross hybrids were evaluated under heat stress condition for 2 years and compared with the two commercial hybrids. Genotype and genotype × environment (GGE) was used to differentiate single cross hybrids on the basis of multiple traits. GGE biplot showed that several single cross hybrids had higher seed yield potential than standard check. Moreover, seed yield per plant (SYP) was related to pollen viability percentage, showing that achene yield was the product of high gametophytic fertility under heat stress. Hybrids having high seed yield potential under heat stress had lower cell membrane injury. GGE biplot for SYP and its components showed that single cross hybrids were characterized into two major groups. Group I was further characterized into two sub group. Group Ia included hybrids with high 100-SW, while group Ib had the hybrids with high number of seeds per head and head diameter. Group II had the hybrids with high kernel weight and kernel to seed ratio. The hybrids could be recommended according to their potential utilization in the seed industry.