Irrigation,a productive tool for food security – a review

Water scarcity in agriculture is becoming a major problem due to increasing demand from nonagricultural uses and intensive crop management on existing croplands to meet the needs of an expanding global population. Efficient use of the available irrigation water is therefore of important concern. Even though intensive research in the areas of crop physiology, irrigation engineering, agronomy and agricultural economics has developed several ways to improve the efficiency of irrigation water, a multidisciplinary approach is often regarded as the best future path to achieve further enhancements in meeting the forthcoming challenge of producing more and safety foods. Failure of irrigation production has profound effects on the welfare of all those employed in it and also their customers. Indeed, the scale of the industry is such that world food prices will be influenced by the overall performance of the irrigation farmers, but low food prices are essential to the welfare of the poorest people. The contribution of irrigation and water management to increased food production must come through both expansion of irrigation and improved management of existing water supplies. This review presents the past, current and future panorama of irrigation as a viable tool in ensuring food security on the globe. Considering past trends, this review empathizes that future irrigation technologies should be focused on providing the leadership and capacity to capture, develop and promote new irrigation practices and management systems to optimize production.     

Humic matter: basis for life—a plea for humics care

Purpose

Humic matter (HM) is the leftover from life and at the same time the source for new life. The resulting complex system with many interactions has become a crucial part for the anthropocene and by this for the survival of mankind. Based on the results of the application of advanced analytical tools, the structures, reactions and interactions of HM are discussed.

Materials and methods

HM was investigated from different water samples (ground water, bog lake, waste water effluent). Fulvic acids (FA) and humic acids (HA) were isolated from a bog lake and from waste water effluent according to the XAD-method described by the International Humic Substances Society. Parameters like dissolved organic carbon (DOC), spectral absorption coefficient at λ?=?254 nm (SAK), AOX (on activated carbon absorbable organically bound halogen) and THM (trihalomethanes) were determined according to ISO standard methods. For additional characterization, size exclusion chromatography coupled with online DOC detection and solid-state NMR were applied. The degradation of HM was studied by heterogeneous photocatalysis with titanium dioxide. Membrane separation, done as ultra- and nanofiltration, was used to characterize different size fractions of HM.

Results and discussion

The water solubility and hence the omnipresence of HM in aquatic systems opens the door for obtaining well-defined samples for experiments with meaningful results. Information on transport properties and reactivity, derived from the molecular size of HM, was obtained by using membrane filtration at different pore sizes. Photocatalytic degradation of HM was investigated by irradiation of suspensions with TiO₂ as catalyst. Small organic acids (e.g. formic acid) were formed before total mineralisation occurred.

Conclusions

It can be concluded that the properties of HM are well derivable from their molecular data. The resulting character of HM with respect of the human environment seems to be obviously ambivalent and asks for a sound understanding and proper management to support life in a sustainable way.

     

Maturity Tests for Composts — Verification Of a Test Scheme for Assessing Maturity

Increased recycling of organic wastes has raised concern about the quality of compost end products. In addition to the limit values for heavy metals and impurities including weeds and pathogens, the quality criteria for compost products should also include criteria for maturity. There is a tremendous number of maturity assays, developed earlier by several authors, and recommended to be used to evaluate maturity of composts. Because no such single test alone reliably demonstrates the complex properties occurring during maturization of compost, we developed a fast and easy-to-use two-phase test scheme for the assessment of maturity. In the first phase the degradation phase e.g. stability of compost samples is evaluated by using a carbon dioxide evolution test and/or determination of the NO₃-N/NH₄-N ratio by simple test strips. In the second phase, the toxicity of the compost is evaluated by a plant growth test, germination tests and/or the Flash bioluminescence test. Eleven plants composting sewage sludge, source-separated biowaste, manure or a combination of these raw materials were sampled after 1-3 weeks of composting and when the compost was considered “ready for use”. Chemical and physical analyses were considered useful as additional information when evaluating maturity especially when the results were not conclusively clear. This fast and easy-to-use test scheme was designed especially for the composting plant operators and official laboratories responsible for evaluating compost quality.     

Is there a best shape for nature reserves?

It has been hypothesized that nature reserves should be as circular as possible to maximize the total number of species conserved. Using multiple regression, we examined the relationship between species richness on oceanic islands and island shape for 33 data sets. After accounting for the effect of island area, island shape does not explain a significant amount of the residual variation in species number in more data sets than expected due to chance alone. We conclude that if the mechanisms controlling species richness on oceanic islands and isolated patches of terrestrial habitat are the same, then shape is not of major concern in the design of nature reserves.     

Towards a ‘red list’ for crop plant species

An attempt is made toward the application of IUCN criteria and Red List Categories to agricultural and horticultural plants (excluding ornamentals). The main sources for this study were Mansfeld’s Encyclopedia (2001) and the IUCN Red List of threatened plants (2001). About 200 threatened cultivated plants are considered and presented in the respective lists, among them completely extinct crop plants such as Anacyclus officinarum and Bromus mango. The information available about neglected and underutilized crop plants still lags behind that about wild plants, especially at the species level, and more studies are required. On the other hand studies of major crops at the infraspecific level, are very advanced and can serve as models for investigating the wild ones.     

Fluorescence microscopy for visualization of soil microorganisms—a review

Direct microscopic observation of microorganisms is an important tool in many microbial studies. Such observations have been reported for Protozoa, fungi, inoculated bacteria, and rhizosphere microorganisms but few studies have focused on indigenous bacteria and their spatial relationship within various microhabitats. Principles and applications of epifluorescence microscopy and confocal laser scanning microscopy for visualization of soil microorganisms in situ are reviewed. Both cationic and anionic dyes (also commonly referred to as fluorochromes if they are fluorescent) have been used based on their ability to bind to specific cellular components of microbial cells. Common fluorochromes used for imaging of microbial cells include acridine orange, ethidium bromide, fluorescein isothiocyanate, 5-(4,6-dichlorotriazinyl) aminofluorescein, 4,6-diamidino-2-phenylindole, europium chelate, magnesium salt of 8-anilino-1-naphthalene sulfonic acid, and calcofluor white M2R. Combining fluorescence staining techniques with soil thin section technology allows one to obtain images of microorganisms in situ. Soil texture and the procedures used for resin embedding are important factors affecting the quality of stained soil thin sections. Indeed, general limitations of applying fluorescence microscopy to soil ecological studies are the non-specific binding of dyes to the soil matrix and the autofluorescence of some soil components. The development of fluorescent in situ hybridization and confocal laser scanning microscopy techniques provides new potential for microbial distribution studies.     

Microsatellite markers – a new tool for distinguishing diploid wheat species

Triticum baeoticum and T. urartu are very similar morphologically. By using microsatellite markers it was possible to distinguish between these two species. Microsatellite markers are, therefore, a powerful new tool to support the determination of critical races in diploid wild wheat species. They also allow the discussion of evolutionary pathways within Triticum.     

Selenium in agriculture: a nutrient or contaminant for crops?

Selenium (Se) is an essential nutrient for animals, humans, and microorganisms, but its role in the plants needs further exploration. It is considered beneficial at low levels, but is toxic at higher levels, and there is a fine boundary between these concentrations. Generally, Se levels less than 1 mg kg^?1 have been found to be beneficial for the plants while higher levels cause toxicity in most of the agricultural crops. At low concentrations, Se can act as a plant growth regulator, antioxidant, anti-senescent, abiotic stress modulator, and defensive molecule against pathogens in plants. At higher concentrations, plants show various toxic symptoms, which include stunting of growth, chlorosis, withering, and drying of leaves, decreased protein synthesis premature and even death of the plant. The roles of selenium as enhancer and inhibitor of plant growth in various agricultural crops are discussed here with recent updates. Biofortification of some crops with Se using agronomic and genetic approaches is being explored to cultivate them in the regions having Se-deficiency in foods. Strategies of phytoremediation of Se in hyperaccumulators and transgenic plants overexpressing enzyme/proteins to increase Se tolerance are also described.     

Iron‐Enriched Azolla as a slow‐release biofertilizer for cucumber plants grown in a hydroponic system

The unique ability of dried plant residues Azolla to adsorb iron (Fe) was employed to formulate and test an organic Fe biofertilizer. A simplified experimental system was established to examine the effectiveness of Fe‐enriched Azolla as a source of Fe for the remedy of Fe‐deficient plants. The optimal Fe‐enrichment level needed to achieve a complete recovery of starved plant by the Fe‐Azolla complex was tested using a bioassay system of hydroponically grown cucumbers. Dried Azolla plants were mixed a with a solution of ferrous sulfate (FeSO₄) at pH 2.0, rinsed, and dried to form organic, compact material containing 4% (w/w) Fe bound to Azolla. The Fe‐Azolla complex was applied to the nutrient solutions of Fe‐deficient cucumber seedlings. Growth rates and development measurements as well as chlorophyll and the Fe‐containing catalase activity tests have been performed. The effect of the slowly released Fe in correcting Fe deficiency were followed for three weeks and compared with the efficiency of additions of several synthetic Fe chelates. Iron‐starved plants exhibited fast regreening of the chlorotic interveinal tissues after the addition of Fe‐Azolla complex to the nutrient solutions. Iron starvation decreased the activity of catalase. Iron‐treated‐starved plants exhibited recovery of catalase activity compared to the low level activity measured untreated Fe‐starved plants. Iron‐enriched Azolla treatment was found equivalent to Fe‐EDTA and Fe‐EDDHA. This study is the first step in our research program aimed to establish the application of Fe‐enriched Azolla as a bioagent for the benefit of Fe‐deficient crops.     

Milk as a food for growth? The insulin-like growth factors link

OBJECTIVE: The mechanisms underlying the association of insulin-like growth factor-I (IGF-I) and leg length (a marker of prepubertal growth) with cancer risk are uncertain. One hypothesis is that diet in early childhood might provide the link. The aim of the present study was to examine the association between early diet - in particular, the intakes of cows' milk and dairy products - and height, leg length and IGF-I levels at age 7-8 years.SUBJECTS: Children participating in the Avon Longitudinal Study of Parents and Children.DESIGN: Diet was assessed using a 3-day unweighed food record. Anthropometry, IGF-I and insulin-like growth factor-binding protein-3 (IGFBP-3) were measured by standard methods.RESULTS: Data on both diet and height were available for 744 children (404 boys) and on diet and IGF for 538 (295 boys). After adjusting for energy, both cows' milk and dairy product intakes were positively associated with IGF-I (P=0.040 and 0.027, respectively) and IGFBP-3 levels (P=0.082 and 0.067, respectively). These associations persisted on adjustment for potential confounders, but were abolished on controlling for protein intake. In energy-adjusted models there was only weak evidence of associations of milk and dairy product intakes with anthropometry. In boys only, dairy product intake was positively associated with leg length (equivalent to a 0.058 (0.002, 0.114) standard deviation score increase in leg length per 100 g increase in daily intake).CONCLUSIONS: These data provide some evidence that variation in childhood milk and dairy product intakes underlies associations of leg length, IGF-I and cancer risk. The association appears to be due to the protein content of milk.     

Are mineral nutrients a critical factor for lime intolerance of lupins?

Poor growth of lupins on calcareous soils may be attributed to a number of soil physical and chemical factors. Nutrient imbalances, such as deficiency of phosphorus (P) and micronutrients or calcium (Ca) excess have been reported to be responsible for the calcifuge behavior of the plants. In the present study we investigated the importance of nutrient imbalances for the growth reduction of lupins on a lime‐containing soil. Three lupin species (Lupinus luteus, Lupinus angustifolius, and Lupinus albus) were compared with lime‐tolerant Pisum sativum. Plants were cultivated in a sandy soil containing 0.2% or 10% magnesium (Mg) limestone and were fertilized with a complete nutrient solution except for iron (Fe). In each lime treatment, three of six pots per species were supplied with iron as FeEDDHA. Strong liming greatly decreased shoot growth, rate of leaf appearance, and shoot dry matter accumulation in all Lupinus species, but only marginally in P. sativum. All Lupinus species displayed chlorosis on the strongly limed soil, whereas on the slightly limed soil, only L. luteus did so. Shoot concentrations of P, potassium (K), Ca, Mg, manganese (Mn), zinc (Zn), and copper (Cu) were generally in the adequate range. Decreased shoot growth was not associated with increased Ca concentrations. FeEDDHA fertilization alleviated chlorosis in most cases, but was not able to restore shoot growth. Therefore it is concluded, that, at least in the juvenile stage, nutrient imbalances do not play a major role in growth limitation of lupins on calcareous soils.     

Atmospheric sulfur deposition for a red soil broadleaf forest in southern China

A two-year study in a typical red soil region of Southern China was conducted to determine 1) the dry deposition velocity (Vd) for SO2 and particulate SO4^2- above a broadleaf forest, and 2) atmospheric sulfur fluxes so as to estimate the contribution of various fractions in the total. Using a resistance model based on continuous hourly meteorological data, atmospheric dry sulfur deposition in a forest was estimated according to Va and concentrations of both atmospheric SO2 and particulate SO2^4-. Meanwhile, wet S deposition was estimated based on rainfall and sulfate concentrations in the rainwater. Results showed that about 99% of the dry sulfur deposition flux in the forest resulted from SO2 dry deposition.In addition, the observed dry S deposition was greater in 2002 than in 2000 because of a higher average concentration of SO2 in 2002 than in 2000 and not because of the average dry deposition velocity which was lower for SO2 in 2002. Also,dry SO2 deposition was the dominant fraction of deposited atmospheric sulfur in forests, contributing over 69% of the total annual sulfur deposition. Thus, dry SO2 deposition should be considered when estimating sulfur balance in forest ecological systems.     

Is Direct Seeding a Biologically Viable Strategy for Restoring Forest Ecosystems? Evidences from a Meta‐analysis

Ecological restoration has become an important technique for mitigating the human impacts on natural vegetation. Planting seedlings is the most common approach to regain lost forest cover. However, these activities require a large economic investment. Direct seeding is considered a cheaper and easier alternative technique, in which tree seeds are introduced directly on the site rather than transplanting seedlings from nurseries. To evaluate the effectiveness of direct seeding, we conducted a comprehensive search of the literature using ‘restoration’, ‘direct seeding’ and ‘sowing’ as keywords, and we performed a meta‐analysis using 30 papers and 89 species. We used two different measures of restoration success: seed germination probability and success probability (the chance that a seed germinates and survives until the end of the experiment). In general, restoration attempts using direct‐seeding techniques were relatively unsuccessful. On average, seed germination and success probability were 0·239 and 0·114, respectively, and were not affected by climate, species successional group or the application of pre‐germinative treatments. Germination and success probability increased with seed size, and the use of physical protections resulted in a nearly twofold increase in germination probability, but this effect faded by the end of the experiments. Because of the low rate of seedling success, we suggest the use of direct seeding as a complementary technique to reduce restoration costs, particularly for species with large seeds and known high germination rates, but our results do not support direct seeding as a substitute for seedling planting. Copyright © 2015 John Wiley & Sons, Ltd.     

Can we predict the provenance of a soil sample for forensic purposes by reference to a spatial database?

In forensic soil science it is sometimes necessary to address a question of the form: ‘what is the most likely place of origin of this soil material’, where the possible provenances are in a large area. This ‘intelligence’ problem may be distinguished from the ‘evidence’ problem where we need to evaluate the grounds for believing that some soil material is derived from one site rather than another. There is interest in the use of soil databases to solve intelligence problems. This paper proposes a geostatistical method to tackle the intelligence problem. Given data on a sample of unknown provenance, and a database with the same information from known sites, it is possible to define a likelihood function, the argument of which is location in space, which is the likelihood that the sample is from that location. In this paper, we show how an approximation to this likelihood can be computed, using a principal component transformation of the data and disjunctive kriging. The proposed likelihood function is tested using a geochemical database on the soil of the Humber Trent region of north‐east England. This shows that the function is a useful way to make a statistical prediction of the provenance of a soil sample. The region can be stratified according to the value of the likelihood function. A validation data set showed that if we defined a stratum with the top 4.5% of values of the likelihood function, then there was a 50% probablity that it included the true provenance of the sample, and there is a 90% probability of finding the true provenance of the sample in a stratum with the top 30% of values of the likelihood function. Note also that the spatial likelihood function could be integrated with other sources of information on the likely provenance of the sample by means of Baye’s law. We conclude that this approach has value for forensic problems. The main difficulty is how to define the geostatistical support of the forensic specimen, and the reliability of analytical data on relatively small forensic samples, but this is a generic problem for forensic geoscience.     

Detecting Departure From Additivity Along a Fixed-Ratio Mixture Ray With a Piecewise Model for Dose and Interaction Thresholds

For mixtures of many chemicals, a ray design based on a relevant, fixed mixing ratio is useful for detecting departure from additivity. Methods for detecting departure involve modeling the response as a function of total dose along the ray. For mixtures with many components, the interaction may be dose dependent. Therefore, we have developed the use of a three-segment model containing both a dose threshold and an interaction threshold. Prior to the dose threshold, the response is that of background; between the dose threshold and the interaction threshold, an additive relationship exists; the model allows for departure from additivity beyond the interaction threshold. With such a model, we can conduct a hypothesis test of additivity, as well as a test for a region of additivity. The methods are illustrated with cytotoxicity data that arise when Chinese hamster ovary cells are exposed to a mixture of nine haloacetic acids.     

Water‐retention capability as a selection criteria for drought resistance in wheat

Four durum wheat cultlvars (Triticum turgidum spp. durum Desf.) from different countries of origin (Austria, Ethiopia, and Italy) were investigated. Plants were grown in pots under glasshouse conditions. Immediately after the full development of the flag leaves, these leaves were detached for the screening. Distinct differences in water‐retention capabilty among the cultivars was observed. The drought‐resistant (hardy) types, Valgerardo and Boohai, showed better water retention capabilty than the drought‐sensitive ones, such as DZ‐04–688. Poor yielding cultivars under field conditions were also found to be poor in water‐retention capability and vice versa. The applied method is simple and inexpensive. It adds another procedure when screening for drought resistance. However, it needs further confirmation by cultivars covering a broader range of genetic diversity.     

Humic substances: Structure,function and benefits for agroecosystems—a review

The increasing global demand for food production, often causing excessive use of chemical fertilizers, has led to the deterioration of soil health. Immediate action is required to restore soil health in a sustainable manner. This review advocates switching to use of organic matter(manure and compost) that contains vital nutrients for plant growth and helps restore soil health. Humic substances(HSs), derived from degraded plant remains and found ubiquitously in nature,are an important source of o...     

Soil biological changes for a natural forest and two plantations in subtropical China

Conversion of natural forests into pure plantation forests is a common management practice in subtropical China. To evaluate the effects of forest conversion on soil fertility, microbe numbers and enzyme activities in topsoils (0-10 cm) were quantified in two 33-year-old monoculture plantations of Castanopsis kawakamii Hayata (CK) and Cunninghamia lanceolata Lamb. (Chinese fir) (CF), and compared to a neighboring relict natural C. kawakamii forest (NF), in Sanming, Fujian. Five soil samples were collected once each in January, April, July, September and November in 2000 in each forest for laboratory analysis. Over the sampling year, there were significant differences for bacteria, fungi and actinomycetes between forests and between seasons (P < 0.05). The largest bacteria and fungi populations were in NF, while CF contained the greatest number of actinomycetes. There were also significant differences (P < 0.05) with microbial respiration for forests and seasons. Additionally, compared with NF, urease and acid phosphatase were significantly lower (P < 0.05) in CK and CF. Also, the correlations of soil hydrolysable N and available P to soil microbial and enzymatic activities were highly significant (P < 0.01). Thus, to alter the traditional Chinese fir monoculture so as to mimic the natural forest conditions, managing mixed stands of Chinese fir and broadleaf trees or conducting crop rotation of conifers and broadleaf trees as well as minimizing forest disturbances like clear-cutting, slash burning and soil preparing, could be utilized.     

Screening for Nitrogen‐Use Efficiency in Potato with a Recirculating Hydroponic System

Abstract

Development of nitrogen (N)‐use‐efficient genotypes could reduce N fertilization and nitrate leaching; however, screening in field trials can be costly and time consuming. This study evaluated a rapid and economical methodology for screening of potato (Solanum tuberosum L.) cultivars for N‐use efficiency. A hydroponic experiment was conducted with two solution NO₃ ^? concentrations (0.05 and 1.0 mM) and five potato cultivars (Atlantic, Chieftain, Red Pontiac, Russet Norkotah, and Shepody). Plants were harvested 30 days after transplanting. Root dry weight in combination with plant N accumulation was considered as a good indicator of N uptake efficiency in low solution NO₃ ^? concentration. Plant total dry weight (TDW) and plant N accumulation (PN) were highly correlated; therefore, TDW can be considered as an alternative criterion for PN when screening for N‐uptake efficiency. Chieftain had high N‐uptake efficiency and high N‐utilization efficiency whereas Russet Norkotah had low N‐uptake efficiency.