Long‐term after‐effects of fertilisation on the restoration of calcareous grasslands

Question: What are the long‐term implications of former fertilisation for the ecological restoration of calcareous grasslands? Location: Gerendal, Limburg, The Netherlands. Methods: In 1970, ten permanent plots were established in just abandoned agricultural calcareous grassland under a regime of annual mowing in August. From 1971 to 1979, two different fertiliser treatments were applied twice a year to a subset of the plots (artificial fertiliser with different proportions of nitrogen and phosphorus). The vegetation of the plots was recorded yearly and vegetation biomass samples were taken for peak standing crop and total amounts of nitrogen, phosphorus and potassium. Species composition and floristic diversity were analysed over the research period (1970–2006) and between the treatments, including the use of multivariate techniques (Detrended Correspondence Analysis). Results: In terms of species number, there is a clear optimum 10 to 20 years after fertilisation has been terminated. Afterwards, there is a slow decrease; no new species appear and species of more nutrient‐rich conditions gradually disappear. For the fertilised plots that received a relatively high proportion of N, effects are found only in the first years, whereas, for the plots that received a relatively high proportion of P, long‐term after‐effects are found in species composition, peak standing crop, total amounts of phosphorus in biomass, and in soil phosphorus data. Conclusions: The effect of artificial fertiliser with a large amount of nitrogen disappears in less than ten years when mown in August, including removal of the hay. This is a promising result for restoration of N‐enriched calcareous grasslands, as the applied dose of nitrogen in this experiment largely exceeds the extra input of nitrogen via atmospheric deposition. Application of fertiliser with a large amount of phosphorus, however, has effects even more than 25 years after the last addition. There are no prospects that this effect will become reduced in the near future under the current mowing management.     

Effects of added nitrogen on leaf nitrogen concentration and population dynamics of insects associated with Rumex obtusifolius L.

A series of experiments was designed to study the effects of changes in leaf nitrogen (N) concentration on population dynamics of a range of insects associated with Rumex obtusifolius. During the study period, the N concentration in leaves fluctuated between 2 and 6% dry weight. The insects at both study sites showed a pattern of shift in time for peak population density (time‐shift). This suggests that the insect community dynamics might be closely related to the allocation and distribution of resources by the host‐plant. The elevated N concentration in the host‐plant did not change the temporal order of the peak population densities of the insects, although it may determine the time for the optimal exploitation of resources by each insect species.     

Behaviour of Heterodera zeae under stress of host nutritional status in Egypt

Studies on the effect of N, P and/or K fertilisers applied to Giza 2 corn, on behaviour of Heterodera zeae revealed that the nematode population greatly varied according to the fertiliser type and level. When N, P or K were used separately, the fertilised plants sustained the lowest nematode final population and the rate of build-up as compared with those of the control plants; however, the recommended levels of these fertilisers caused the lower values amongst the applied fertilisers levels and achieved an higher increase in the plant growth parameters. As for, the N, P and K used in different combinations, a similar trend was noticed when the recommended levels of the fertilisers were applied to plants. It is worthy to notice that when phosphorus was decreased or nitrogen increased each in combination with the other elements at their recommended levels, the nematode reproduced well and folded several times.     

More is not necessarily better: the impact of limiting and excessive nutrients on herbivore population growth rates

Abstract 1. The body tissues of insect herbivores contain higher concentrations of nitrogen and phosphorus than do their host plants, leading to an elemental mismatch that can limit herbivore growth, fecundity and ultimately influence population dynamics. While low nutrient availability can limit herbivore growth and reproduction, nutrient levels that exceed an organism’s nutritional requirements, i.e. an organisms’ threshold elemental ratio, can also decrease performance. 2. We conducted a laboratory experiment to examine the impacts of nitrogen and phosphorus additions on population growth rates of a phloem‐feeding insect herbivore. 3. Herbivore per capita population growth rates were highest at intermediate foliar nitrogen concentrations, indicating a performance cost on the highest nitrogen foliage. While there was no direct effect of foliar phosphorus concentration on insect performance, there was a strong and unexpected indirect effect. High soil phosphorus availability increased both foliar nitrogen concentrations and aphid tissue nitrogen, resulting in low population growth rates when both soil nitrogen and phosphorus availabilities were high. 4. In this study, experimental increases in foliar nitrogen levels led to a decrease in herbivore performance suggesting that excessive nutrient levels can limit herbivore population growth rates.     

Biomarkers of oxidative stress in Biomphalaria alexandrina snails for assessing the effects of certain inorganic fertilisers

Freshwater snails are often used to monitor aquatic pollution. The present study aims to use Biomphalaria alexandrina snails as bio-indicators for three types of NPK fertilisers (high nitrogen, high phosphorus and balanced). Data showed that high phosphorus and high nitrogen fertilisers have a negative impact on the growth rate of juvenile snails. Such observations were supported by determining antioxidant parameters in the digestive gland. Results indicated a significant increase in the catalase activity of snails that were exposed to ½ LC₅₀ concentrations of balanced and high phosphorus fertilisers. Meanwhile, the glutathione S-transferase, glutathione peroxidase and reduced glutathione parameters showed varying results representing an increase or decrease in the activities of all treated groups after both the first and second weeks, according to the type of fertiliser the snails were exposed to.     

Effect of organic fertilisers on the greening quality, shoot and root growth, and shoot nutrient and alkaloid contents of turf-type endophytic tall fescue, Festuca arundinacea

Increasing concern about the potential negative environmental impact of chemical fertilisers used in urban landscapes has provided impetus to develop organic fertilisers. However, little is known about the effect of organic fertilisers on turfgrass quality, growth and stress resistance. This study compared the effect of 11 organic fertilisers, applied at manufacturer's recommended rates, on greening quality, shoot and root growth, and shoot nutrient (an indication of nutrient uptake) and alkaloid content (an indication of insect resistance) in endophytic (infected with the fungus Neotyphodium coenophialum) tall fescue in the greenhouse. We measured turfgrass greening quality on a 1–9 scale weekly (9 being the highest), shoot and root growth monthly, and shoot contents of macro- and micronutrients and of various alkaloids at the end of 4 months. The results show that Corn Gluten and Cockadoodle Doo produce the highest turfgrass greening quality and shoot growth. Nature's Touch with enzymes enhanced root growth, and thus resulted in high root:shoot ratio, especially in third and fourth months after application. Compared with the most commonly used chemical fertiliser, Scott's Turf Builder, the organic fertilisers Cockadoodle Doo, Corn Gluten and Nature's Touch with enzymes generally resulted in better turf greening quality. Although Cockadoodle Doo, Vigoro and Scott's Turf Builder resulted in higher macronutrient contents in turfgrass shoots, there was no significant correlation between the nutrient contents in the fertilisers and in the shoots four months after application. Significant differences were found for all measured alkaloids in turfgrass shoots among the 13 treatments, and these differences varied with fertiliser. Overall, organic fertilisers produced higher turfgrass greening quality, root and shoot growth and insect resistance capacity (alkaloid content) compared with the chemical fertiliser, Scott's Turf Builder. On the basis of the high to excellent turfgrass greening quality ratings, root:shoot ratio, shoot nutrient and alkaloid contents in this study, we conclude that Cockadoodle Doo, Vigoro and Nature's Touch with enzymes are relatively superior organic fertilisers.     

Fertilisation practice changes rhizosphere microbial community structure in the agroecosystem

Rhizosphere microbial community is important for the acquisition of soil nutrients and closely related to plant species. Fertilisation practice changed soil quality. With the hypothesis of stronger rhizosphere effect of plant on rhizosphere microbial community than fertilisation management, we designed this research based on a long‐term field experiment (1982–present). This study consists of no fertilisation (NF), mineral fertilisers (NPK), mineral fertilisers plus 7,500 kg/ha of wheat straw addition (WS) and mineral fertilisers plus 30,000 kg/ha of cow manure (CM). After analysing, we found that fertilisation management not only elevated crop yield but also affected crop rhizosphere microbial community structure. The influence of fertilisation practice on wheat rhizosphere microbial structure was stronger than that of wheat. For wheat rhizosphere bacterial community, it was significantly affected by soil water content (SWC), nitrogen (TN), phosphorus (TP), pH, available phosphorus (AVP) and nitrogen (AVN), dissolved organic nitrogen (DON) and carbon (DOC). Besides SWC, pH, AVP, AVN, TN, TP and DOC, the wheat rhizosphere fungi community was also significantly affected by soil organic matter (SOM) and available potassium (AVK). Moreover, compared to rhizosphere bacterial community, the influences of soil physiochemical properties on rhizosphere fungal community was stronger. In conclusion, fertilisation practice was the primary factor structuring rhizosphere microbial community by changing soil nutrients availabilities in the agroecosystem.     

Susceptibility and tolerance in hybrid and pure‐line rice varieties to herbivore attack: biomass partitioning and resource‐based compensation in response to damage

Hybrid rice has been noted for its susceptibility to insects and diseases compared to pure‐line (conventional) rice varieties. We investigated herbivory by Nilaparvata lugens, Sogatella furcifera and Scirpophaga incertulas on replicated three‐line hybrid sets (parental and hybrid lines) in field and greenhouse experiments. In a field experiment, caterpillar densities and stemborer damage was similar among hybrid and parental lines. In field and greenhouse experiments, the cytoplasmic male sterile (CMS)‐lines and maintainer lines had higher densities of planthoppers (including N. lugens and S. furcifera) than restorer or hybrid lines likely because of their wild abortive CMS‐lineage. High nitrogen levels increased plant mortality due to N. lugens, but often reduced mortality from S. furcifera and S. incertulas: this was similar between hybrid and pure‐line varieties. The hybrids were generally more tolerant of herbivory (lower biomass reductions per unit weight of insect) than the inbred parental lines. The addition of nitrogen to both the hybrid and pure‐line varieties had contrasting effects on tolerance depending on the nature of the attacking insect: fertiliser increased tolerance to S. furcifera (lower losses of yield and shoot biomass per mg insect) and S. incertulas (lower yield, shoot and root biomass loss) but fertiliser reduced tolerance to N. lugens (higher loss of root biomass and no effects on yield and shoot biomass loss). Our results indicate that hybrid rice is not physiologically more susceptible to herbivores than are pure‐line varieties even under high nitrogen conditions, but does have higher tolerance to insect damage.     

Effect of soil-applied complex fertiliser on an insect–host plant relationship: Liriomyza trifolii on Solanum tuberosum

Insects respond to very low levels of nutritional and non‐nutritional compounds in plants, which influence their acceptance and colonisation of the plant or plant part, and thereby their growth and development. Plant nutrient levels can vary within and between plants, and are influenced by external factors such as fertiliser treatments, irrigation regime, and light. Soil levels of nitrogen, potassium, phosphorus, calcium, and magnesium can have significant effects on the amounts of these nutrients in the plant, and thereby on pest infestation. This study reports on the influence of seven different NPK fertiliser rates in potted potato (Solanum tuberosum cv. Mondial) plants on the nitrogen, phosphorus, potassium, calcium, and magnesium levels in the leaves, and the concomitant influence on infestation by, and development of, the serpentine leafminer, Liriomyza trifolii Burgess (Diptera: Agromyzidae). Results showed that increases in nitrogen in the potato leaves increased larval and pupal survival, and pupal and adult body weight and length. Potassium and phosphorus, on the other hand, decreased the host suitability of potato plants to L. trifolii, and were detrimental to the pest.     

Dietary phosphorus affects the growth of larval Manduca sexta

Although phosphorus has long been considered an important factor in the growth of diverse biota such as bacteria, algae, and zooplankton, insect nutrition has classically focused on dietary protein and energy content. However, research in elemental stoichiometry has suggested that primary producer biomass has similar N:P ratios in aquatic and terrestrial systems, and phosphorus-rich herbivores in freshwater systems frequently face phosphorus-limited nutritional conditions. Therefore, herbivorous insects should also be prone to phosphorus limitation. We tested this prediction by rearing Manduca sexta larvae on artificial and natural (Datura wrightii leaves) diets containing varying levels of phosphorus (approximately 0.20, 0.55, or 1.2% phosphorus by dry weight). For both artificial and natural diets, increased dietary phosphorus significantly increased growth rates and body phosphorus contents, and shortened the time to the final instar molt. Caterpillars did not consistently exhibit compensatory feeding for phosphorus on either type of diet. The growth and body phosphorus responses were not explicable by changes in amounts of potassium or calcium, which co-varied with phosphorus in the diets. Concentrations of phosphorus in D. wrightii leaves collected in the field varied over a range in which leaf phosphorus is predicted to affect M. sexta's growth rates. These results suggest that natural variation in dietary phosphorus is likely to affect the growth rate and population dynamics of M. sexta, and perhaps larval insects more generally.     

What do we know about biological nitrogen fixation in insects? Evidence and implications for the insect and the ecosystem

Many insects feed on a low‐nitrogen diet, and the origin of their nitrogen supply is poorly understood. It has been hypothesized that some insects rely on nitrogen‐fixing bacteria (diazotrophs) to supplement their diets. Nitrogen fixation by diazotrophs has been extensively studied and convincingly demonstrated in termites, while evidence for the occurrence and role of nitrogen fixation in the diet of other insects is less conclusive. Here, we summarize the methods to detect nitrogen fixation in insects and review the available evidence for its occurrence (focusing on insects other than termites). We distinguish between three aspects of nitrogen fixation investigations: (i) detecting the presence of potential diazotrophs; (ii) detecting the activity of the nitrogen‐fixing enzyme; and (iii) detecting the assimilation of fixed nitrogen into the insect tissues. We show that although evidence from investigations of the first aspect reveals ample opportunities for interactions with potential diazotrophs in a variety of insects, demonstrations of actual biological nitrogen fixation and the assimilation of fixed nitrogen are restricted to very few insect groups, including wood‐feeding beetles, fruit flies, leafcutter ants, and a wood wasp. We then discuss potential implications for the insect's fitness and for the ecosystem as a whole. We suggest that combining these multiple approaches is crucial for the study of nitrogen fixation in insects, and argue that further demonstrations are desperately needed in order to determine the relative importance of diazotrophs for insect diet and fitness, as well as to evaluate their overall impact on the ecosystem.     

Uptake of zinc and phosphorus by plants is affected by zinc fertiliser material and arbuscular mycorrhizas

Background and Aims

Water solubility of zinc (Zn) fertilisers affects their plant availability. Further, simultaneous application of Zn and phosphorus (P) fertiliser can have antagonistic effects on plant Zn uptake. Arbuscular mycorrhizas (AM) can improve plant Zn and P uptake. We conducted a glasshouse experiment to test the effect of different Zn fertiliser materials, in conjunction with P fertiliser application, and colonisation by AM, on plant nutrition and biomass.

Methods

We grew a mycorrhiza-defective tomato genotype (rmc) and its mycorrhizal wild-type progenitor (76R) in soil with six different Zn fertilisers ranging in water solubility (Zn sulphate, Zn oxide, Zn oxide (nano), Zn phosphate, Zn carbonate, Zn phosphate carbonate), and supplemental P. We measured plant biomass, Zn and P contents, mycorrhizal colonisation and water use efficiency.

Results

Whereas water solubility of the Zn fertilisers was not correlated with plant biomass or Zn uptake, plant Zn and P contents differed among Zn fertiliser treatments. Plant Zn and P uptake was enhanced when supplied as Zn phosphate carbonate. Mycorrhizal plants took up more P than non-mycorrhizal plants; the reverse was true for Zn.

Conclusions

Zinc fertiliser composition and AM have a profound effect on plant Zn and P uptake.     

Effects of insect attack to stems on plant survival,growth, reproduction and photosynthesis

Studies of insect herbivory have mostly focused on leaf‐feeding even though most woody plant biomass is stem tissue. Attack to stems has the potential to be more detrimental to plant performance than attack to leaves. Here we asked how severe is the impact of insect stem herbivory on plant performance. We quantify the effect of insect stem herbivory via a meta‐analysis of 119 papers in 100 studies (papers by the same authors were treated as the same study). These studies involved 92 plant species and 70 species of insect herbivore (including simulated herbivory). Attack to plant stems reduced plant performance by an average of approximately 22%. Stem herbivory had greatest impacts on plant and branch survival, which was reduced by 63%. Measures of plant reproduction and vegetative biomass were reduced by 33% and 16% respectively, while measurements of photosynthetic rate were not significantly different between plants with and without stem herbivore attack. Stem herbivory led to a decline in leader performance but an increase in performance of laterals, highlighting the importance of plant compensation. Juvenile plants were more severely affected by stem herbivory than adult plants, and studies conducted in greenhouses found more severe effects than studies conducted in the field. Stem herbivory did not have a significant effects on any of the non‐performance responses measured (defence compounds, SLA, root:shoot, phenology and plant carbon and nitrogen). We compare our results with results from various meta‐analyses considering herbivory on other plant parts. The impact of insect herbivory to stems on plant performance appears at least as severe as insect herbivory to roots and leaves, if not more.     

Manure application improves both bumblebee flower visitation and crop yield in intensive farmland

Pollinators provide vital ecosystem services across croplands, yet simultaneously they are influenced by agricultural practices. Nevertheless, only a few studies have explored the potential interactions between soil fertilisers and pollinators. The aim of the current study, which was carried out in Poland in 2015, was to investigate the effect of different fertiliser regimes on bumblebee flower visitation rate and seed yield in crops of the field bean (Vicia faba L.). Our results show that the number of bumblebee visits may be affected by the choice of crop fertiliser. We detected differences in bumblebee number between fertiliser treatments. The organic fertiliser (manure) treatment resulted in the highest bumblebee visitation, although this did not differ significantly from NP, no fertiliser and NK treatments. On the other hand, we observed lower numbers of bumblebees on field bean plots treated with N, NPK, and PK inorganic fertilisers. Manure application also boosted plant height and resulted in a high yield similar to other balanced fertilisers (NPK and PK). Therefore, manure was the only fertiliser that resulted in a high field bean yield and at the same time attracted the main pollinators of the crop. Thus, we suggest that appropriate management practices influence both plant growth and also pollination services and we show that modern agriculture can make compromise between effectiveness and nature conservation.     

Tritrophic effects of organic and conventional fertilisers on a cereal‐aphid‐parasitoid system

The impact of parasitoids on pests varies between conventional and low‐intensity agricultural systems. Although the impacts on parasitoid natural enemies of many practices within these agricultural systems are well understood, the role of fertilisers has been less well studied. The effects of organic‐based and conventional fertilisers on Hordeum vulgare L. (Poaceae), the aphid Metopolophium dirhodum Walker (Hemiptera: Aphididae), and its parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae) was investigated using cage release experiments and measures of aphid and parasitoid fitness were taken. Barley tiller number and aphid weight were increased by fertilisers, particularly under conventional treatments. Adult parasitoid size correlated positively with that of the host, M. dirhodum, whereas percentage parasitism was not affected by fertiliser treatment or host size. The results suggest that the increased parasitoid impact observed in some low‐intensity or organic systems is not a direct result of fertiliser treatment. Our results indicate that fertiliser treatments that improve cereal‐aphid fitness will improve parasitoid fitness as measured by parasitoid size but may not influence percentage parasitism.     

Effects of organic and inorganic fertilisers on mosquito populations in rice fields of southern India

The effects of nitrogenous (inorganic) fertilisers, organic manures and blue-green algae (BGA) biofertiliser on mosquito populations (Diptera: Culicidae) were studied in rice fields of Madurai, Tamil Nadu, south India, with particular attention to Culex vishnui Theobald, Cx. pseudovishnui Colless and Cx. tritaeniorhynchus Giles, the vectors of Japanese encephalitis (JE). The application of urea, a nitrogenous fertiliser, in rice fields significantly increased the grain yield and the population densities of mosquito larvae and pupae (anophelines as well as culicines) in a dose-related manner. Fields treated with inorganic fertilisers (N, P, K) had significantly higher population densities of mosquito immatures than fields treated with organic manures (farmyard manure and green manure). Without nitrogenous fertiliser, BGA increased paddy yield without enhancing mosquito production. Therefore, the use of BGA with less nitrogenous fertiliser is recommended, which is beneficial economically and agronomically to the farming community and also significantly reduces mosquito production in rice fields. Increased use of nitrogenous fertiliser over the past two decades may have contributed to the increased severity of Japanese encephalitis epidemics, vectors of which breed in rice fields.     

Spatial variation of soil quality and pollution assessment of heavy metals in cultivated soils of Henan Province,China

Abstract

Eight chemical and physical characteristics and seven biological properties of the soils from five cultivated areas in the Henan Province were quantified. Concentrations of Cu, Cr, Zn and Mn were determined using the flame atomic absorption spectrometry. In addition available phosphorus, chloride, soluble salt and pH were measured. The activities of enzymes were determined by a literature method. The results showed that the concentrations of Mn, Zn and Cr had close relationships with that of available phosphorus, and their concentrations increased with the prolonged application of organic and mineral fertilisers and pesticides-fungicides. The activities of cellulase have a relationship to the concentrations of Zn and Mn at 0.95 levels respectively, Zn and Mn stimulate many enzyme activities. The relationship between protease and available phosphorus was nearly distinctive at 0.95 levels, relating with the use of nitrogen fertiliser in the farmlands. Local organic manures and urea fertilisers did not change the soil characteristics to a great extent. However, the soils showed moderate and moderate-to-strong contamination by Mn and Zn in the study areas. Wastewater and groundwater irrigation, pesticides-fungicides, and fertiliser may be responsible for the elevated concentrations of Zn and Mn in the soil samples.     

Effects of nitrogen deposition and insect herbivory on patterns of ecosystem-level carbon and nitrogen dynamics: results from the CENTURY model

Atmospheric nitrogen deposition may indirectly affect ecosystems through deposition-induced changes in the rates of insect herbivory. Plant nitrogen (N) status can affect the consumption rates and population dynamics of herbivorous insects, but the extent to which N deposition-induced changes in herbivory might lead to changes in ecosystem-level carbon (C) and N dynamics is unknown. We created three insect herbivory functions based on empirical responses of insect consumption and population dynamics to changes in foliar N and implemented them into the CENTURY model. We modeled the responses of C and N storage patterns and flux rates to N deposition and insect herbivory in an herbaceous system. Results from the model indicate that N deposition caused a strong increase in plant production, decreased plant C : N ratios, increased soil organic C (SOC), and enhanced rates of N mineralization. In contrast, herbivory decreased both vegetative and SOC storage and depressed N mineralization rates. The results suggest that herbivory plays a particularly important role in affecting ecosystem processes by regulating the threshold value of N deposition at which ecosystem C storage saturates; C storage saturated at lower rates of N deposition with increasing intensity of herbivory. Differences in the results among the modeled insect herbivory functions suggests that distinct physiological and population response of insect herbivores can have a large impact on ecosystem processes. Including the effects of herbivory in ecosystem studies, particularly in systems where rates of herbivory are high and linked to plant C : N, will be important in generating accurate predictions of the effects of atmospheric N deposition on ecosystem C and N dynamics.     

The effect of increased nitrogen load on phytoplankton in a phosphorus‐limited lake

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When do herbivorous insects compete? A phylogenetic meta‐analysis

When herbivorous insects interact, they can increase or decrease each other's fitness. As it stands, we know little of what causes this variation. Classic competition theory predicts that competition will increase with niche overlap and population density. And classic hypotheses of herbivorous insect diversification predict that diet specialists will be superior competitors to generalists. Here, we test these predictions using phylogenetic meta‐analysis. We estimate the effects of diet breadth, population density and proxies of niche overlap: phylogenetic relatedness, physical proximity and feeding‐guild membership. As predicted, we find that competition between herbivorous insects increases with population density as well as phylogenetic and physical proximity. Contrary to predictions, competition tends to be stronger between than within feeding guilds and affects specialists as much as generalists. This is the first statistical evidence that niche overlap increases competition between herbivorous insects. However, niche overlap is not everything; complex feeding guild effects indicate important indirect interactions.