Outdoor Pot Trial Research Articles

Mixed Cropping as Affected by Phosphorus and Water Supply

In a future exposed to threats of climate change, sustainable biomass production will be crucial. Maize (Zea mays) and sorghum (Sorghum sp.) are important crops for human and animal nutrition, as well as for bioenergy. The aim of this study was to investigate maize and sorghum in mixed cropping with soybean (Glycine max) and faba bean (Vicia faba) regarding biomass yield, drought tolerance, phosphorus (P) availability, and enzyme activity in soil as affected by the single and combined effects of water and P supply in two outdoor pot trials with rainout shelters. Maize had the highest biomass under sufficient water supply (80% water holding capacity, WHC), but a sharp decrease of its biomass of about 60% was measured when water was limited (30% WHC). In the mixtures, drought induced reduction of biomass was less than 40%. For mixed cropping usually higher contents of labile P fractions in soil than for sole cropped monocots were found. This was especially true for the combined stress of water and P deficit and can be partly explained by a higher activity of the acid phosphatase in the soil of the mixtures. A higher yield stability of the crop mixtures makes them a suitable agronomic alternative to sole cropped maize or sorghum under suboptimal conditions of water and P shortage.

Formulation and stabilization of an Arthrobacter strain with good storage stability and 4-chlorophenol-degradation activity for bioremediation

Chlorophenols are widespread and of environmental concern due to their toxic and carcinogenic properties. Development of less costly and less technically challenging remediation methods are needed; therefore, we developed a formulation based on micronized vermiculite that, when air-dried, resulted in a granular product containing the 4-chlorophenol (4-CP)-degrading Gram-positive bacterium Arthrobacter chlorophenolicus A6. This formulation and stabilization method yielded survival rates of about 60% that remained stable in storage for at least 3 months at 4 °C. The 4-CP degradation by the formulated and desiccated A. chlorophenolicus A6 cells was compared to that of freshly grown cells in controlled-environment soil microcosms. The stabilized cells degraded 4-CP equally efficient as freshly grown cells in two different set-ups using both hygienized and non-treated soils. The desiccated microbial product was successfully employed in an outdoor pot trial showing its effectiveness under more realistic environmental conditions. No significant phytoremediation effects on 4-CP degradation were observed in the outdoor pot experiment. The 4-CP degradation kinetics from both the microcosms and the outdoor pot trial were used to generate a predictive model of 4-CP biodegradation potentially useful for larger-scale operations, enabling better bioremediation set-ups and saving of resources. This study also opens up the possibility of formulating and stabilizing also other Arthrobacter strains possessing different desirable pollutant-degrading capabilities.

Optimal pre-plant irrigation and fertilization can improve biomass accumulation by maintaining the root and leaf productive capacity of cotton crop

Cotton is a major cash crop grown worldwide primarily for fiber and oil seed. As the most important cultural practices for cotton production, single pre-plant irrigation and basal fertilization for cotton plant growth and yield are well documented, but their coupling effects are poorly understood in arid regions. A 2-year outdoor pot trial was conducted to unravel the effects of pre-plant irrigation and basal fertilization on leaf area, root growth, biomass accumulation, and capacity of leaf area and root in cotton plant. Two pre-plant irrigations (i.e., W80, well-watered and W0, not watered) and two basal dressing fertilizations (F10, surface application and F30, deep application) were used in the experiments. The aboveground and reproductive biomass were highest in W80F10 after 69 days after emergence. Furthermore, W80F10 increased the root length in the 0–40 cm soil layer and the leaf area and improved the loading boll capacity of the effective root length and leaf area. The effective root length and leaf area had substantial direct effects on the aboveground and root biomass, respectively. Our data suggest that basal fertilizer surface application under adequate pre-plant irrigation is an effective strategy for optimal cotton production, which improves the coordination of water-nutrient absorption and photosynthetic areas and promotes assimilated distribution to the reproductive structures.

Biological control of yellow rust of wheat (Puccinia striiformis) with Serenade®ASO (Bacillus subtilis strain QST713)

Yellow rust (Puccinia striiformis f. sp. tritici) is an important disease in wheat causing significant yield reductions, if not effectively controlled. The biofungicide Bacillus subtilis strain QST 713 suspension concentrate (Serenade®ASO) was investigated for its potential for yellow rust control in winter wheat field trials. Serenade®ASO reduced severity of yellow rust significantly, providing up to 60% control at BBCH growth stage 65–69, under moderate disease pressure. Under high disease pressure reductions were more variable and provided less than 30% control. An increase in the number of applications of biofungicide from two to four per season tended to improve disease control, although differences were not always significant. With a few exceptions no clear dose-response was seen between using 1, 2, 4, 6 or 8 l/ha applied 4 times at 8–10-day intervals. Yield responses were positive, but responses to biofungicide were only significant in a few cases, and in all cases the level of control and yield responses were significantly lower compared with using prothioconazole as chemical control. An outdoor pot trial using artificial inoculation tested preventive and curative application of Serenade®ASO at three dose rates. This trial confirmed the lack of a clear dose response but showed that timing had a major impact on control, with the best control obtained at the day of inoculation. This study revealed that Serenade®ASO cannot stand alone in the control of yellow rust. More research is needed to develop integrated disease management strategies which also include biofungicides.

Temperature and Light Requirements for Germination and Emergence of Three Arable Papaveraceae Species

This research investigated the temperature and light requirements for seed germination and emergence patterns of pinnate poppy, violet horned-poppy, and nodding hypecoum, three annual Papaveraceae species found in arable lands in the Mediterranean region. Two experiments performed in growth chambers (1) analyzed light (complete darkness or 12 h light) and temperature (10/5, 15/5, and 20/10 C day/night temperatures) requirements for germination, and (2) determined base temperature (Tb) for germination. An outdoor pot trial was also set up to study emergence patterns. All species showed higher germination in complete darkness than they did with a light regime, irrespective of dormancy level, time of the year, and temperature regime under which germination was tested, illustrating better germination when seeds are buried.Tbranged from −2.6 to 0 C, depending on the species, indicating low temperature requirements for germination. Given their higher germination in daily fluctuating, rather than constant temperatures, the three Papaveraceae species should have the capacity to form persistent seed banks. These species behaved as winter annuals (from November to February) in the pot experiment and had difficulties to emerge in spring. Given that they cannot avoid autumn–winter chemical treatments, this could partially explain their regression in arable fields. These results bring new information to develop management strategies for these Papaveraceae species in agroecosystems.

Waste recovered by‐products can increase growth of grass–clover mixtures in low fertility soils and alter botanical and mineral nutrient composition

AbstractThe effectiveness of four by‐products (biogas digestate, pot ale, rockdust and wood ash) as fertilisers of a perennial ryegrass (Lolium perenne)–red clover (Trifolium pratense) mixture in terms of biomass production, botanical composition and macro‐ and micronutrient concentrations was tested in an outdoor pot trial. This was carried out over two growing seasons using two inherently low‐fertility soils used for forage production. Macro‐ and micronutrients (N, P, K, Ca, Mg, Co, Cu, Mn, Mo and Zn) relevant for crops and livestock were determined in soils and plants. All the by‐products increased overall biomass production and affected nutrient concentrations of the individual plant species to varying degrees. In addition the competitive balance between grass and clover was altered leading to different botanical composition in the different treatments and consequently differences in the nutrient concentrations of the species mixture. Changes were due to the nutrients applied in the by‐products per se and/or to changes in the soil chemistry caused by the by‐products. The results suggest a potential to enhance agricultural productivity through improved production and quality of forage on less fertile land by matching of by‐products and soil properties.

Fertilizer 15N Accumulation, Recovery and Distribution in Cotton Plant as Affected by N Rate and Split

N fertilization of 300 kg N ha−1 is normally applied to cotton crops in three splits: pre-plant application (PPA, 30%), first bloom application (FBA, 40%) and peak bloom application (PBA, 30%) in the Yangtze River Valley China. However, low fertilizer N plant recovery (NPR) (30-35%) causes problems such as cotton yield stagnation even in higher N rate, low profit margin of cotton production and fertilizer release to the environment. Therefore, it is questioned: Are these three splits the same significance to cotton N uptake and distribution? An outdoor pot trial was conducted with five N rates and 15N labeled urea to determine the recovery and distribution of 15N from different splits in cotton (Gossypium hirsutum L. cv. Huazamian H318) plant. The results showed that, cotton plant absorbed fertilizer 15N during the whole growing period, the majority during flowering for 18-20 d regardless of N rates (150-600 kg ha−1). Fertilizer 15N proportion to the total N accumulated in cotton plant increased with N rates, and it was the highest in reproductive organs (88% averaged across N rates) among all the plant parts. FBA had the highest NPR (70%), the lowest fertilizer N lose (FNL, 19%), and the highest contribution to the fertilizer 15N proportion to the total N (46%) in cotton plant, whereas PPA had the reverse effect. It suggests that FBA should be the most important split for N absorption and yield formation comparatively and allocating more fertilizer N for late application from PPA should improve the benefit from fertilizer.

Effect of Potassium Application Rate on Cotton (Gossypium hirsutum L.) Biomass and Yield

Cotton production in China is recently confronted with either yield loss by plant early senescence resulted from potassium (K) deficit, or cost rise and nutrients leaching by K excess use. However, the optimal K rate in term of cotton biomass production and yield remains uncertain to make a recommendation for the farmers. Both field with random block design and outdoor pot trials were carried out to determine how cotton (Gossypium hirsutum L. vs. Huazamian H318) biomass and yield were affected by K rates. The result showed that K2 (225 kg ha–1) harvested the highest yield (1 341 kg ha–1) and bore the most bolls (74 bolls per square meter) in the field trial, with a similar trend for the pot trial. As expected, cotton biomass of K2 was the highest at each of the sampling stages, especially for reproductive organs. Cotton biomass initiated simultaneously the fast accumulation period (FAP), but terminated the period differently among five K rates (0–450 kg ha–1). During the period, K2 had the highest biomass accumulation rate both on an average and in the maximum, and for vegetative and reproductive organs. It suggests that K rate of 225 kg ha–1 be optimal to produce a favorable yield in the field of medium fertility when N 300 kg ha–1 and P2O5 90 kg ha–1 are applied in the Middle Reaches of Yangtze River, in which condition cotton plants accumulate greater amount of biomass with a higher accumulating rate.

Pilot scale ex-situ bioremediation of heavily PAHs-contaminated soil by indigenous microorganisms and bioaugmentation by a PAHs-degrading and bioemulsifier-producing strain

This study aims at the remediation of heavily PAH-contaminated soil containing 375mg of total PAHs per kilogram dry soil. Pilot scale bioremediation experiments were carried out by three approaches with contaminated soil from abandoned sites of Beijing Coking Plant using outdoor pot trials. The first approach was bioaugmentation with a bacterial strain which degrades PAH and produces bioemulsifier, the second approach comprised of biostimulation of indigenous microorganisms with supplementing nutrients and the last approach involved the combination of both biostimulation and bioaugmentation. An on-site land farming group was set as a control in which the total PAHs and 4–6 ring-PAHs were reduced by 23.4% and 10.1%, respectively after 175 days. Meanwhile, in the first approach group, the total PAHs and 4–6 ring-PAHs were reduced by 26.82% and 35.36%, respectively; in the second approach group both percentages were 33.9% and 11.0%, respectively; while in the third approach group, these pollutants were reduced by 43.9% and 55.0%, respectively. The results obtained suggested that biostimulation and bioaugmentation combined could significantly enhance the removal of PAHs in the contaminated soil.

Kinetics of Polycyclic Aromatic Hydrocarbon (PAH) Degradation in Long-term Polluted Soils during Bioremediation

Bioremediation experiments with ten different soil samples from former industrial sites which were long-term polluted with polycyclic aromatic hydrocarbons (PAHs) were carried out using outdoor pot trials. The degradation of 15 PAHs according to the US EPA was investigated for 168 weeks through repeated soil sampling and determination of the total PAH concentration. On average, degradation was largest for acenaphthene (88%; 63 to 99%) and smallest for anthracene (22%; no significant degradation to 89%). For most of the PAH single substances, degradation kinetics were characterised by a first initial phase of fast degradation. In a subsequent second phase, degradation diminished and residual PAH concentrations were approached within 168 weeks, resulting in a similar PAH pattern in the ten soil samples. Degradation kinetics was calculated through the selection of the appropriate differential rate equation from a set of seven equations. Kinetics of PAH degradation was best fitted by single and two coupled first order exponential equations with median R² of 0.71 (0.01 to 1.00). Degradation rate constants of the rapid phase (k 1) ranged from 0.05×10−2 week−1 for benzo[k]fluoranthene to 18.3 week−1 for naphthalene and for the subsequent slow degradation phase (k 2) they ranged from 0.01×10−2 week−1 for benzo[a]anthracene to 2.3×10−2 week−1 for fluoranthene. Degradation was governed by desorption and diffusion processes of different rates, while microbial activity did not influence the kinetics. Median disappearance times (DT50) ranged from 6.1 weeks for naphthalene to 522 weeks for benzo[k]fluoranthene. With the exception of the 6-ring PAHs dibenzo[ah]anthracene and indeno[1,2,3-cd]pyrene, this sequence followed the PAHs’ degree of condensation. The total initial PAH concentration and the residual concentration were correlated with R² of 0.69, with larger initial PAH concentrations leading to larger residual concentrations and degradation rates.

The effect of dazomet and fosetyl-Aluminium on indigenous and introduced arbuscular mycorrhizal fungi in commercial strawberry production

Field and outdoor pot trials were conducted to assess the compatibility of an introduced arbuscular mycorrhizal fungal (AMF) isolate Glomus fistulosum ([Skou and Jakobsen sp. nov.] BEG 31) and indigenous AMF isolate/s, with biocides frequently used in commercial strawberry production, namely dazomet and fosetyl-Al (fosetyl aluminium). In the field trial, ‘Elsanta’ plants did not exhibit any mycorrhizal colonisation by indigenous AMF spp. after soil fumigation with dazomet. Recolonisation by indigenous AMF was low one year after soil fumigation and was possibly as a result of viable indigenous AMF propagules being washed in from adjacent non-fumigated fields. The degree of colonisation by the introduced AMF isolate G. fistulosum decreased by approximately 1/2 of its original value after one year in the field. Despite fosetyl-Al application Phytophthora fragariae Hickman infection was still prevalent in ‘Elsanta’ during the trial. Although fosetyl-Al did not significantly affect mycorrhizal colonisation, % total G. fistulosum root length colonisation and the proportion of it that was arbuscular, significantly decreased with increased sampling time. In the pot trial, foliar applications of fosetyl-Al significantly reduced the percentage of AMF colonisation that was vesicular and this was independent of the number of spray applications. Fosetyl-Al did not significantly influence the metabolic activity of G. fistulosum colonisation.

Untersuchungen zur Aufnahme und Verteilung von Stickstoff bei alten und neuen deutschen Sommerweizensorten

Abstract Uptake and distribution of nitrogen in old and new German summer wheats Five old German summer wheat varieties, bred in the first third of this century, were compared with five new varieties in an outdoor pot trial. The modern genotypes had taken up slightly more N, both at anthesis and at maturity. At anthesis, N percentage in all organs was considerably higher for modern cultivars. This resulted mainly from a dilution effect caused by superior dry masses of old varieties. Modern genotypes accumulated more N in the upper leaves and ears. As compared with the old varieties, less N was found in the stems of the new cultivars. At maturity, N concentration in vegetative organs was simular for both groups of varieties. N percentage of grains was higher for old cultivars. However, the new genotypes achieved higher N yields. This resulted in part from the slightly higher assimilation of N. Moreover, new genotypes were superior in N translocation which was reflected by higher nitrogen harvest indexes. The postfloral loss of N from the vegetative tissue depended on the organ and the age of the varieties.

Untersuchungen zur Bildung und Verteilung der Biomasse bei alten und neuen deutschen Sommerweizensorten

Abstract Accumulation and distribution of dry matter in old and new german summer wheat‐cultivars Five old german summer wheat varieties bred in the first third of this century were compared with five new varieties in an outdoor pot trial. The new genotypes outyielded the old varieties by only approximately 10%. It may be supposed that this small genetic gain in grain yield resulted from breeding for superior bread‐making quality. The new genotypes produced more kernels per plant. The tkw of both groups of varieties was nearly equal. However, new and old varieties did not show a particular yield structure. The grain/straw‐ratio of the new varieties was higher. The old varieties reached anthesis later and had produced more above‐ground biomass at anthesis as well as at maturity. Whereas the old genotypes had higher stem and sheath weights at flowering, the weights and areas of leaf laminae were simular for old and new varieties. The new genotypes tended to greater upper leaves and had greener lower leaves, but did not gain more dry matter after anthesis. The postfloral loss of dry matter from the vegetative tissue depended on the organ and the age of the varieties.