Vertical and horizontal development of the root system of carrots following green manure

Cover crops grown as green manure or for other purposes will affect nitrogen (N) distribution in the soil, and may thereby alter root growth of a succeeding crop. During two years, experiments were performed to study effects of nitrogen supply by green manure on root development of carrots (Daucus carota L). Total root intensity (roots cm⁻² on minirhizotrons) was significantly affected by the green manures, and was highest in the control plots where no green manure had been grown. Spread of the root system into the interrow soil was also affected by green manure treatments, as the spread was reduced where spring topsoil N_min was high. Although N supply and distribution in the soil profile differed strongly among the treatments, no effect was observed on the rooting depth of the carrot crops. Across all treatments the rooting front penetrated at a rate of 0.82 and 0.68 mm day⁻¹ °C⁻¹ beneath the crop rows and in the interrow soil, respectively. The minirhizotrons only allowed measurements down to 1 m, and the roots reached this depth before harvest. Extrapolating the linear relationship between temperature sum and rooting depth until harvest would lead to rooting depths of 1.59 and 1.18 m under the crop rows and in the interrow soil respectively. Soil analysis showed that the carrot crop was able to reduce N_min to very low levels even in the 0.75 to 1.0 m soil layer, which is in accordance with the root measurements. Still, where well supplied, the carrots left up 90 kg N ha⁻¹ in the soil at harvest. This seemed to be related to a limited N uptake capacity of the carrots rather than to insufficient root growth in the top metre of the soil. This revised version was published online in June 2006 with corrections to the Cover Date.     

CO2 enrichment using CRAM fermentation improves growth,physiological traits and yield of cherry tomato (Solanum lycopersicum L.)

Carbon dioxide (CO₂) concentration in greenhouses is sub-optimal for vegetable production. Many techniques have been used to increase CO₂ concentration in greenhouses but most of them are expensive with certain limitations and drawbacks. We adopted a new strategy to elevate CO₂ concentration in the greenhouse throughout the day via crop residues and animal manure composting (CRAM). During the whole cultivation period, CRAM-treated greenhouse had doubled CO₂ concentration which significantly increased the yield of cherry tomatoes (Solanum lycopersicum L.), i.e., up to 38%. The influence of CRAM procedure on cherry tomato quality was also investigated and the concentrations of total soluble solids (TSS) and soluble sugar were found to be significantly higher in cherry tomatoes grown under composting greenhouse than that of non-composting greenhouse. Additionally, CRAM-CO₂ enrichment also resulted in increased concentrations of ascorbic acid (Vitamin C) and titrate acid as compared to control. In contrast, the concentration of nitrate was considerably decreased in cherry tomato grown under CO₂ enriched condition than that of control. The increase in active oxygen metabolisms such as POD, CAT and SOD while a decrease in MDA, as well as APX was observed for cherry tomatoes grown under CO₂ enriched condition. Hence, CO₂ fertilization by using CRAM in greenhouse significantly improved quality and increased the yield of cherry tomatoes.     

Induction of purple sulfur bacterial growth in dairy wastewater lagoons by circulation

Aims:  To determine whether circulation of dairy wastewater induces the growth of phototrophic purple sulfur bacteria (PSB).
Methods and Results:  Two dairy wastewater lagoons that were similar in size, geographic location, number and type of cattle loading the lagoons were chosen. The only obvious visual difference between them was that one was stagnant and the water was brown in colour (Farm 1), and the other was circulated and the water was red in colour because of the presence of PSB that contained carotenoid pigments (Farm 2). Both wastewaters were sampled monthly for 3 months and assayed for PSB and extractable carotenoid pigments (ECP). After this point, circulators were placed in the wastewater lagoon on Farm 1, and samples were taken monthly for 9 months and assayed for PSB and ECP. Before the installation of circulators, no PSB-like 16S rRNA sequences or ECP were observed in the wastewater from Farm 1; however, both were observed in the wastewater from Farm 2. After the installation of circulators, statistically greater levels of PSB and extractable carotenoid pigments were observed in the wastewater from Farm 1.
Conclusions:  Circulation enhances the growth of PSB in dairy wastewater.
Significance and Impact of this Study:  Because PSB utilize H₂S and volatile organic acids (VOA) as an electron source for photosynthesis, and VOA and alcohols as a carbon source for growth, the increase in these bacteria should reduce H₂S, volatile organic compounds and alcohol emissions from the lagoons, enhancing the air quality in dairy farming areas.     

Agronomic properties of a volcanic ash-derived soil as affected by uncomposted organic materials

A sandy soil from the Vesuvian volcanic area, low in organic matter, was treated in pot experiments with raw farm-yard manure, green horse bean and wheat straw in order to study the effects of organic amendments on physical, chemical and biological properties. Farm-yard manure, rawly composted, caused a significant decrease of bulk density and improved water retention and the content of available phospate and potassium. It also showed the higher conversion co-efficient to stable humus during two years of the incubation period. It depressed the wheat seed germination and cotyledon growth for a one-year incubation period. Horse bean green manure was rapidly mineralized and did not remarkably improve the physical properties of the soil. Furthermore, it produced the lowest humus content and negatively affected seed development for eight months, but remarkably increased nutrient elements' contents (P and K). Wheat straw, added with N (2% urea form), improved humus formation and soil structure compared to horse bean; it increased K and P content and negatively affected seedling development for two months only.     

Suppression of Meloidogyne chitwoodi with Sudangrass Cultivars as Green Manure

Meloidogyne chitwoodi race 1 reproduced on Piper sudangrass (Sorghum bicolor (L.) Moench), 332 (sudangrass hybrid), and P855F and P877F (sorghum-sudangrass hybrids), but failed to reproduce efficiently on Trudan 8, Trudex 9 (sudangrass hybrids), and Sordan 79, SS-222, and Bravo II (sorghum-sudangrass hybrids). Meloidogyne chitwoodi race 2 behaved similarly and reproduced more efficiently on Piper, P855F, and P877F than on Trudan 8, Trudex 9, or Sordan 79. The mean reproductive factor for M. chitwoodi races on the poorer hosts ranged from <0.1 to 0.9 under greenhouse and field conditions. Meloidogyne hapla failed to reproduce on any of the cultivars tested. In the laboratory, leaves of each cultivar chopped and incorporated as green manure reduced the M. chitwoodi population in infested soil more than unamended or wheat green manure treatments. Trudan 8, although limited to the zone of incorporation, protected this zone from colonization of upward migrating second stage juveniles (J2) for up to 6 weeks. Leaves of Trudan 8 but not roots were effective against M. chitwoodi, and J2 appeared to be more sensitive than egg masses. Trudan 8 and Sordan 79 as green manure reduced M. chitwoodi in bucket microplots under field conditions.     

Improvement of soil acidification and ammonium nitrogen content in tea plantations by long-term use of organic fertilizer

• Soil acidification is common in some Chinese tea plantations, which seriously affected growth of tea trees. Hence, it is essential to explore soil remediation in acidified tea plantations for sustainable development of the tea industry. We sought to determine how different fertilizers affect acidified soil and their N transformation in tea plantations.
• Different fertilizers were used on acidified tea plantation soils for 4 years (2017–2021), and changes in soil pH, indices related to soil N transformation and tea yield were analysed to construct interaction networks of these indices and find which had the largest influence on fertilization.
• Long-term use of sheep manure reduced soil acidification, increased soil pH, enhanced the number and intensity of N-fixing and ammonifying bacteria, urease, protease, asparaginase and N-acetamide glucose ribosidase activity and nifH gene expression. This treatment reduced the number and intensity of soil nitrifying and denitrifying bacteria, nitrate reductase and nitrite reductase activity, while the expression of amoA-AOA, nirK, nirS, narG and nosZ in turn increased ammonium N content of the soil, reduced nitrate N content, and enhanced tea yield. Topsis index weight analysis showed that ammonium N content in the soil had the largest impact among fertilization effects.
• Long-term use of sheep manure was beneficial in restoring the balance of the micro-ecosystem in acidified soil. This study provides an important practical basis for soil remediation and fertilizer management in acidified tea plantation soils.

     

Effects of addition of calcium and magnesium salts on ammonia volatilization during manure decomposition

Ammonia volatilization during aerobic decomposition of poultry manure was significantly reduced through additions of calcium and magnesium salts. The percentage reduction in ammonia loss decreased during the 48 day decomposition period from 85–100% in the first 2–3 weeks, to 23–52% at the end of the experiment. The maximum amount of ammonia which was retained (i.e. maximum reduction in ammonia loss) through addition of the chloride salts of Mg²⁺ or Ca²⁺ was independent of the type of cation. However, CaCl₂ released some of the ammonia initially retained as production of CO₂ and NH₃ from the manure decreased after 3 weeks of decomposition, whereas both MgCl₂ and MgSO₄ did not release any of the initially retained ammonia over the 7 week incubation period. Over the entire incubation period MgCl₂ therefore retained more ammonia than CaCl₂. Magnesium sulphate was considerably less effective in retaining ammonia than either chloride salts.     

Sulfide removal from livestock biogas by Azospirillum-like anaerobic phototrophic bacteria consortium

Biogas production from anaerobic biodegradation of livestock waste is a potential source of renewable energy. In addition to methane, biodegradation of this high-strength waste also produces sulfide that must be removed in order to prevent costly corrosive impacts on infrastructure. In this work, an anaerobic, phototrophic microbial community enriched from the native population in a swine waste lagoon was evaluated for its potential to remove sulfide from swine waste biogas. Batch experiments with the consortium attained removal efficiencies greater than 97% for sulfide concentrations above 1200 ppm. 16S rRNA gene sequencing revealed that the dominant population was most closely related to the isolate Azospirillum strain C5 (similarity index of 99%). Photomicrograph of the enriched consortium revealed the presence of cells with intracellular globules resembling sulfur storage. The enrichment of Azospirillum-like and the concomitant sulfide consumption suggest that this microorganism played an important role in sulfide removal in the bioreactor.