Impact of Eucalyptus biochar application to upland rice-sugarcane cropping systems on enzyme activities and nitrous oxide emissions of soil at sugarcane harvest under incubation experiment

This research studied the effect of biochar addition before upland rice planting, followed by sugarcane cropping, on soil fertility (nitrogen mineralization, β-glucosidase and urease activities), and mitigating greenhouse gases emission at sugarcane harvest. An incubation experiment was designed utilizing soil samples taken from a sugarcane field at final harvest with treatments, (i) Control, with no biochar or fertilizer application to upland rice (ii) CF, with fertilizer application at recommended rates; (iii) BC1, with biochar addition at the rate of 3.125?Mg ha^?1 + CF; (iv) BC2, with biochar addition at the rate of 6.25?Mg ha^?1 + CF. Results showed that, at the last sampling dates, soil enzyme activities of the biochar treatments were significantly greater than those of the control treatment. The lowest cumulative carbon dioxide and nitrous oxide emission was observed in the BC2 treatment. Thus, the BC2 treatment could increase both soil fertility and mitigate global warming.     

Novel phlebovirus-like-AYUT and Stenotrophomonas maltophilia bacterial co-infection in a Rhipicephalus sanguineus s.l. tick

Veterinary Research Communications - Tick-borne viruses and bacteria that can cause diseases of animals and humans have high impact and are of concern as significant threats to human health...     

Mixing groundnut residues and rice straw to improve rice yield and N use efficiency

Groundnut as a pre-rice crop is usually harvested 1–2 months before rice transplanting. During this lag phase much of N in groundnut residues could be lost due to rapid N mineralization. Mixing of abundantly available rice straw with groundnut residues may be a means for reducing N and improve subsequent crop yields. The objectives of this experiment were to investigate the effect of mixing groundnut residues and rice straw in different proportions on (a) growth and yield of succeeding rice, (b) groundnut residue N use efficiency and (c) N lost (¹⁵N balance) from the plant–soil system and fate of residue N in soil fractions. The experiment consisted of six treatments: (i) control (no residues), (ii) NPK (at recommended rate, 38 kg N ha⁻¹), (iii) groundnut residues 5 Mg ha⁻¹ (120 kg N ha⁻¹), (iv) rice straw 5 Mg ha⁻¹ (25 kg N ha⁻¹), (v) 1:0.5 mixed (groundnut residues 5 Mg: rice straw 2.5 Mg ha⁻¹), and (vi) 1:1 mixed (groundnut residues 5 Mg: rice straw 5 Mg ha⁻¹). After rice transplanting, samples of the lowland rice cultivar KDML 105 were periodically collected to determine growth and nutrient uptake. At final harvest, dry weight, nutrient contents and ¹⁵N recovery of labeled groundnut residues were evaluated.     

Eucalyptus biochar application enhances Ca uptake of upland rice,soil available P,exchangeable K,yield, and N use efficiency of sugarcane in a crop rotation system

It was hypothesized that the application of eucalyptus biochar enhances nutrient use efficiencies of simultaneously supplied fertilizer, as well as provides additional nutrients (i.e., Ca, P, and K), to support crop performance and residual effects on subsequent crops in a degraded sandy soil. To test this hypothesis, we conducted an on‐farm field experiment in the Khon Kaen province of Northeastern Thailand to assess the effects of different application rates of eucalyptus biochar in combination with mineral fertilizers to upland rice and a succeeding crop of sugarcane on a sandy soil. The field experiment consisted of three treatments: (1) no biochar; (2) 3.1 Mg ha^?1 biochar (10.4 kg N ha^?1, 3.1 kg P ha^?1, 11.0 kg K ha^?1, and 17.7 kg Ca ha^?1); (3) 6.2 Mg ha^?1 biochar (20.8 kg N ha^?1, 6.2 kg P ha^?1, 22.0 kg K ha^?1, and 35.4 kg Ca ha^?1). All treatments received the same recommended fertilizer rate (32 kg N ha^?1, 14 kg P ha^?1, and 16 kg K ha^?1 for upland rice; 119 kg N ha^?1, 21 kg P ha^?1, and 39 kg K ha^?1 for sugarcane). At crop harvests, yield and nutrient contents and nitrogen (N) use efficiency were determined, and soil chemical properties and pH₀ monitored. The eucalyptus biochar material increased soil Ca availability (117 ± 28 and 116 ± 7 mg kg^?1 with 3.1 and 6.2 Mg ha^?1 biochar application, respectively) compared to 71 ± 13 mg kg^?1 without biochar application, thus promoting Ca uptake and total plant biomass in upland rice. Moreover, the higher rate of eucalyptus biochar improved CEC, organic matter, available P, and exchangeable K at succeeding sugarcane harvest. Additionally, 6.2 Mg ha^?1 biochar significantly increased sugarcane yield (41%) and N uptake (70%), thus enhancing N use efficiency (118%) by higher P (96%) and K (128%) uptake, although the sugar content was not increased. Hence, the application rate of 6.2 Mg ha^?1 eucalyptus biochar could become a potential practice to enhance not only the nutrient status of crops and soils, but also crop productivity within an upland rice–sugarcane rotation system established on tropical low fertility sandy soils.     

Soil fungal communities and enzyme activities in a sandy, highly weathered tropical soil treated with biochemically contrasting organic inputs

The regulative effect of long-term application of biochemically contrasting organic inputs such as rice straw (4.7 g?N; 6.5 g polyphenols), groundnut stover (22.8 g?N; 12.9 g polyphenols) and leaf litter of tamarind (13.6 g?N; 31.5 g polyphenols) and dipterocarp (5.7 g?N; 64.9 g polyphenols) on fungal decomposers was studied in a tropical sandy soil. Fungal decomposers were assayed by 18S rRNA gene-based community profiling and were combined with measurements of selected enzyme activities. Dipterocarp residue application depressed fungal abundance, but promoted specialized decomposers (e.g., Aspergillus fumigatus and Anguillospora longissima) with increases in polyphenol oxidase activity. The degree of functional redundancy for invertase and B-glucosidase activities was induced after the addition of easily decomposable rice straw and groundnut stover. Higher N availability in the tamarind treatment increased, in contrast to low N rice straw, fungal abundance (i.e., Fusarium oxysporum, Myceliopthora thermophila, and Aspergillus versicolor) and promoted invertase and B-glucosidase activities, while peroxidase activity was depressed. In addition, N availability seemed to regulate not only decomposing soil fungi, but also the abundance of protozoan decomposers whose actual contribution to N turnover in soils is still poorly understood. Prospective research should thus consider apart from studying decomposing fungi also protozoa and bacteria to better understand the microbially mediated degradation of complex organic materials in soils.     

Regulating mineral N release and greenhouse gas emissions by mixing groundnut residues and rice straw under field conditions

Groundnut as a pre‐rice crop is usually harvested 1–2 months before rice transplanting, during which much of legume residue N released could be lost. Our objectives were to investigate the effect of mixing groundnut residues (GN, 5 Mg ha^?1) with rice straw (RS) in different proportions on: (i) regulating N dynamics, (ii) potential microbial interactions during decomposition, and (iii) associated nitrous oxide and methane emissions at weekly intervals during the lag phase until rice transplanting (i, ii) or harvest (iii). Decomposition was fastest in groundnut residues (64% N lost) with a negative interaction for N loss when mixed 1:1 with rice straw. Adding groundnut residues increased mineral N initially, while added rice straw led to initial microbial N immobilization. Mineral N in mixed residue treatments was significantly greatest at the beginning of rice transplanting. Soil microbial N and apparent efficiency were higher, while absolute and relative microbial C were often lowest in groundnut and mixed treatments. Microbial C:N ratio increased with increasing proportion of added rice straw. N₂O losses were largest in the groundnut treatment (12.2 mg N₂O‐N m^?2 day^?1) in the first week after residue incorporation and reduced by adding rice straw. N₂O‐N emissions till rice harvest amounted to 0.73 g N₂O‐N m^?2 in the groundnut treatment. CH₄ emissions were largest in mixed treatments (e.g. 155.9 g CH₄ m^?2, 1:1 treatment). Mixing residues resulted in a significant interaction in that observed gaseous losses were greater than predicted from a purely additive effect. It appears possible to regulate N dynamics by mixing rice straw with groundnut residues; however, at a trade‐off of increased CH₄ emissions.