Tillage and drainage impact on soil quality: II. Tensile strength of aggregates, moisture retention and water infiltration

Tillage-induced changes in soil quality are important to understanding soil strength and water retention and transmission properties. Thus, this study was conducted to assess the effects of two tillage systems under un-drained and drained conditions on tensile strength (TS) of 5–8 mm aggregates, soil water characteristics (SWC), plant available water (PAW), and the water infiltration rate (i). Soil properties were determined mainly in the surface (0–10 cm) layer on a Crosby (fine, mixed, mesic, Aeric Ochraqualf) silt loam soil at the Waterman Farm of the Ohio State University, Columbus, OH on a 14-year-old field study. Effect of two tillage treatments comprising no-tillage (NT) and conventional tillage (CT) were studied for two levels of drainage: un-drained (UD) and tile drained (D). The TS for 0–10 cm depth was significantly (P ≤ 0.01) affected by tillage and drainage treatments, and was higher in CT than NT by 61% in UD and by 48% in D soil. In comparison, TS increased by 13% in NT and 4% in CT in D compared with the UD treatments. Soil organic carbon (SOC) in 0–10 cm depth of NT–UD treatment was 23% higher than CT–UD treatment and 38% more than NT–D treatments. Tillage and drainage impact on SWC was non-significant at 0 kPa suction, but significant (P ≤ 0.1) at −3, −6, −10, −30, −100 and −300 kPa suctions indicating that water was retained more in NT–UD than CT–UD soil. The PAW was significantly influenced by drainage (P ≤ 0.01) but not by tillage treatments. Yet, there existed a general trend of about 8% more PAW in NT–UD than CT–UD treatments. In contrast, PAW was 48% more in soil from NT–UD than NT–D treatments. PAW increased with increase in the SOC concentration (R² = 0.89; P ≤ 0.01). There were also differences in soil water sorptivity (S), and equilibrium infiltration rate (i_c) in NT–UD compared with CT–UD treatments. A positive and significant correlation (r = 0.57, P ≤ 0.05) occurred between i_c and SOC concentration. The value of S was more in NT–UD by 70% than CT–UD, and 46% in NT–D than CT–D. Similarly, the i_c was more in NT than CT by 119% in UD compared with 82% in D soil. The value of A in NT was higher than that in CT by 39% and 12% in UD and D treatments, respectively. The mean cumulative infiltration (I) in 3 h was 71.4 cm in NT versus 44.0 cm in CT in UD compared with 62.1 cm in NT and 48.4 cm in CT for the D treatment. The I was positively and significantly correlated with SOC concentration (r = 0.32, n = 12, P ≤ 0.1) indicating improvement of I with increase in SOC concentration. Results of this study suggest that conversion from CT to NT management system may reduce the risk of surface runoff, increase soil aggregation, and improve soil hydrological properties.     

Population genetic structure of <Emphasis Type="Italic">Rhizoctonia solani</Emphasis> AG1IA from rice field in North India

Rhizoctonia solani AG1IA is an important fungal pathogen causing significant yield and quality losses in rice production. However, little is known about the levels of genetic diversity and structure of this pathogen in North India. Out of 240 samples collected from different rice-growing regions of North India, 112 isolates were identified as R. solani AG1IA subgroups using species-specific primers. All 112 isolates were organized into four groups on the basis of percent disease index (PDI). The majority of the isolates were weakly virulent. Population genetic analysis was performed within and between populations using inter simple sequence repeat (ISSR) markers. A total of 8249 alleles were identified from the 112 isolates of R. solani AG1IA through analysis of the ten inter simple sequence repeat markers. All the ten ISSR markers were polymorphic. The average number of bands per primer was 7.3 which ranged in size from 250 to 1500 bp. Genetic structure of the isolates using inter simple sequence repeat primers showed high degree of polymorphism (PIC ≥0.81). The analysis of molecular variance (AMOVA) indicated that most of the genetic diversity occurred within populations (60%), while the variability among populations and among regions contributed 25 and 15%, respectively. Overall, the present study reveals that a large variation exists among rice-infecting isolates of R. solani AG1IA in North India. Fingerprinting of the isolates using ISSRs along with phenotypic characterization and virulence analysis will help epidemiological studies that can provide new insights into pathogen biology and disease spread.     

Conservation tillage and mulching effects on the adaptive capacity of direct-seeded upland rice (Oryza sativa L.) to alleviate weed and moisture stresses in the North Eastern Himalayan Region of India

A field experiment was conducted to study the effects of tillage and mulch on weed growth, soil moisture storage, productivity and profitability of upland rice during 2012–2013 at Lembucherra, India. Tillage treatments included CT-RI: conventional tillage with 100% residue incorporation and NT-RR: no-till with 100% residue retention. Mulches included rice straw (SM), Gliricidia (GM), brown manuring (BM) and none (NM). CT-RI registered the highest total weed density (89–168 weeds m^?2) and biomass (9.6–183 g dry weight m^?2) than those for the NT-RR (75–161 weed m^?2 and 8–155 g dry weight m^?2). In addition, NT-RR stored (122–172 mm) more soil moisture (0–40 cm soil depth) in comparison with that for the CT-RI treatment (110–161 mm) during crop growing season. Tillage treatments did not have the significant effect on yields. NT-RR reduced the cost of cultivation by 31.5% compared with that for the CT-RI. Thus, the net returns under NT-RR were more than those for the CT-RI. The BM recorded the lowest weed biomass and density as compared to that under other mulches. Therefore, cultivation of upland rice using NT along with BM mulching enhanced productivity and profitability of rice cultivation in India.     

Mapping of easy to screen SSR markers for selection of RFLP markers-bracketed downy mildew resistance QTLs in pearl millet

There is a growing necessity to replace chemical agents with ecofriendly materials, arising from the impact on the environment and/or human health, which calls for the design of new broad-spectrum fungicides. In this work, chitosan oligomers (COs), propolis (Ps) and silver nanoparticles (AgNPs) mixtures in solution were assessed to control the growth of different phytopathogenic fungi and oomycetes in vitro. Binary solutions of COs-Ps and COs-AgNPs evinced the highest antifungal effect against Fusarium circinatum and Diplodia pinea fungi, respectively, with a ca. 80% reduction in their mycelial growth. The COs solution by itself also proved to be greatly effective against Gremmeniella abietina, Cryphonectria parasitica and Heterobasidion annosum fungi, causing a reduction of 78%, 86% and 93% in their growth rate, respectively. Likewise, COs also attained a 100% growth inhibition on the oomycete Phytophthora cambivora. On the other hand, Ps inhibited totally the growth of Phytophthora ×alni and Phytophthora plurivora. The application of AgNPs reduced the mycelial growth of F. circinatum and D. pinea. However, the AgNPs in some binary and ternary mixtures had a counter-productive effect on the anti-fungal/oomycete activity. In spite of the fact that the anti-fungal/oomycete activity of the different treatments showed a dependence on the particular type of microorganism, these solutions based on natural compounds can be deemed as a promising tool for control of tree diseases.     

Influence of continuous application of inorganic nutrients to a Maize–Wheat rotation on soil enzyme activity and grain quality in a rainfed Indian soil

To explore long-term impact of organic and inorganic fertilizers on soil health and grain quality, we monitored the enzyme activities and chemical properties of soil; and chemical composition of grain from eight treatments at an experimental field site established in 1996. There were eight treatments applied to both wheat and maize seasons: a control; four inorganic fertilizers, that is, nitrogen and phosphorus (NP), nitrogen and potassium (NK), phosphorous and potassium (PK) and nitrogen, phosphorus and potassium (NPK); farm yard manure alone (FYM) and addition of FYM at two different doses (100 and 50% of recommendation) to NPK that is, NPK + FYM and ½ NPK + FYM. After 11 years of the experiment the NPK + FYM and ½ NPK + FYM treatments had the highest yields, about 5 Mg maize ha⁻¹ and 2 Mg wheat ha⁻¹ with about 2 and 0.5 Mg ha⁻¹, respectively more than the NPK treatments. The dehydrogeanse activity of soils increased significantly in FYM and ½ NPK + FYM. Except urease all other enzymatic activities were increased in those treatments, which received manure. Urease activity was higher in mineral-N applied plots. Grain protein content of both maize and wheat was highest in mineral fertilized plots. Test weight also increased significantly on application of mineral fertilizer. Plots treated with half dose of recommended mineral fertilizer along with FYM were higher in urease, phosphomono and diesterase activities than that of NPK + FYM treated plots. Long-term application of inorganic nutrients along with FYM improved grain mineral composition and yield. Inhibition of few enzymatic activities were also observed upon application of inorganic nutrients either alone or in combination.     

Long-Term Effects of Different Passages of Vehicular Traffic on Soil Properties and Carbon Storage of a Crosby Silt Loam in USA

The passage of vehicles with heavy axle loads causes soil compaction, and this adversely affects soil properties and crop yield.The adverse effects can persist for several years due to significant changes in key soil properties. However, the mechanisms of the aforementioned effects are not well understood for conservation agriculture(CA)(e.g., no-till(NT)) wherein the use of heavy machinery is considerably common. Therefore, known compaction forces(0 Mg load for compaction(NT-0, control), two passages of 2.5 Mg water wagon axle load(NT-2), and four passages of 2.5 Mg water wagon axle load(NT-4)) were applied to all the plots annually for 20 consecutive years. The experiment was established in 1997 at the Waterman Agricultural and Natural Resources Laboratory(WANRL), Ohio State University, Columbus, Ohio. Each treatment was replicated thrice. Soil samples were obtained in November2016 to determine the effects of variations in the axle load and vehicular passages on carbon(C) and nitrogen(N) storage and selected soil properties of a Crosby silt loam soil under NT-based corn-soybean rotation with residue retention in Central Ohio, USA. Three locations were also randomly selected in an adjoining natural woodlot(WL) soil plot and sampled(30 m away from the compaction field) to compare the effects of vehicular traffic on soil under NT with WL soil. Results revealed that soil bulk density(ρb) and total porosity at 0–10 and 10–20 cm depths were not affected by the passages of vehicular traffic for 20 years under the NT system.The penetration resistance(PR)(1.86 and 2.03 MPa at 0–10 and 10–20 cm soil depths, respectively) was significantly higher under NT-4 compared with that under other treatments. Saturated hydraulic conductivity at 0–10 and 10–20 cm soil depths ranged from19.7 to 31.4 and 18.5 to 29.5 mm d~(-1), respectively, across all the treatments. The proportion of macroaggregates( 0.25 mm) and microaggregates( 0.25 mm), mean weight diameter and geometric mean diameter of aggregates, pH, electrical conductivity, and C and N contents and storage did not differ significantly between the treatments at either of the sampling soil depths. The data indicated that 2 to 4 passages of vehicles with 2.5 Mg of axle load did not cause significant compaction of the Crosby silt loam under NT compared with that under natural WL. Therefore, the continuous cultivation of row crops with NT and residue retention is feasible with passages of vehicular traffic for well-drained soils in Central Ohio.     

The ability of indigenous micro-organisms to degrade isoproturon, atrazine and mecoprop within aerobic UK aquifer systems

The potential for the herbicides isoproturon, atrazine and mecoprop to degrade in the major UK aquifers of chalk, sandstone and limestone was studied using laboratory microcosms spiked at 100 microg litre(-1). Significant mecoprop degradation was only observed in sandstone groundwater samples. Atrazine transformation, based on the formation of metabolites, did occur in most groundwater samples, but only at a rate of 1-3% per year. A potential to degrade isoproturon was observed in groundwater samples from each of the aquifer types, with the most rapid and consistent degradation occurring at the sandstone field site. Biodegradation was confirmed by the formation of monodesmethyl- and didesmethyl-isoproturon. Isoproturon degradation potential rates obtained from the groundwater microcosms could not be correlated with either dissolved organic carbon or numbers of bacteria in the groundwater. It was noted that the ability of the groundwater at a field site to degrade a pesticide was not related to performance of the soil above.     

Cryptosporidium meleagridis in an Indian ring-necked parrot (Psittacula krameri)

OBJECTIVE: To perform a morphological and genetic characterisation of a Cryptosporidium infection in an Indian ring-necked parrot (Psittacula krameri) and to compare this with C meleagridis from a turkey. DESIGN: Tissue and intestinal sections from an Indian ring-necked parrot were examined microscopically for Cryptosporidium. The organism was also purified from the crop and intestine, the DNA extracted and a portion of the 18S rDNA gene amplified, sequenced and compared with sequence and biological information obtained for C meleagridis from a turkey as well as sequence information for other species of Cryptosporidium. RESULTS: Morphological examination of tissue sections from an Indian ring-necked parrot revealed large numbers of Cryptosporidium oocysts attached to the apical border of enterocytes lining the intestinal tract. Purified Cryptosporidium oocysts measured about 5.1 x 4.5 microns, which conformed morphologically to C meleagridis. The sequence obtained from this isolate was identical to sequence information obtained from a C meleagridis isolate from a turkey. CONCLUSION: Cryptosporidium meleagridis was detected in an Indian ring-necked parrot using morphological and molecular methods. This is the first time that this species of Cryptosporidium has been reported in a non-galliform host and extends the known host range of C meleagridis.