Mechanized tillage systems effects on properties of a tropical alfisol in watersheds cropped to maize

The effects of 6 years of continuous cultivation in 12 consecutive crops of maize (Zea mays) on changes in the physical and chemical properties of an Alfisol were investigated for two mechanized tillage systems imposed on twin watersheds of about 5 ha each. The tillage methods were no-tillage, with herbicides for weed control, and conventional plowing and harrowing. The soil organic matter content of the 0- to 10-cm layer of the no-tillage watershed increased by 7%, and that of the plowed watershed decreased by 72%. Soil pH declined by 0.3 and 1.7 units in no-tillage and plowed watersheds, respectively. As a consequence of pH changes, exchangeable cations declined with continuous cultivation, regardless of the tillage method, although the rate of decline was more drastic in the plowed than in the no-tillage watershed.Continuous mechanized cultivation substantially decreased infiltration rate. Soil compaction was more severe at the tractor's turning points along the plot's border. The results are discussed in terms of tillage needs and implications for mechanized farming in the tropics.     

Influence of tillage methods and fertilizer application on chemical properties of worm castings in a tropical soil

The effects of four rates of N (0, 40, 80 and 120 kg/ha) and three rates of P (0, 13 and 26 kg/ha) on chemical characteristics of soils and earthworm casts for no-tillage and conventionally disc plowed systems were investigated for a tropical Alfisol. Worm casts contained 2.3 to 1.5 times more organic matter, 1.8 to 1.2 times more nitrogen, 1.6 to 1.3 times more Bray-P, 3.2 to 2.1 times more exchangeable Ca²⁺, 3.8 to 2.5 times more exchangeable Mg²⁺, 3.1 to 2.2 times more exchangeable K⁺, and 1.4 to 1.2 times more exchangeable Na⁺ than the top 10 cm of the soil. The ECEC of worm casts was 3.1 to 2.1 times higher than in the surface soil. The nutrient status of both casts and soil in no-tillage plots was generally superior to that in conventionally plowed treatments. Different rates of N and P application had a significant positive effect on the nutrient status of worm casts. The results are discussed in terms of the role of earthworms in soil productivity.     

Can conservation tillage and residue management enhance energy use efficiency and sustainability of rice-pea system in the Eastern Himalayas?

ABSTRACT

Low productivity and energy use efficiency (EUE) of rice farming are the major concerns for agricultural sustainability in the Eastern Himalayan region of India. A field experiment on rice (Oryza sativa L.)-pea (Pisum sativum L) system was conducted for three consecutive years during 2012–15 in lowland ecosystem to assess the direct and residual impact of tillage and residue management (RM) practises on productivity and sustainability. Significantly higher grain yield of rice was achieved under no-till (NT) than minimum tillage (MT) and conventional tillage (CT). Among RM practises, 50% NPK + green leaf manure, 50% NPK + weed biomass and 50% NPK + in-situ residue retention recorded significantly higher mean grain yields than application of 50% NPK and 100% NPK without residues. Residual effect of MT in preceding rice gave significantly higher green pod yield of succeeding pea than NT and CT. The system EUE was significantly higher under MT (rice)-NT (pea) compared to those of NT-NT and CT-NT systems. The sustainable yield index of rice and pea was maximum under MT-NT followed by NT-NT. Thus, NT/MT with suitable RM practises is a pertinent strategy for sustainable productivity of rice-pea system in the Eastern Himalayas and in similar adjoining regions.     

Soil organic carbon and phosphorus availability regulate abundance of culturable phosphate-solubilizing bacteria in paddy fields

Low availability of phosphorus(P) is a major constraint for optimal crop production, as P is mostly present in its insoluble form in soil. Therefore,phosphate-solubilizing bacteria(PSB) from paddy field soils of the Indo-Gangetic Plain, India were isolated, and their abundance was attempted to be correlated with the physicochemical characteristics of the soils. Ninety-four PSB were isolated on Pikovskaya's agar medium, and quantitative phosphate solubilization was evaluated using NBRIP medium. The isolates solubilized P up to a concentration of 1 006 μg mL~(-1) from tricalcium phosphate with the secretion of organic acids. These isolates were identified by 16 S rRNA gene sequence comparison, and they belonged to Gammaproteobacteria(56 isolates),Firmicutes(28 isolates), Actinobacteria(8 isolates), and Alphaproteobacteria(2 isolates). Phylogenetic analysis confirmed the identification by clustering the isolates in the clade of the respective reference organisms. The correlation analysis between PSB abundance and physicochemical characteristics revealed that the PSB population increased with increasing levels of soil organic carbon, insoluble P, K~+, and Mg~(2+). The promising PSB explored in this study can be further evaluated for their biofertilizer potential in the field and for their use as potent bio-inoculants.     

Voyager 1 explores the termination shock region and the heliosheath beyond

Voyager 1 crossed the termination shock of the supersonic flow of the solar wind on 16 December 2004 at a distance of 94.01 astronomical units from the Sun, becoming the first spacecraft to begin exploring the heliosheath, the outermost layer of the heliosphere. The shock is a steady source of low-energy protons with an energy spectrum approximately E(-1.41 +/- 0.15) from 0.5 to approximately 3.5 megaelectron volts, consistent with a weak termination shock having a solar wind velocity jump ratio r=2.6(-0.2)(+0.4). However, in contradiction to many predictions, the intensity of anomalous cosmic ray (ACR) helium did not peak at the shock, indicating that the ACR source is not in the shock region local to Voyager 1. The intensities of approximately 10-megaelectron volt electrons, ACRs, and galactic cosmic rays have steadily increased since late 2004 as the effects of solar modulation have decreased.     

Managing the soils of sub-saharan Africa

Many constraints to intensive food-crop production in tropical Africa are related to tropical soils. Improved technologies are available for different ecological regions. Important technological innovations include manual land clearing, mulch farming, conservation tillage and tiedridges, agroforestry, cover crops, mixed- and relay-cropping, and early sowing for improved and sustained productivity. Irrigation, animal traction or draft animals, and the use of chemical fertilizers are also important. Much of the agrarian stagnation in Africa is caused by neglect and misuse of the most basic of all resources, the soil. In fact, the root cause of the perpetual famine can be traced to the misuse of soil and water resources and issues related to their misuse. Substantial increases in food production are possible if the proven technologies can be effectively transferred and implemented. Priorities lie in both short-term development projects and in initiating long-term research to understand soil and water resources and how to manage them. The agrarian research must address the issue of improving the welfare of resource-poor farmers.     

Phase chemistry, structure, and radiation effects in lunar samples

Phase chemistry, structure, and radiation effects were studied in rock, breccia, and soil samples. The regolith apparently developed in the final stages of accretion and was modified by later impact processes and radiation weathering. Exposure ages indicate transfer of buried igneous rock fragments to the near surface late in lunar history. With a few exceptions igneous rock fragments, soil, and breccia share the same distinctive chemistry, probably acquired before accretion of the moon. The igneous rocks texturally resemble basaltic achondrites, and the soil and breccias contain glassy spheres analogous to chondrules.     

Energetic charged particles in the magnetosphere of neptune

The Voyager 2 cosmic ray system (CRS) measured significant fluxes of energetic [>/=1 megaelectron volt (MeV)] trapped electrons and protons in the magnetosphere of Neptune. The intensities are maximum near a magnetic L shell of 7, decreasing closer to the planet because of absorption by satellites and rings. In the region of the inner satellites of Neptune, the radiation belts have a complicated structure, which provides some constraints on the magnetic field geometry of the inner magnetosphere. Electron phase-space densities have a positive radial gradient, indicating that they diffuse inward from a source in the outer magnetosphere. Electron spectra from 1 to 5 MeV are generally well represented by power laws with indices near 6, which harden in the region of peak flux to power law indices of 4 to 5. Protons have significantly lower fluxes than electrons throughout the magnetosphere, with large anisotropies due to radial intensity gradients. The radiation belts resemble those of Uranus to the extent allowed by the different locations of the satellites, which limit the flux at each planet.