Organic amendments decomposability influences microbial activity in saline soils

Organic amendments with contrasting biochemical properties were investigated by conducting an incubation experiment in soils irrigated with different levels of saline water. Soil samples were taken from a long-term experimental field plots irrigated with normal water and saline water having electrical conductivity (EC) 6 and 12 dS m^?1, respectively. Finely ground biochar, rice straw (RS), farm yard manure (FYM) and glucose were added at two rates (1% and 2.5% carbon basis) and incubated for 8 weeks at 25°C. Cumulative respiration (CR), microbial biomass carbon and available nutrients (nitrogen and phosphorus) were negatively correlated with EC, irrespective of the source and amount of added carbon (C). Compared with non-saline soil, at EC 12, relative decrease in CR was lowest with glucose (21.0%) followed by RS (32.0%), FYM (46.0%) and biochar (55.0%). Dissolved organic carbon was positively correlated with salinity and its concentration was higher in treatments with higher rate of C addition (2.5% C). This study showed decomposability of organic amendments and their rate of addition determines microbial activity in saline soils. Further, lower nitrogen (N) release from amendments under saline conditions limits microbial ability to utilize available C for satisfying their energy needs.     

Effect of green manuring (Sesbania aculeata) on zinc equilibria in submerged calcareous and non-calcareous soils

Summary A pot experiment was conducted to study the effect of green manuring (Sesbania aculeata) on pH, electrical conductivity (EC), Zn concentration and ZN equilibria in a calcareous and a non-calcareous soil under submerged conditions. The soil solutions were drawn anaerobically by gravity and analysed for pH, EC and Zn. Green manuring lowered the pH and increased the EC throughout submergence compared with the untreated control. The effect of green manuring was more pronounced in non-calcareous soil. The concentration of water-soluble Zn under submergence alone continued to decline up to the end of the experiment in both soils. But Zn concentration in green manure-amended soil was lower during the initial stages and higher in the later stages in comparison with the unamended soil. Zn potential values in the case of submergence alone were within the range of the ZnCo₃-Zn²⁺ (aq) system up to 1 week and 4 weeks for non-calcareous and calcareous soil, respectively. Thereafter they shifted to those of the Zn-soil (unknown solid phases)-Zn²⁺ (aq) system. Under green manuring the values were within the range of the latter system throughout the experiment.     

Straw management and tillage effects on soil water storage under field conditions

Abstract. A two year field study was conducted to evaluate the effects of straw management and tillage on the soil profile (1.5m) water storage, nature of the moisture profile, infiltration and sorptivity as influenced by rainfall, evaporativity (E₀) and soil texture. The straw mulch treatment stored more moisture under low E₀ rainy conditions in three coarse to medium textured soils. Straw incorporation treatment was better under low E₀ rain free conditions, as well as under high E₀ rainy conditions in the two coarser textured soils. In the coarsest textured soil, tillage and straw mulching were not effective in maintaining greater soil water storage under high E₀ because of the very open nature of the soil. The soil moisture profiles showed a sharper increase in water content below the tilled layer in the tillage and straw- incorporation treatments than the untreated and straw mulch treatments. Tillage and straw incorporation treatments increased the sorptivity of the soil compared with untreated and straw mulch treatments respectively. The results of this study suggest that when selecting a suitable soil water conservation practice to increase water storage in the soil profile, information on soil texture and weather (rain and evaporativity) must be considered.     

Multilocation evaluation and selection of stable genotypes for reaction to downy mildew in pearl millet

Twenty-five pearl millet (Pennisetum typhoides (Burm. f.) Stapf and Hub. = P. americanum (L.) K. Schum.) genotypes were evaluated for resistance to downy mildew (Sclerospora graminicola (Sacc.) Schroet.) at 10 different locations in India and Africa during 1979 and 1980. The objective of this work was to identify genotypes with stable and generalized resistance. Genotypic differences in linear regression coefficients were found and regression lines for downy mildew incidence in the various genotypes tended to converge. It was concluded from this that selection on the basis of disease severity would enable genotypes that are superior at all disease levels to be selected. Seven genotypes, namely 700516, 700651, J-1486 × 700787-2-10, P-7, EB-83-2, NC-7174 and SSC-7218, showed low disease scores, average regressions and non-significant deviations, and therefore expressed stable, generalized resistance. Genotype 700251 was particularly suitable for high-disease environments. BJ-104, an important Indian hybrid cultivar, was very unstable and susceptible to downy mildew.     

Progeny mean, heterosis and heterobeltiosis inSolanum tuberosum x tuberosum andS. tuberosum x andigena families under a short day sub-tropic environment

Summary Solanum tuberosum x tuberosum (TxT) families were compared withS. tuberosum x andigena (TxA) families as progeny mean, heterosis and heterobeltiosis for ten important agronomic characters by evaluating 72 cross combinations (36 of TxT and 36 of TxA, from 18 common female parents), for three successive seedling and clonal generations under short day sub-tropic conditions. TxA families had more vigorous progenies, higher tuber yield, higher number of tubers, larger tubers and better general impression than TxT families. The TxA families were inferior to the TxT families for characters such as tuber colour and uniformity of tuber colour, but their progeny means were within the acceptable range. High progeny means of TxA families were associated with high heterosis and high heterobeltiosis in these families, although there were a few exceptions. High mean performance for tuber yield and tuber number were associated with high variance of these traits in TxA families. It is concluded that, unlike under long day environments, andigena adapted to short days can be used advantageously for exploiting heterosis in the potato breeding programmes of short day subtropic environments.     

Aerial Application of Insecticides for the Control of the Mango-Hopper

Abstract

Aerial application of malathion LVC at 893 and 1330 g/ha, malathion EC at 927 g/ha, carbaryl SP at 557, 841 and 1113 g/ha, and endosulfan ec at 432 and 649 g/ha was tested for the control of mango-hopper at 8 places in Hoshiarpur and Ropar districts of the Punjab using a fixed-wing aircraft for spraying in the end of February. The penetration of spray material through the deep canopy of seedling mango trees was good. There was 86–100% reduction in the pest population over control 9 days after treatment. Malathion LVC at 1330 g/ha proved to be the best. It gave an excellent knock-down and did not register any significant build-up in the mango-hopper population up to 51 days after spraying.     

Trace metal leaching in a spodosol irrigated with tomato packinghouse wastewater

Tomato packinghouse wastewater is often applied to land in Florida, but the sandy soils, low levels of organic matter, shallow groundwater and abundant rainfall present favourable conditions for leaching of wastewater‐borne trace metals. We investigated the leaching of copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) from a sandy siliceous, hyperthermic Oxyaquic Alorthods packed in two distinct soil horizons (Ap and A/E) in 12 polyvinyl chloride soil columns (30 cm internal diameter × 50 cm length). Thirty leaching events were conducted by daily applying tomato packinghouse wastewater at low (0.84 cm/day), medium (1.68 cm/day) and high (2.51 cm/day) rates for 30‐days period. Control treatment received de‐ionized water at the same application rate as the medium treatment (1.68 cm/day). Application of wastewater at three rates did not affect the mean concentrations of Cu in leachate (0.19–0.2 mg/L) because of retention of Cu in the soil profile. However, leachate Zn concentrations were twice as much (0.3–0.32 mg/L) following wastewater application than for the control (0.13 mg/L) treatment. Leaching losses of Cu and Zn were smaller with the medium wastewater treatment (similar to control treatment) than for the high wastewater treatment. Concentrations of Cu and Zn at the 50 cm soil depth were much less than the drinking water standards, suggesting a minimum risk of groundwater contamination under fields to which wastewater was applied. Our results imply that tomato packinghouse wastewater can be safely land‐applied at 1.68 cm/day to Florida’s Spodosols under vegetable production without concerns of significant trace metal leaching.     

Peroxidase Isozyme Pattern in Pearl Millet Lines Resistant and Susceptible to Downy Mildew

Peroxidase isozyme patterns of five downy mildew (DM) resistant inbred lines (PIB-57-1, PIB-1248, PIB-1356, PIB-1364 and PIB-1440), five susceptible lines (PIB-1335-1-1, PIB-1314-2-2, PIB-2231-1, 7042 and PIB-1530-1-1) and DM free plants from the susceptible lines of pearl millet were studied. The results suggested a possible involvement of an isoperoxidase (C9) in imparting the resistance. The involvement of two other isozymes (C5 and C6) was also indicated in the1 resistance mechanism. The specific differentiation m particular isozyme pattern can be a useful criterion for characterization of resistance to downy mildew.     

Soil texture, climate and management effects on plant growth, grain yield and water use by rainfed maize–wheat cropping system: Field and simulation study

In sub-mountain tract of Punjab state of India, maize (Zea mays, L.) and wheat (Triticum aestivum L.) crops are grown as rainfed having low crop and water productivity. To enhance that, proper understanding of the factors (soil type, climate, management practices and their interactions) affecting it is a pre-requisite. The present study aims to assess the effects of tillage, date of sowing, and irrigation practices on the rainfed maize–wheat cropping system involving combined approach of field study and simulation. Field experiments comprising 18 treatments (three dates of sowing as main, three tillage systems as subplot and two irrigation regimes as the sub-subplot) were conducted for two years (2004–2006) and simulations were made for 15 years using CropSyst model. Field and simulated results showed that grain yields of maize and wheat crops were more in early July planted maize and early November planted wheat on silt loam soil. Different statistical parameters (root mean square error, coefficient of residual mass, model efficiency, coefficient of correlation and paired t-test) indicated that CropSyst model did fair job to simulate biomass production and grain yield for maize–wheat cropping system under varying soil texture, date of planting and irrigation regimes.     

Effects of sowing date, tillage and residue management on productivity of cotton (Gossypium hirsutum L.)–wheat (Triticum aestivum L.) system in northwest India

In southwestern region of Punjab in north India, sowing dates of cotton crop in cotton (Gossypium hirsutum L.)–wheat (Triticum aestivum L.) system are staggered from last week of April to mid of May depending upon the surface water supply from canal as ground water is not fit for irrigation. Further, farmers practice intensive cultivation for seedbed preparation and burning of wheat straw before sowing of cotton crop. With the present farmers’ practices, yields have become static and system has become non-profitable. Field experiments were conducted on Entisols for two rotations of cotton–wheat system during the years of 2004–2005 and 2005–2006 in split plot design to study the direct and interactive effects of date of sowing and tillage-plus-wheat residue management practices on growth and yield of cotton and wheat and to increase the profitability by reducing the tillage operations, which costs about 50% of the sowing cost. The pooled analysis showed that in cotton crop, there was a significant interaction between year × dates of sowing. Among different tillage-plus-wheat residue management practices yields were 23–39% higher in tillage treatments than minimum-tillage. In wheat, grain yield in tillage treatments were at par. Water productivity amongst the tillage treatments in cotton was 19–27% less in minimum tillage than others tillage treatments. Similar trend was found in wheat crop. Remunerability of the cotton–wheat system was more with a combination of reduced tillage in cotton and minimum tillage in wheat than conventional tillage.