Short Response of Spring Wheat to Tillage,Residue Management and Split Nitrogen Application in a Rice-Wheat System

A field experiment was conducted to study the impact of tillage, crop residue management and nitrogen (N) splitting on spring wheat (Triticum aestivum L.) yield over 2 yr (2010-2012) in a rice (Oryza sativa L.)-wheat system in northwestern Pakistan. The experiment was conducted as split plot arranged in randomized complete blocks design with three replications. Treatments comprised six tillage and residue managements: zero tillage straw retained (ZTsr), zero tillage straw burnt (ZTsb), reduced tillage straw incorporated (RTsi), reduced tillage straw burnt (RTsb), conventional tillage straw incorporated (CTsi), and conventional tillage straw burnt (CTsb) as main plots and N (200 kg ha⁻¹) was applied as split form viz., control (no nitrogen & no splitting, N₀S₀); 2 splits of total N, half at sowing and half at the 1st irrigation (i.e., 20 d after sowing (DAS)) (NS₁); 3 splits of total N, 1/3 at sowing, 1/3 at the 1st irrigation, and 1/3 at the 2nd irrigation (NS₂); 4 splits of total N, 1/4 at sowing, 1/4 at the 1st irrigation, 1/4 at the 2nd irrigation (45 DAS), and 1/4 at the 3rd irrigation (70 DAS) (NS₃); and 4 splits of total N, 1/4 at the 1st irrigation, 1/4 at the 2nd irrigation, 1/4 at the 3rd irrigation, and 1/4 at the 4th irrigation (95DAS) (NS₄) as sub plots. The results showed that the most pikes m⁻², grains/spike, 1000-grain weight, grain yield, and N use efficiency (NUE) were obtained at zero tillage, straw retained and 4 splits application of total N (i.e., at sowing 20, 45 and 70 d after sowing). The results indicated that ZTsr with application of 200 kg N ha⁻¹ in 4 equal splits viz. at sowing 20, 45 and 70 d after sowing is an appropriate strategy that enhanced wheat yield (7436-7634 kg ha⁻¹) and N efficiency (28.6-29.5 kg kg⁻¹) in rice-wheat system.     

Farmers' knowledge and perceptions of the stunting disease of Napier grass in Western Kenya

Production of Napier grass, Pennisetum purpureum, the most important livestock fodder in Western Kenya, is severely constrained by Napier stunt (Ns) disease. Understanding farmers' knowledge, perceptions and practices is a prerequisite to establishing an effective disease management approach. Using a random sample of 150 farmers drawn from Bungoma, Busia and Teso districts of Western Kenya, this study sought to: (i) assess farmers' perceptions and knowledge of Ns disease, including its effects on the smallholder dairy industry; (ii) record farmers' current practices in managing Ns disease; and (iii) identify Ns disease management challenges and intervention opportunities in order to develop an efficient integrated disease management approach. The majority (86·7%) of the farmers were aware of Ns disease and observed that it was spreading rapidly in the region, which was perfectly predicted by farmers' access to agricultural information (marginal effect = 0·164), indicating a need for extension platforms for knowledge sharing among the industry stakeholders. The disease had affected Napier grass yields so most farmers could not feed their livestock on the amounts they produced, and they were buying Napier grass. Those who relied on income from selling Napier grass received less due to loss in productivity. Milk production had reduced by over 35%. The cause of the disease was unknown to the farmers, with no effective disease management strategy available to them. An integrated disease management approach needs to be developed to fit within the mixed farming systems, supported by simple decision aids.     

Population dynamics of citrus leaf miner on different varieties of citrus in correlation with abiotic environmental factors in Sargodha District,Punjab, Pakistan

From January 2010 to December 2011, samples of leaves from citrus varieties Kinnow, Musambi and Feutral were taken from the five tehsils (administrative subdivisions) of Sargodha District in Pakistan including Sargodha, Bahalwal, Silanwalli, Sahiwal and Kotmomin, to study the population trends in citrus leaf miner (CLM), Phyllocnistis citrella (Stainton) (Lepidoptera: Gracillariidae), and its correlation with various environmental factors: (temperature, humidity and rainfall); plant morphological factors: moisture contents of leaves, leaf thickness, surface area (cm ² ), and biochemical percentage of calcium, potassium and magnesium in leaves. The maximum population of CLM was observed on Kinnow and Feutral, followed by Musambi. The effect of these factors on the larval population was 8.39- 2.30(Mg)+2.73(K)-0.398(Ca)-0.100(Temp)0.038(Humidity)+0.567(Rain)+0.07(Moist) 1.01 (Thickness)-0.022(Surface area). This equation revealed that magnesium, calcium, temperature, humidity, leaf thickness and leaf surface area are negatively correlated with larvae population, whereas potassium, rainfall and moisture are positively correlated with larvae population.     

Consequences of narrow crop row spacing and delayed Echinochloa colona and Trianthema portulacastrum emergence for weed growth and crop yield loss in maize

Echinochloa colona and Trianthema portulacastrum are weeds of maize that cause significant yield losses in the Indo‐Gangetic Plains. Field experiments were conducted in 2009 and 2010 to determine the influence of row spacing (15, 25 and 35 cm) and emergence time of E. colona and T. portulacastrum (0, 15, 25, 35, 45 and 55 days after maize emergence; DAME) on weed growth and productivity of maize. A season‐long weed‐free treatment and a weedy control were also used to estimate maize yield and weed seed production. Crop row spacing as well as weed emergence time had a significant influence on plant height, shoot biomass and seed production of both weed species and grain yield of maize in both years. Delay in emergence of weeds resulted in less plant height, shoot biomass and seed production. However, increase in productivity of maize was observed by delay in weed emergence. Likewise, growth of both weed species was less in narrow row spacing (15 cm) of maize, as compared with wider rows (25 and 35 cm). Maximum seed production of both weeds was observed in weedy control plots, where there was no competition with maize crop and weeds were in rows 35 cm apart. Nevertheless, maximum plant height, shoot biomass and seed production of both weed species were observed in 35 cm rows, when weeds emerged simultaneously with maize. Both weed species produced only 3–5 seeds per plant, when they were emerged at 55 DAME in crop rows spaced at 15 cm. Infestation of both weeds at every stage of crop led to significant crop yield loss in maize. Our results suggested that narrow row spacing and delay in weed emergence led to reduced weed growth and seed production and enhanced maize grain yield and therefore could be significant constituents of integrated weed management strategies in maize.     

Dietary L‐tryptophan requirement of fingerling stinging catfish,Heteropneustes fossilis (Bloch)

To quantify dietary L‐tryptophan requirement of fingerling Heteropneustes fossilis (6.66 ± 0.08 g), casein–gelatin‐based isonitrogenous (38% CP) and isoenergetic (14.72 kJ g^?1 DE) purified diets with eight levels of L‐tryptophan (0.12%, 0.16%, 0.20%, 0.24%, 0.28%, 0.32%, 0.36%, 0.40% dry diet) were fed to triplicate groups of fish twice daily to apparent satiation for 12 weeks. Incremental levels of dietary tryptophan from 0.12 to 0.28% significantly (P < 0.05) improved absolute weight gain (AWG; 14.3–65.9 g fish^?1), feed conversion ratio (FCR; 5.9–1.5), protein retention efficiency (PRE; 6.2–32.2%), haemoglobin (Hb; 6.5 to 11.9 g dL^?1) and haematocrit (Hct; 23.5–33.8%). To determine the precise information on tryptophan requirement, data were subjected to broken‐line and second‐degree polynomial regression analysis. Broken‐line regression analysis reflected highest R² values for AWG g fish^?1 (0.999), PRE% (0.993), Hb g dL^?1 (0.995) and Hct% (0.993) compared with R² values obtained using second‐degree polynomial regression analysis of AWG g fish^?1(0.949), PRE% (0.890), Hb g dL^?1(0.969) and Hct% (0.943), indicating that data were better fit to broken‐line regression analysis. Hence, based on broken‐line regression analysis at 95% maximum response, tryptophan requirement of fingerling H. fossilis is recommended between 0.24% and 0.27% dry diet (0.63–0.71% protein).     

Prey consumption during development as well as longevity and reproduction of Typhlodromus pyri Scheuten (Acari, Phytoseiidae) at higher temperatures in the laboratory

The predatory mite Typhlodromus pyri Scheuten (Acari, Phytoseiidae) has been reported as an important predator of the European red mite, Panonychus ulmi (Koch) (Acari, Tetranychidae) in apple culture and vineyards at below 25°C. However, sufficient biological data was lacking on its efficiency at temperatures above 25°C. Therefore, the purpose of the present laboratory work was to obtain experimental data on prey consumption during development as well as longevity and reproduction of T. pyri on apple leaf discs and in Plexiglas cells at constant temperatures of 25±2°C and 30±2°C with P. ulmi as prey.The results showed that mean daily and total prey consumption by both the nymphs and adults of T. pyri decreased significantly on both the arenas as the temperature was increased from 25°C to 30°C, whereby adult prey consumption, both mean daily and total, was higher than that of nymphs. Prey consumption by both the nymphs and adults was significantly higher in the Plexiglas cells than on the leaf discs at both temperatures. Mean total prey consumption during nymphal development was 16.1 () and 12.8 () at 25°C compared to 7.0 () and 5.8 () preys at 30°C on the apple leaf discs and 46.0 () and 38.5 () at 25°C compared to 25.2 () and 20.3 () preys at 30°C in the Plexiglas cells. Mean duration of nymphal development was similar for the two sexes at the same temperature, but it was longer at 25°C than at 30°C. It was 6.0 and 4.0days on the apple leaf discs while 7.0 and 6.0days in the Plexiglas cells at 25°C and 30°C, respectively. Mean daily and total prey consumption by both male and female adults also decreased with the increasing temperature, whereby the females consumed more than double the mean total number of prey than the males on both the arenas of observation and at both temperatures: 355.4 versus 149.7 preys at 25°C and 192.2 versus 85.6preys at 30°C on the leaf discs and 826.8 versus 374.5 preys at 25°C and 488.9 versus 187.9 preys at 30°C in the Plexiglas cells. Longevity of the females was longer than males on both arenas and at both temperatures and it was longer at 25°C than at 30°C. Mean total longevity on the apple leaf discs was 68.3 () and 50.8 () days at 25°C compared to 52.5 () and 36.8 () days at 30°C, while in the Plexiglas cells it was 91.0 () and 65.8 () days at 25°C compared to 75.3 () and 48.5 () days at 30°C. Reproduction in females also decreased significantly with increasing temperature. It decreased from 62.0 to 39.0 eggs/female on the leaf discs and 75.0 to 47.1 eggs/female in the Plexiglas cells. The females laid significantly higher numbers of eggs at both temperatures in the Plexiglas cells than on the leaf discs. Oviposition period in females was 30days at 25°C on both the arenas, while at 30°C it was 26days on the apple leaf discs and 27days in the Plexiglas cells.     

Rising CO2 can alter fodder–weed interactions and suppression of Parthenium hysterophorus

Three C₄ grass (Setaria incrassata, Astrebla squarrosa and Bothriochloa decipiens) and one C₃ legume (Clitoria ternatea) suppressive fodder species, were re‐evaluated against the growth of the C₃ Parthenium hysterophorus under an ambient (390 μmol mol^?1) and an elevated atmospheric CO₂ concentration (550 μmol mol^?1). Under the elevated atmospheric CO₂, shoot dry biomass and suppression index (SI) value of the C₄ S. incrassata were both reduced by 32% and 0.7 respectively, while those for A. squarrosa were reduced by 23% and 0.3. In contrast and under the same elevated atmospheric CO₂ concentration, the shoot dry biomass and SI of the C₄ B. decipiens were increased by 8% and 0.1 respectively, while those for the C₃ C. ternatea were increased by 38% and 0.8. Our results suggest that C₃ fodder plants along with certain C₄ species could be utilised for the effective management of P. hysterophorus under the future elevated atmospheric CO₂ conditions. However, this system needs more fodder species to be investigated. Our results suggest that rising CO₂ per se may alter the efficacy of suppressive fodder management of an invasive C₃ species, P. hysterophorus.