Effect of Heat Stress for Agro-Economic Traits in Bread Wheat (Triticum Aestivum L.) Genotypes

In the scenario of increasing global warming, heat stress received more importance. Un- fortunately, Pakistan is also in the line of most heat affected countries of the world. In this regard, wheat being a most important staple edible crop of Pakistan is highly affected by heat stress. For combating this situation, a study was carried-out on ten bread wheat genotypes viz. Moomal, Mehran, Imdad-05, Anmol- 91, Benazir, TJ-83, SKD-1, TD-1, Abadgar and Hamal at the Experimental Field, Department of Plant Breeding and Genetics, Sindh Agriculture University, Tandojam. The experiment was laid-out in a randomized complete block design (factorial arrangement) with three replications during Rabi season, 2016-17 in order to assess the response of wheat genotypes to terminal heat stress tolerance. Wheat genotypes were evaluated in two sowing dates viz., on 24th November as a normal planting and late planting on 31th December, 2016 considered as heat stress condition. The analysis of variance revealed significant differences among the genotypes under both sowing dates indicating suitability of the experiment to improve bread wheat genotypes for heat tolerance. Reductions in various traits were observed in late planting which indicated visible effects of heat stress on agro-economic traits. On an average plant height (cm), tillers/plant, spike length (cm), spikelets/spike, grains/spike, 1000-grain weight (g) and grain yield/plant (g) were declined by -4.63, -2.49, -3.04, -4.35, -16.29, -14.08 and -9.09 units respectively under the heat stress conditions, while the wheat genotypes like TJ-83, SKD-1 and Mehran showed minimum reductions under heat stress conditions for various traits suggesting their heat tolerance, nonetheless cultivars Moomal and Benazir expressed maximum declines under heat stress expressing their susceptibility to heat stress conditions. The remaining genotypes were found as moderately heat stress tolerant.

Effect of nitrogen scheduling in early and late planted medium duration rice (Oryza sativa L.)

A field experiment on rice (Oryza sativa L.) crop was conducted at Rice Research Station, Kaul (Kaithal), India during kharif season of 2017 and 2018 to evaluate the optimum schedule of nitrogen application in the rice grown under early and late planting conditions. The treatments consisted of three timings of transplanting (3rd week of June, 1st week of July and 3 rd week of July), four levels of N (90, 120, 150 and 180 kg Nha-1) and four timings of N fertilizer application (½ at transplanting + ½ at 21 DAT, ½ at 21 DAT + ½ at 42 DAT, 1/3 at transplanting + 1/3 at 21 DAT + 1/3 at 42 DAT and LCC based N supply) and were laid out in split-plot design with transplanting time and N levels in main plots and N application time in sub-plots. The growth parameters (plant height, number of tillers/m2 and dry matter accumulation/m2), yield attributing characters (number of panicles/m2 and grains/panicle) and yield (grain and straw yield) of rice crop reduced significantly under late planting (3rd week of July) as compared to that under the two earlier plantings (3rd week of June and 1stweek of July) whereas the two earlier plantings were at par in respect of these parameters. The growth, yield attributes and the yield increased with every increase in N application rates but the increase was significant up to 150 kg Nha-1. The highest yield was (7.33 tha-1), however, obtained with the crop transplanted early (up to1st week of July) and supplied with 150 kg Nha-1.Application of N in three equal splits (at 0, 21 and 42 DAT or as per LCC schedule), being at par, resulted into higher yield (grain and straw) than the N application in two equal splits. The net returns and B: C ratio increased appreciably with increase in N application levels upto 150 kg Nha-1 obviously due to increase in crop yield.

Effect of planting time and row spacing on growth and seed production of junglerice (Echinochloa colona) and feather fingergrass (Chloris virgata) in sorghum

Junglerice and feather fingergrass are major problematic weeds in the summer sorghum cropping areas of Australia. The objectives of this study were to investigate the growth and seed production of junglerice and feather fingergrass in crop-free (fallow) and under competition with sorghum planted in 50 cm and 100 cm row spacings at three sorghum planting and weed emergence timing. Results revealed that junglerice and feather fingergrass had greater biomass in early planting (November 11) compared with late planting time (January 11). Under fallow conditions, seed production of junglerice ranged from 12,380-20,280 seeds plant−1; with the highest seed production for the December 11 and lowest for the January 11 planting. Seed production of feather fingergrass under fallow conditions ranged from 90,030 to 143,180 seeds plant−1. Seed production of feather fingergrass under crop-free (fallow) was similar for November 11 and December 11 planting, but higher for the January 11 planting. Sorghum crop competition at both row spacings reduced the seed production of junglerice and feather fingergrass >75% compared to non-crop fallow. Narrow row spacing (50 cm) in early and mid- planted sorghum (November 11 and December 11) reduced the biomass of junglerice to a greater extent (88%-92% over fallow grown plants) compared with wider row spacing (100 cm). Narrow row spacing was found superior in reducing biomass of feather fingergrass compared with wider row spacing. Our results demonstrate that sorghum crops can substantially reduce biomass and seed production of junglerice and feather fingergrass through crop competition compared with growth in fallow conditions. Narrow row spacing (50 cm) was found superior to wider row spacing (100 cm) in terms of weed suppression. These results suggest that narrow row spacing and late planting time of sorghum crops can strengthen an integrated weed management program against these weeds by reducing weed growth and seed production.

Key factors involved in reduction of damage to sunflower by the European sunflower moth in China through late planting

The European sunflower moth, Homoesoma nebulellum (Denis et Schiffermüller), emerged as a major new pest in Bayannur, China, in 2006. Insecticidal control with a single application is problematic because timing is critical, and multiple applications increase production and environmental costs. Management of H. nebulellum by planting date adjustment can be effective, but the optimal time window for late planting is unknown. Natural levels of H. nebulellum infestation were compared among sunflowers planted on five dates from April 25 to June 5 in two years, and the relationship between timing of adult abundance and flowering assessed. Delaying planting of sunflower from the traditional planting period of April 25 –May 5 to May 15 –June 5 significantly decreased damage by H. nebulellum. Seed infestation rate was 30–40 times higher, and number of larvae/head 75–100 times higher in the earliest two plantings than in the latest two. Within two years of implementing delayed planting in Bayannur city, infestation area decreased from 72% in 2006 to 1.5% in 2008, and production losses decreased from 4.5 ton/ha in 2006 to 0.36 ton/ha in 2008, a 97% decrease compared to 2006. Moreover, the infestation area caused by H. nebulellum was continuously controlled below 5.3% of the planting area since 2008. We found the overlap between the first two days of flowering and peak adult presence was the key factor influencing level of damage caused by H. nebulellum. Because the number of eggs laid in the first two days of flowering accounted for 68% of the total, and sunflower seed infestation rate was positively correlated with the number of trapped adults weighted by proportion of daily oviposition. Oviposition of the majority of eggs in the first two days of flowering suggests an evolutionary mechanism whereby females choose host plants most conducive to larval development, consistent with the preference-performance hypothesis.

Integrated Weed Management Systems to Control Common Ragweed (Ambrosia artemisiifolia L.) in Soybean

As resistance to herbicides limits growers' weed management options, integrated weed management (IWM) systems that combine non-chemical tactics with herbicides are becoming critical. A 2 year integrated weed management (IWM) study was conducted at three locations in VA, USA. The factorial study evaluated: (1) soybean planting date (early or late planted) (2) with or without winter cover (cereal rye/wheat or no cover), and (3) with or without harvest weed seed control (HWSC). Prior to soybean planting in the first year, winter cover resulted in a 22% reduction in common ragweed density compared to no cover. At soybean harvest in the first year, the lowest common ragweed densities were in the late planted plots following winter wheat, and common ragweed aboveground biomass was reduced by 46 and 22% at two locations in late planted compared to early planted soybean. To evaluate the impact of the first year's treatments and HWSC, full season soybeans were planted across the trial in the second year. Prior to soybean planting in the second year, late planting in the first year common ragweed density was reduced by 83% at one location, but significant reductions were not observed elsewhere. When comparing winter cover to no cover, common ragweed densities were reduced by 31 and 49% at two locations and densities were similar at the third location. Harvest weed seed control reduced common ragweed density by 43% at one location compared to the conventional harvest plots but no significant reductions were observed at the other locations or at other rating timings. However, there was a significant location by planting date by winter cover interaction and the overall lowest common ragweed densities (4.1 to 10.3 plants m−2) were in the late planted plots with winter cover. This research indicated that winter cover, late planting, and HWSC can reduce common ragweed populations with late planting being the most influential. Therefore, double-cropping soybean after wheat is likely the most viable means to better control common ragweed using IWM as it combines both winter cover and late planting date.