Evaluation of sunflower (Helianthus annuus L.) single cross hybrids under heat stress condition

Sunflower is an important oilseed crop, which shows susceptibility to heat stress. In this study, 63 single cross hybrids were evaluated under heat stress condition for 2 years and compared with the two commercial hybrids. Genotype and genotype × environment (GGE) was used to differentiate single cross hybrids on the basis of multiple traits. GGE biplot showed that several single cross hybrids had higher seed yield potential than standard check. Moreover, seed yield per plant (SYP) was related to pollen viability percentage, showing that achene yield was the product of high gametophytic fertility under heat stress. Hybrids having high seed yield potential under heat stress had lower cell membrane injury. GGE biplot for SYP and its components showed that single cross hybrids were characterized into two major groups. Group I was further characterized into two sub group. Group Ia included hybrids with high 100-SW, while group Ib had the hybrids with high number of seeds per head and head diameter. Group II had the hybrids with high kernel weight and kernel to seed ratio. The hybrids could be recommended according to their potential utilization in the seed industry.     

Yields of Green Grams and Pigeonpeas under Smallholder Conditions in Machakos County,Kenya

Green grams and pigeonpeas have multiple benefits to the rural poor as food security, fodder for livestock and fuel for small-scale farmers, despite low smallholder yields in Kenya. However, little is known about the factors between different farmers that influence the yields of green grams and pigeonpeas. The objectives of this study therefore were to describe and compare how the groups of farmers in agro-ecological zones (AEZs) LM 4 and LM 5 differ by their yields of green grams and pigeonpeas and to estimate the parameters of the variables which explain the yields. Data collection was through a well-structured questionnaire, administered to 364 respondents, selected through a multi-stage sampling technique. Each AEZ had an equal sample size (182 respondents). One-way analysis of variance (ANOVA) and multiple linear regression were used during data analysis. The ANOVA results showed that the mean of the green gram yields in AEZs LM 4 and LM 5 was 19.90 and 173.67 kg ha^?1 while the mean of the pigeonpea yields was 109.26 and 34.01 kg ha^?1, respectively. The multiple linear regression model results showed that the green gram yields were positively related to the use of improved seed (p?=?0.001), cultivated farm sizes (p?=?0.011), green gram crop intensity (p?=?0.005), oxcart (p?=?0.003) and agro-ecological zone (p?=?0.000). The farmer differences in the use of improved seed were found to be significantly and positively related to the yields of pigeonpeas (p?=?0.057), while the sizes of the cultivated farms (p?=?0.057) and the agro-ecological zones (p?=?0.000) showed inverse relationships (IRs). Based on the given research evidence, it was therefore concluded that the groups of farmers in AEZs LM 4 and LM 5 have different yields of green grams and pigeonpeas and there are factor gaps in productivity.     

辣椒热泵干燥特性及工艺参数优化

为了提高干制辣椒品质,降低干燥能耗,该文应用热泵干燥技术干燥辣椒。首先探究干燥温度和铺料厚度对干燥特性的影响,绘制出含水率和干燥速率变化曲线。在此基础上,将分阶段控温和改变铺料厚度结合起来对辣椒进行热泵干燥,运用响应面法中的Box-Behnken设计,考察第一阶段温度、第二阶段温度、铺料厚度和三者的交互作用对品质得分、单位能耗、干燥时间的影响,并建立回归方程,得出最佳工艺参数。结论如下:温度越高,干燥速率越大,含水率下降越快;铺料厚度越大,干燥速率越小,含水率下降越慢;第一阶段温度是影响单位能耗的主要因素(P0.05),较低的第一阶段温度能降低单位能耗;第二阶段温度对品质得分影响显著(P0.05),对干燥时间影响极显著(P0.01),第二阶段温度在60℃左右时能得到品质较佳的干辣椒,且在一定程度上提高了干燥效率;铺料厚度对品质得分、干燥时间的影响极显著(P0.01),对单位能耗的影响显著(P0.05),铺料厚度在45 mm左右干燥获得的辣椒品质较佳,而且能节约能耗,提高干燥效率。综合优化参数为:第一阶段温度48℃、第二阶段温度61℃、铺料厚度44 mm,在此工艺条件下获得的干燥辣椒品质得分为8.64,单位能耗为92.05 k J/kg,干燥时间为896.02 min。研究结果为热泵干燥技术应用于辣椒干制提供参考。     

Accumulation and distribution of Zn and Mn in soybean seeds after nutrient seed priming and its contribution to plant growth under Zn- and Mn-deficient conditions

Nutrient seed priming is a strategy to increase the seed reserves of mineral nutrients as primary source for mineral nutrition during seedling development and early growth. The present study investigates the effects of zinc (Zn) and manganese (Mn) seed priming on growth and nutritional status of soybean under conditions of Zn and Mn limitation. Nutrient seed priming increased the natural seed reserves for Zn by, approximately, sixfold and by fivefold for Mn; however, 40–60% of the primed nutrients were adsorbed to the seed coat. Zinc seed priming was able to maintain plant growth for 5 weeks in the same way as Zn supply via the nutrient solution. It is concluded that nutrient seed priming offers perspectives to improve seed quality of soybean for early seedling development under limited nutrient supply or availability and needs further investigation on performance under various stress conditions.     

Polymer coated DAP helps in enhancing growth,yield and phosphorus use efficiency of wheat (Triticum aestivum L.)

Low phosphorus use efficiency (PUE) is one of the major reasons of poor wheat production worldwide. Among the various approaches used to enhance PUE, polymer coated fertilizers are relatively a new concept. Keeping this in view, a field study was conducted to evaluate polymer coated di-ammonium phosphate (DAP) to enhance growth, yield and PUE of wheat. Commercial DAP and polymer coated DAP (50%, 75% and 100% of recommended dose) were tested in wheat. Results revealed that application of 50% polymer coated DAP produced the same results or higher than 100% commercial DAP. However, the maximum increase in growth (plant height, root length, number of tillers m^?2, inter-nodal distance), yield (number of grains per spike, 1000 grain weight, grain yield and biological yield) and phosphorus acquisition by wheat was observed with 100% polymer coated DAP. Moreover, 100% polymer coated DAP increased phosphorus recovery and agronomic efficiency compared to other treatments.     

Effect of biochar-amended urea on nitrogen economy of soil for improving the growth and yield of wheat (Triticum Aestivum L.) under field condition

A field experiment was conducted to evaluate effect of biochar-amended urea on nitrogen economy of soil for improving the growth and yield of wheat under field condition. Experiment plan was comprised of twelve treatments with four replications including treatments without application of urea and biochar (control) and urea only. Biochar was applied at 1–10% of the weight of urea fertilizer applied each treatment. Results showed that application of biochar at 10% with recommended dose of urea significantly improved plant height, spike length, number of tillers, number of spikelet per spike, 1000 grain weight, grain yields, biomass yield, harvesting index, nitrogen (N) concentration and uptake in grain and straw, and agronomic efficiency of nitrogen by 6.0%, 11.1%, 32.0%, 55.3%, 5.4%, 38.0%, 19.0%, 9.0%, 19.0%, 26.0%, 65.0%, 50.0%, and 63.0%, respectively, as compared to treatment comprised of recommended rate of nitrogen without biochar.     

Evaluation and management of acetyl-CoA carboxylase inhibitor resistant littleseed canarygrass (Phalaris minor) in Pakistan

A field survey was conducted for the sampling of Acetyl-CoA carboxylase (ACCase) inhibitor resistance littleseed canarygrass, a major weed of wheat, from Punjab, Pakistan in 2014 for confirmation of resistance. The surveyed regions encompassed four different cropping systems including rice–wheat, maize–wheat, cotton–wheat and mixed cropping. Dose–response assay was conducted for confirmation of resistance. Efficacy of herbicide mixtures including clodinafop–propargyl, metribuzin, pinoxaden and sulfosulfuron at a range of doses was investigated to manage littleseed canarygrass. Results revealed that all populations were resistant to fenoxaprop except PM-BWL-2. The higher level resistance (6.5) was found in populations collected from rice–wheat cropping system. The tested herbicide mixtures at 75% and 100% of the recommended dose of each mixture component provided the effective control of resistant littleseed canarygrass. Mixtures at 50% provided more than 80% control and reduced growth and seed production potential of surviving plants. The confirmation of ACCase inhibitor resistance as the first case of herbicide resistance in Pakistan, leads us to discourage use of ACCase inhibitor herbicides alone. However, herbicide mixtures at 75% and 100% of the recommended dose are suggested to manage this weed for sustainable wheat production in the surveyed cropping systems.     

Growth and physiology of basmati rice under conventional and water-saving production systems

Conventionally flooded rice (CFR) requires enormous water and labor inputs. Water scarcity aspires for cultivation of water-saving rice. Growth response and physiology of basmati rice genotypes under the water-saving production systems has not been reported yet. Studies were conducted for 2 years to compare the growth and physiology of three rice cultivars (Super Basmati, Basmati-2000 and Shaheen Basmati), under high (CFR), medium (alternate wetting and drying [AWD]) and low water input (aerobic rice [AR]) systems. Leaf area index, crop growth rate, leaf area duration and dry matter accumulation were higher for AR followed by AWD and CFR, respectively. Shaheen Basmati had a lower growth and relative water contents than Super Basmati and Basmati-2000, probably due to its shorter stature and shorter life cycle. Photosynthetic rate and stomatal conductance of rice cultivars in the different production were affected only at reproductive stage. Basmati-2000 grown as AR had the highest photosynthetic rate followed by the same cultivar under AWD. The results of this study provide us an idea that basmati cultivars can attain a high growth and development with low water input. This would be helpful to grow rice successfully under water-short rice-growing environments.     

Landuse impacts on soil organic carbon fractions in different rainfall areas of a subtropical dryland

Landuse can alter soil organic carbon (SOC) fractions by affecting carbon inflows and outflows. This study evaluated changes in SOC fractions in response to different landuses under variable rainfalls. We compared cropland, grassland and forest soils in high rainfall (Islamabad ~1142 mm) and low rainfall (Chakwal ~667 mm) areas of Pothwar dryland, Pakistan. Forest soils in both rainfall areas had highest SOC (11.32 g kg^?1), particulate organic carbon (POC, 1.70 g kg^?1), mineral-associated organic carbon (MOC, 7.17 g kg^?1) and aggregate-associated organic carbon (AOC, 7.86 g kg^?1). However, in rangeland and cropland soils, these varied with rainfall. Under high rainfall, SOC and MOC were 12% and 17% higher in rangeland than in cropland while POC and AOC were equal. Under low rainfall, SOC and MOC were higher in rangeland than in cropland by 7.21 and 1.79 g kg^?1 at 0–15 cm and equal at 15–30 cm depth. POC and AOC were higher in rangeland than in cropland, in both depths. Averagely, SOC, POC, MOC and AOC were 26%, 68%, 76% and 30% higher in high rainfall than in low rainfall soils. Sensitivity of SOC fractions to landuses observed under different rainfalls could provide useful information for soil management in subtropical drylands.