International Journal of Plant Production
Volume:7 Issue: 1, Jan 2013

The grain yield (Y) of crops is determined by several Y components that reflect positive or negative effects. Conventionally, ordinary Y components are screened for the highest direct effect on Y. Increasing one component tends to be somewhat counterbalanced by a concomitant reduction in other component (s) due to competition for assimilates. Therefore, it has been suggested that components bemanipulated in conjunction with other traits to break the competition-resulting barrier. The objective of this study is to optimize the effective components in conjunction with certain participant traits for increased barley Y using an artificial neural network (ANN) and a genetic algorithm (GA) as an alternative procedure. Two field experiments were carried out separately at the Agriculture Research Station located in Gonbade Kavous (37 o16'' N, 55o12'' E and 37 asl), Iran. Ten genotypes were grown in each experiment, and the Y and certain traits/components were measured. Among the components/traits, those with a significant direct effect and/or correlation with Y were selected as effective for the ANN and GA analysis. The results indicate that the remobilization of stored pre-anthesis assimilates to grain(R 1), crop height (R2), 1,000-grains weight (R3), grain number per ear (R4), vegetative growth duration (R 5), grain-filling duration (R6), grain-filling rate (R7), and tiller number (R 8) were effective. The R2 for the training and est phases was 0.99 and 0.94, respectively, which reveals the capability of the ANN to predicting Y. The optimum values obtained by GA were 14.2%, 104.34 cm, 36.9 g, 41.9, 100 d, 48 d, 1.22 mg seed-1 day-1, and 3.38 plant-1 for R1 through R8, respectively. The optimization increased the potential Y to 5791 kg ha -1, which was higher than that observed for the genotypes (3527 to 5163 kg ha -1).

In order to evaluate the impact of crop residues (zero, 25 and 50%) and nitrogen (zero, 125 and 250 kg ha) on weed seed bank and potato yield, two-years research was conducted as a split plot arranged in randomized complete block design in Rozveh Agriculture Research Station, Freidan-Esfahan. Numbers of weed species in seed bank, aboveground, and both seed bank and aboveground were 1, 2 and 8 respectively. Amaranthus retroflexus L. was dominant weed in seed bank in the both years. Weed seed bank was significantly lower in both N rates than control in the both years with no significant difference between the rates. Weeds biomass with increased use of nitrogen fertilizer increased. In 25 and 50 percent of crop residue treatments, weed seed density was greater than control. 125 kg N ha -1 with 25 percent of crop residue treatment produced the highest tuber yield (27850 kg ha-1), although weed biomass was also high in this treatment. The results showed that management of nitrogen fertilizer application and weed control by applying crop residue crops in rotation will change.

Partial root-zone drying or partial root-zone irrigation is a newly proposed water saving technique which may improve water use efficiency and nutrient uptake by a crop without affecting its yield. A study was conducted to investigate the response of furrow-irrigated okra to partial root zone drying in relation to cropevapotranspiration (ETc), vegetative growth, yield, and nutrient use efficiency in a sandy loam soil. The experiment was conducted during December-March with three furrow irrigation strategies: alternate partial root-zone irrigation (APRI), fixed partial root-zone irrigation (FPRI), and full root-zone irrigation (FRI). Two levels of irrigation: 25% available soil moisture depletion (ASMD) and 50% ASMD were imposed under each furrow treatment. The plant vegetative growth was significantly (P<0.05) higher in FRI, whereas the pod yield was more in APRI. Lower depletion soil water treatment produced higher vegetative growth and yield. However, APRI at 50% ASMD resulted in highest irrigation water use efficiency (IWUE) for pod yield, and FPRI at 25% ASMD resulted in highest IWUE for total biomass. The maximum ETc was observed under FRI, followed by APRI. The crop co-efficient (Kc) values of 0.38, 0.74, 0.98 and 0.49 may be used in initial growth stage, mid growth stage, final growth stage, and maturity stage of okra, respectively, to estimate the volume of irrigation water under APRI. Partial factor roductivity for the nutrients (N, P and K) followed the similar trend as pod yield. Root biomass of the crop was more in FPRI, where as total root length was more in APRI. The higher root length with finer roots, in conjunction with better nutrients availability in soil produced the higher nutrients content in leaves and pods of alternate partially irrigated plants. Overall, these results reveal that the application of optimum quantity of water through APRI at 50% ASMD could impose desirable water stress on okra plants, improving their fruit yield and quality, without producing higher vegetative growth.

Yield variability of selected winter wheat cultivars under different sowing rate and selected application, was investigated during 2006-2008, in the Lower Silesia region (South-West Poland). Experiments with two varieties, two levels of sowing rate and seven herbicides, including untreated object were set up on the same field, using split-plot method. For evaluation of yield stability Kang''s yieldstability statistic (YS) was applied. Examined herbicides did not influence grain yield of both cultivars, at standard wheat density (450 seeds/m 2). Under low density, Kobra Plus variety showed variable reaction to herbicides. Iodosulfuron methyl sodium + diflufenican + mezosulfuron methyl, mecoprop + MCPA + dicamba and iodosulfuron methyl sodium + amidosulfuron resulted in yield increment in comparison with untreated object, whilst dicamba + triasulfuron gave opposing effect. Yield stability at different herbicide objects during 3-years period was considerably variable and dependent on cultivar and sowing rate. Yield of both cultivars, obtained from plots treated with iodosulfuron methyl sodium + diflufenican + mezosulfuron methyl, iodosulfuron methyl sodium + amidosulfuron and mecoprop + MCPA + dicamba, under low density was comparable with standard sowing.

We assessed changes in ultrastructure, membrane lipid peroxidation and antioxidant systems for cucumbner seedlings subjected to low temperature stress (day/night temperature of 8 oC /5 oC) that had been either pre-treated with 10% PEG for 2 days or not. We found extensive cell structure damage in the non-treated seedlings, whereas the seedlings pretreated with PEG to simulate drought remained essentially undamaged, except for slight damage to plasma membrane lipids and alveolation in the mitochondria. Low temperature stress increased electrolyte leakage, MDA levels and H 2O2; decreased the activities of SOD, CAT and APX, and AsA and GSH content. An increase in POD activity was observed in the PEG-pretreated seedlings during the chilling period, while non-treated seedlings showed an increase in POD activity only in the early days of chilling stress. PEG pre-treatment diminished the level of lipid peroxidation caused by chilling compared to the non-treated seedlings, possibly due to a decrease in electrolyte leakage and MDA content. Furthermore, PEG pre-treatment increased the activities of SOD, POD, CAT and APX and AsA and GSH content in the chilling-stressed seedlings. These results suggest that PEG pre-treatment stimulates the adaptation of cucumber to low temperature. This could be due to stabilisation of the cell structure, alleviation of lipid peroxidation as a result of the increased activity of antioxidant enzymes and contents of antioxidant metabolites.

Drought affects yield of peanut, but its effect on oleic and linoleic acids that influence its oil quality of peanut genotypes with different levels of drought resistance has not been clearly investigated. Therefore, the aims of this research were to determine whether soil water levels could affect oil quality by changes in fatty acid compositions of peanut, and to investigate the changes in oil characters in peanut genotypes with their potential drought resistance under different water regimes. Field experiments were conducted in split-plot designs with four replications during dry season for two years (2003/04 and 2004/05). Three water regimes [field capacity (FC), 2/3 available soil water (2/3 AW) and 1/3 available soil water (1/3 AW)] were assigned as main-plots, and six peanut genotypes were assigned as sub-plots. The data were recorded at maturity for fatty acid compositions and % oil. Seed samples were analyzed for % oil by Soxtec System HT, and fatty acid compositions were analyzed by gas liquid chromatography. Differences among water regimes and peanut genotypes were significant for oleic and linoleic acids content and their ratio (O/L ratio), unsaturated to saturated fatty acid ratio (U/S ratio) and iodine value (IV). Genotype × water regime interactions were also significant for all characters. Drought improved the oil quality by significant increase in oleic acid and O/L ratio, and reduced the linoleic acid, IV and U/S ratio. Peanut genotypes with different levels of drought resistance displayed similar tendency in fatty acid characters under drought conditions.

The remobilization of water soluble carbohydrates (WSC) has an important role for grain yield. This study investigated the accumulation and remobilization of WSC in non-leaf organs (chaff, upper stem, and lower stem) and their contribution to grain yield, under different irrigation levels (rainfed, reduced irrigation, and full irrigation) and seeding rate treatments (450, 600 and 750 plants m -2) using two winter wheat cultivars, Shijiazhuang 8 (SJZ-8) and Lumai 21 (LM-21), in two field experiments. Results showed that decreasing irrigation and increasing seeding rates increased WSC accumulation and remobilization, remobilization efficiency, and contribution to grain yield in non-leaf organs. When the organs are ranked from highest to lowest in terms of the WSC accumulation amount, remobilization amount, remobilization efficiency, and contribution to grain yield, they are: the lower stem, the upper stem, and then the chaff. And between cultivars, these amounts were higher in SJZ-8 than in LM-21. The total contribution, pre-anthesis contribution, and post-anthesis contribution of WSC remobilization from all non-leaf organs to grain yield ranged from 11.7 to 21.5%, 4.8 to 9.4%, and 6.9 to 12.1%, respectively. This increase in WSC accumulation, remobilization, and contribution to grain yield in non-leaf organs is an important reason high grain yields can be maintained in water-saving and optimal high density management systems.

Crop depends on its canopy to intercept solar radiation to drive both assimilation and water, nutrient absorption for its growth. Field experiments, involving three sowing time and three sowing rate, were conducted at Luancheng Station to investigate the effects of canopy size and development on crop growth and radiation use efficiency (RUE) of winter wheat during 2009/2010 and 2010/2011 growing seasons. The results showed that the maximum effects of sowing time on the phenological development occurred between emergence and elongation, and which was 186.0 and 162.3 d oC thermal time difference during 2009/2010 and 2010/2011, respectively. Sowing time and sowing rate significantly affected above-ground biomass accumulation and RUE. Results showed that optimized sowing time and sowing rate has the potential to improve yield of winter wheat and radiation use efficiency. RUE during pre-anthesis was lower than that during post-anthesis, especially for the delayed sowing treatments which was mainly caused by the lower dry matter mobilization (DMM) and dry matter mobilization efficiency (DMME). Compared with the normal sowing time treatment, the delayed sowing time treatments had the lower DMM and DMME which indicated that the different sowing date would affect the duration of growth and then the RUE.

This work presents information on the patterns of yield determination by yield components as a function of the level of management of the crop. The data used for the analyses were obtained from 8 field experiments located across Poland in 2009 and 2010. 25 winter wheat cultivars were evaluated at two management levels, i.e., at a low input of nitrogen fertilisation and pesticides and at a higher input of these materials. Yield determination was evaluated with a path analysis conducted for each cultivar separately for each management level. The results were presented using the values of the path coefficients. The pattern of yield determination for most of the cultivars examined differed between the high-input and the low-input management levels. Under the low-input management, all three yield components contributed similarly to yield determination. Under high-input management, the effect of the number of spikes per m 2 was much greater than the effect of the weight of an individual grain.

Thymus daenensis is a medicinal plant endemic to semi-arid regions of Iran. A field experiment using a randomized complete block design with four replications was conducted to evaluate the effect of 20, 50 and 80% soil water depletion on morpho-physiological traits, essential oil content and composition and water use efficiency of T. daenensis during 2010-2011. Water stress reduced growth, herbage roduction, chlorophyll and carotenoid content, while increased proline, K +, essential oil content and irrigation water use efficiency based on essential oil yield (IWUE eso). Thymol was the highest essential oil composition (63.3-73.5%) followed by carvacrol (3.6-16.0%), ρ-cymene (3.8-7.4%), γ-terpinene (3.3-4.7%), β -caryophyllene (2.8-4.0%) and borneol (1.4-3.4%), respectively. Thymol, ρ-cymene and γ-terpinene were increased, while the other compositions decreased under water stress. It is concluded that irrigation of T. daenensis based on 50% water depletion should be an appropriate choice for first growing season and 80% water depletion for the second growing season in semi-arid climatic conditions.