International Journal of Plant Production
Volume:5 Issue: 3, Jul 2011

Water stress causes defoliation, which can reduce yield and root quality of sugar beets (Beta vulgaris L.) through altered gas exchange characteristics of the leaves. In a two-year experiment, three sugar beet cultivars (Europa, Rival and Corsica) were subjected to three defoliation levels (control-C, moderate-MD, severe-SD) and re-watering after their exposition to drought for a month. Leaf physiological traits including net photosynthesis (A), transpiration rate (E), stomatal conductance (gs), intracellular CO2 (Ci), water use efficiency (WUEL-A/E and WUEi-A/gs), leaf N concentration, petiole NO3-N concentration, specific leaf area (SLA), leaf water potential (WP) and leaf water content (LWC), were determined before defoliation and 15, 30 and 40 days after defoliation (DAD). On contrary to previous reports, water-stressed cultivars differed significantly in their leaf physiology; the late-season cultivar Corsica had the lowest E and gs values without any significant reduction in A. Thus, Corsica was the most water-conservative cultivar. Re-watering rapidly restored leaf physiology but a gradual decline, with the progress of DAD, was evident for A, E, gs and Ci. After re-growth, cultivars differed only in WP and LWC with Europa, the early-harvested cultivar, to have the highest values. Thus, the better response (higher yield increase and lower root quality degradation) of Corsica to re-watering and the subsequent re-growth, as reported by Tsialtas et al. (2009), could be ascribed to its better LAI maintenance compared to Europa and Rival rather than to a better leaf physiological response. The SD plants showed the highest leaf physiological activity since they had the highest A, E, gs and leaf N concentration. The high leaf activity and the low respiration rate are the means by which sugar beets tolerate foliage losses up to 75% and compensate yield losses after defoliation

.In this study, the effects of concentration and application time of ethephon on growth parameters; stem height, stem diameter, biomass, carbohydrate content; sucrose content, invert sugar, brix value, and juice volume of two sweet sorghum cultivars were determined. Three ethephon application time (8 leaves, booting, and flowering) and five ethephon concentrations (0, 200, 400, 600, and 800 ppm) on two sweet sorghum cultivars (Sofra and Keller), were deigned in a split-split plot with three replications. Hormone application time assessed as main plot, cultivars as sub plot and ethephon concentrations as sub-sub plots. Brix was shown the maximum amount (16.7%) at booting stage while it was not significant at the other two stages of hormone application time (15%). The lowest biomass was (21.5 t ha-1) at 8 leaves stage and the highest (46 t ha-1) at flowering stage. Similar to biomass the lowest juice volume was (3650 L ha-1) at the 8 leaves stage of the hormone application time and highest (8000 L ha-1) at the flowering. Sucrose content was significantly affected (P<0.01) by the treatment. It was higher at booting stage (11.84%) than both 8 leaves stage and flowering stage (10.7%). cv. Keller had higher stem height, brix, and sucrose content than Sofra while its invert sugar was lower than Keller. Based on these results, to have the highest brix value it may be suggested to apply ethephon at 800 ppm at flowering stage in both sweet sorghum Keller and sofra cultivars.

Cotton (Gossypium hirsutum L.) seeds are susceptible to low temperature and excess moisture in soil during seed emergence in years with high rainfall and low temperature in spring. Therefore, a two-year field experiment was carried out to evaluate effects of ridge tillage formed in autumn (RT-I), ridge tillage formed about a month before planting (RT-II) and flat conventional tillage (CT) cultivation systems on physical properties of soil and cotton growth. The RT-I and RT-II resulted in higher soil temperature and lower soil penetration resistance than CT at all depths. The RT-II gave highest emergence, earliest maturity and greatest seed cotton yield. In conclusion, ridge tillage formed a month before planting may be considered a good agronomic practice because it can provide favorable physical conditions in soil, while also improving growth and yield of cotton under weather conditions in spring in South East Anatolia Region of Turkey.

Effects of six tillage practices on some soil microbiological properties and crop yields were evaluated for a clay soil (Typic Haploxererts) under semi-arid Mediterranean conditions in a three year study (2006-2009). The experiment was designed as a completely randomized-block with three replications. Treatments were: conventional tillage with residue incorporated (CT1), conventional tillage with residue burned (CT2), reduced tillage with heavy tandem disc harrow (RT1), reduced tillage with rotary tiller (RT2), reduced tillage with heavy tandem disc harrow for the first crop + notillage for the second crop (RNT), and no tillage (NT). The study was conducted in wheat-corn, wheat-soybean and wheat crop rotations. Dehydrogenase activity, soil respiration, mycorrhizal spore number, total organic carbon (TOC), and total N were determined at three depths (0-10, 10-20 and 20-30 cm). The mycorrhizal spore number responded quite early to tillage practices. Significant tillage effects on TOC and total N were observed only at 0-10 cm depth. The TOC content was increased by NT, RT2, RNT and RT1 practices compared to the initial values at the same depth as 74%, 62%, 56%, and 50%, respectively. Dehydrogenase activity (DHA) and soil respiration were higher on the surface and decreased with depth. Reduced and no-tillage practices significantly increased the mycorrhizal spore number, dehydrogenase activity and soil respiration at all depths (P<0.05). Both CT1 and CT2 practices had significant negative effects on all measured soil properties. Tillage practices had no significant effect on crop yields except for the wheat yield in 2008. The results indicated that, as an alternative to conventional tillage, reduced and no-tillage practices provided successful crop production in a clay soil under a semi-arid climate.

Effects of six tillage practices on some soil microbiological properties and crop yields were evaluated for a clay soil (Typic Haploxererts) under semi-arid Mediterranean conditions in a three year study (2006-2009). The experiment was designed as a completely randomized-block with three replications. Treatments were: conventional tillage with residue incorporated (CT1), conventional tillage with residue burned (CT2), reduced tillage with heavy tandem disc harrow (RT1), reduced tillage with rotary tiller (RT2), reduced tillage with heavy tandem disc harrow for the first crop + notillage for the second crop (RNT), and no tillage (NT). The study was conducted in wheat-corn, wheat-soybean and wheat crop rotations. Dehydrogenase activity, soil respiration, mycorrhizal spore number, total organic carbon (TOC), and total N were determined at three depths (0-10, 10-20 and 20-30 cm). The mycorrhizal spore number responded quite early to tillage practices. Significant tillage effects on TOC and total N were observed only at 0-10 cm depth. The TOC content was increased by NT, RT2, RNT and RT1 practices compared to the initial values at the same depth as 74%, 62%, 56%, and 50%, respectively. Dehydrogenase activity (DHA) and soil respiration were higher on the surface and decreased with depth. Reduced and no-tillage practices significantly increased the mycorrhizal spore number, dehydrogenase activity and soil respiration at all depths (P<0.05). Both CT1 and CT2 practices had significant negative effects on all measured soil properties. Tillage practices had no significant effect on crop yields except for the wheat yield in 2008. The results indicated that, as an alternative to conventional tillage, reduced and no-tillage practices provided successful crop production in a clay soil under a semi-arid climate.

Nitrogen (N) uptake (kg ha-1) of field-grown potatoes was measured in 4.32 m2 lysimeters that were filled with coarse sand, loamy sand, and sandy loam and subjected to full (FI), deficit (DI), and partial root-zone drying (PRD) irrigation strategies. PRD and DI as water-saving irrigation treatments received 65% of FI after tuber bulking and lasted for six weeks until final harvest. Results showed that the irrigation treatments were not significantly different in terms of N uptake in the tubers, shoot, and whole crop. However, there was a statistical difference between the soil textures where plants in the loamy sand had the highest amount of N uptake. The interaction between irrigation treatments and soil textures was significant, and implied that under non-limiting water conditions, loamy sand is the suitable soil for potato production because plants can take up sufficient amounts of N and it could potentially lead to higher yield. However, under limited water conditions and applying water-saving irrigation strategies, sandy loam and coarse sand are better growth media because N is more available for the potatoes. The simple yield prediction model was developed that could explains ca. 96% of the variations of fresh tuber yield based on the plant evapotranspiration (ET) and N uptake in the tuber or whole crop.

Soil contamination with potentially toxic elements (PTEs) in agricultural lands, in part, is responsible for limiting the crop productivity and the food chain contamination. The objective of this study were to asses the limiting of crop productivity by cadmium (Cd) and lead (Pb), the potential transfer and bioaccumulation of these PTEs in plants, and ultimately the food chain contamination to ensure that the pre-established soil threshold concentrations for Cd and Pb are enough to control food chain exposure to them. Therefore, land cress and spinach were grown in some pots containing a sandy loam soil contaminated with increasing concentrations of Pb and Cd. The concentrations of Pb and Cd in land cress and spinach at any level of soil contamination were compared with the threshold concentrations of Pb and Cd in leafy vegetables as established by the Codex Alimentarius Commission (CAC). A bioaccumulation factor was calculated to estimate the potential transfer of Pb and Cd to the food chain. According to the results, Pb was of more phytotoxicity than Cd. The lower limit of the maximum acceptable concentration of Pb in soil was safe enough to ensure the prevention of the food chain contamination to Pb. Results also showed that growing land cress on contaminated soils was of great potential risk of Pb transfer to the human food chain when compared to spinach. The pre-established maximum acceptable concentration of Cd in soil of 1-20 mg kg-1 was not safe to prevent the contamination of food chain. Cd was of a greater potential of entering the human food.

Parameters that show a significant genotypic variation at early growth stages and are associated with salt tolerance at later stages may be used as rapid and economic screening criteria in breeding programs. The objective of this study was to test growth parameters at early growth stages for evaluating the salt tolerance of wheat genotypes. Ten wheat genotypes that differ from their salt tolerance were grown in soil and exposed to four salinity concentrations (0, 40, 80 and 160 mM NaCl). Germination percentage was recorded daily up to 8 days. Seedling growth parameters (i.e. shoot height, dry weight of shoots and roots and root/shoot ratio) were determined at day 14 after sowing. The results showed that salinity did not affect final germination percentage, while seeds subjected to 80 and 160 mM NaCl retarded germination by 1 and 2 days, respectively, as compared with 0 mM NaCl treatment. Salinity affected shoot growth more severely than root growth of seedlings. Importantly, height and dry weight of shoot ranked genotypes in the same order as their salt-tolerance rankings in terms of grain yield, whereas root dry weight did not. Therefore, we conclude that the measurements of shoot growth may be effective criteria for screening wheat genotypes for salt tolerance at early growth stages.

The objective of the paper was to illustrate using and usefulness of a joint AMMI and cluster analyses to assess the grain yield adaptive response of Polish and foreign 31 winter wheat cultivars in a range of 20 environments (locations) and across 3 years (2005-2007) under integrated crop management, using data obtained in the post-registration variety testing trials (called PDO trials), to identify those entries with specific and wide adaptation. Two-stage combined analysis of variance for data in the three-way GLY classification was carried out according to a mixed model (cultivar and location as fixed factors and years as random factor). GL repeated (across years) interaction effects were modeled by (a) joint regression and (b) additive main effects and multiplicative interaction (AMMI). The thirty one cultivar adaptive responses, expressed by nominal yields based on significant AMMI-1 model, accounting for 27.8% of SS for GL interactions, were divided into six homogenous groups by Ward’s method of cluster analysis. Group-mean cultivar adaptive responses indicated clearly the wide adaptation of cultivars in groups 1 and 2 including mostly German and United Kingdom entries and also two Polish ones. Cultivars from group 6, including three Polish cultivars and three foreign ones, were among at most four top-ranking entries at all locations excluding one environment (Wyczechy at Pomerania region). Cultivars from group 3, including seven Polish cultivars and one from United Kingdom and France, showed extremely specific adaptation characterized by nominal yield responses being positively related to GL interaction PC 1 scores of the locations. However, cultivars from group 5, including five Polish ones and a French one were poor adapted to the growing area. Presented the joint AMMI and cluster analyses were effective to distinguish adaptive responses of studied cultivars on the basis of data from PDO trials and could be seen as a better alternative, based more on probability-approached methodology, to common pattern analysis.

The influence of harvesting date on some physicochemical properties of nectarine (Prunus persica var. Red gold) fruit including fruit weight, pigment content, total carbohydrate, total phenol and antioxidant activity were studied. Fruits were harvested in four different stages; a) two weeks after fruit set, b) pit hardening, c) three weeks after pit hardening and 6 weeks after pit hardening. Results showed that the heaviest fruit either wet or dry was observed in the last harvesting date. The reduction in sucrose at the final harvest might be due to conversion to monosaccharides like fructose or glucose. On the other hand, although the content of total phenolic and flavonoid content of fruits were significantly reduced in the last harvest, no significant reduction was observed in their antioxidant activity. Generally, it can be concluded that compounds like anthocyanin, carotenoids and vitamin C play important role in antioxidant activity in ripened nectarine fruit and their content differ in different harvest times.