F. Salighehdar, Sh. Sedaghat-Hor, J. Olfati,
Volume 4, Issue 1 (3-2013)
Abstract
Aloe vera is a perennial liliaceous plant with succulent green leaves joined at the stem in a whorled pattern. It is highly appreciated due to its short growth period and high economic value among all the aloe species, and is used in pharmaceuticals, cosmetic products and food products. In order to improve Aloe vera cultivation in soilless culture, an experiment was conducted in 2011 in greenhouse of College of Agriculture, University of Guilan, Rasht, Iran, as a split plot bi-factorial in completely randomized design with four replications. Four nutrient solutions containing different levels of nitrate and potassium were the main plot, which were sampled at six different periods. Results revealed that the nutrient solutions affect measured traits after 5-6 months. In other words, in research programs for this plant, it is better to record the data for at least 5-6 months. In general, the nutrient solution containing 9.8 mM nitrate and 5.8 mM potassium lead to the best results in all sampling periods. In fact, Aloe vera plants respond positively to high levels of nutrients and in solutions containing the highest level of nitrate and potassium show the highest amount of measured traits.
F. Najafi Alishah, A. Golchin, M. Mohebi,
Volume 4, Issue 3 (10-2013)
Abstract
Lack of sufficient water resources and drought stress is one of the main problems for crop production in arid and semi-arid regions of the world, such as Iran. The use of water absorbing polymers (hydrogels) improves water retention capacity of soils and can lead to optimal use of the restricted water resources. In this research, the effects of four levels of Aquasorb water-absorbing polymer (0, 2, 4, and 8 grams Aquasorb per kg of soil) and three irrigation frequencies (3, 6 and 9 day intervals) on growth indices, yield and water use efficiency (WUE) of greenhouse cucumber, cultivar Negar, were investigated. The results showed that yield and growth indices of the cucumber were affected by the application of hydrogel and increased as compared with control. Also, water consumption by cucumber decreased significantly as the irrigation interval increased. The highest yield (196.3 g/plant) was obtained when the hydrogel was used at the rate of 2 g/kg of soil and irrigation interval was 6 days. Although the use of hydrogel increased water consumption of the cucumber, but its application at the rate of 2 g/kg soil significantly increased WUE (17.0 g/L) of this plant.
F. Lotfy, H. Sodaeizadeh, S. A. M. Mirmohammady Maibody, A. Mosleh Arani,
Volume 7, Issue 2 (8-2016)
Abstract
The ability of hydrogels to absorb large amounts of water implies that they both provide less soil water losses by preventing deep percolation of water and also increase water use efficiency of plants leading to decrease the effects of water deficiency due to salinity stress on crops. To study the effect of two types of superabsorbent (Stockosorb and Xanous) on growth of greenhouse cucumber under saline-soil conditions, a factorial experiment based on completely randomized design with 12 replications was carried out in Research Greenhouse of Yazd University. At the first stage of the experiment, effect of applying superabsorbent polymers (Stockosorb and Xanous) at three levels (0, 3 and 6 g/kg dry soil) was investigated 25 days after planting by measuring different characteristics including number of leaves, plant height, leaf length and leaf width. At the second stage, the abovementioned characteristics, along with the number of flowers and fresh and dry weight of plants, were measured 35 days after planting. Results indicated that at both stages, adding Stockosorb to the saline soil (EC= 5 dS/m) significantly increased all measured parameters when compared to the control. Application of two levels of Xanous hydrogel to the saline soil had no significant effect on measured traits, except on number of flowers, as compared to the control. Variations of number of flowers in both hydrogel treatments, and at both application levels, showed that using superabsorbent could be important in enhancing the crop yield under difficult saline conditions.
S. Mahmoudi, A. Mohammadkhani, V. Rouhi,
Volume 7, Issue 2 (8-2016)
Abstract
Aloe vera is one of the medicinal plants, resistant to drought and high temperatures, that its gel has many applications in pharmaceutical, health and food industry. This experiment was conducted to determine the effects of salinity stress, caused by sodium chloride (NaCl) and calcium chloride (CaCl2), on leaf weight, gel content and ratio of some nutrients in Aloe vera, in Research Greenhouse of Shahrekord University, in 2012. This experiment was based on a randomized complete blocks design with 16 treatments and three replications. Treatments included four levels of NaCl concentration (0 (control), 30, 60 and 90 mM), three levels of CaCl2 (5, 10, 20 mM) and combinations of the two salts Based on the results, effect of salinity on wet and dry weight of leaf and gel, percentage of sodium, calcium, magnesium, potassium, and K/Na and Ca/Na ratio was significant. Increasing the concentration of NaCL, CaCl2 or their combination, reduced the percentage of magnesium, calcium, potassium, wet and dry weight of gel content and leaf yield. Results of this study showed that Aloe vera is not much tolerant to salt stress and its cultivation is not recommended in soils with EC value of more than 7 dS/m. Overall, under similar EC, the toxicity of NaCl is more than CaCl2 and attention to potassium and calcium nutrition is important under salinity stress.
F. Salighehdar, A. R. Safari, A. Molaahmad Nalousi, S. Avestan,
Volume 7, Issue 2 (8-2016)
Abstract
Aloe vera is one of the most popular ornamental plants that is widely used in production of medicines and cosmetics. To investigate the effect of different ratios of peat and perlite on quantitative and qualitative characteristics of Aloe vera, a split-plot experiment, arranged as completely randomized design, with five substrates (peat, peat and perlite (1:3 v/v), peat and perlite (1:1 v/v), peat and perlite (3:1 v/v) and perlite, (main plots)) at five different times (sub-plots) was conducted. Results showed that adding perlite to peat substrate increased the growth rate and quantitative and qualitative indices of A. vera. Maximum amount of antioxidants, total phenols, aloin and dry weight of plants were observed in peat and perlite substrate (3:1 v/v). But, maximum number of leaves, plant height, number of shoots, root weight, leaf weight, total weight, gel weight and dry weight of leaves were observed in plants grown in peat and perlite substrate (1:1 v/v). Based on these results, the peat and perlite substrate (1:1 and 3:1 v/v) could be recommended to increase quantitative and qualitative indices of Aloe vera.
M. Rostampour, S. Zare,
Volume 14, Issue 4 (12-2023)
Abstract
Abstract
A review of research on soil and plant interactions in rangeland and desert ecosystems shows that the number of soil samples are not determined on a scientific basis. The present study, with the aim of using effect size and power analysis to determine the number of soil samples in three plant types of Salsola spp. was conducted in three arid and semiarid regions of Shahriar, Zirkouh and Zabol. In addition, 15, 10, and 5 soil samples were collected for each plant type, respectively. Some soil properties, including electrical conductivity, sand content, organic matter content, calcium carbonate equivalent, and saturation percentage, were determined in the laboratory. The number of samples was estimated after the initial sampling based on the calculated effect size (f) and the power of 80 % and before the sampling based on the medium effect size (f = 0.25) and the power of 60 %. The results showed that the power analysis of the three studied sites was 88, 56, and 38 %, respectively. To determine the minimum number of soil samples required to achieve a power of 80 %, at least 20 soil samples are required for Zabol and Zirkouh, and at least 12 soil samples are required for Shahriar. If there is no previous information about the soil properties, more than 50 soil samples must be collected from each plant type for a statistical comparison of three plant types with a medium effect size, a power of 80 %, and a significant level of 0.05.
Background and Objective: In the field of vegetation studies, there are statistical and graphical methods to estimate the number of plots needed for sampling, and their application has been approved in numerous research studies. In a review of research on soil and plant interactions in rangeland and desert ecosystems, it seems that the number of soil samples are not determined based on a scientific basis. Either by autecology or synecology, soil samples were taken from different depths at the first and end points of each transect according to the soil depth by using the random-systematic method (i.e., a total of 6–8 soil samples). The sampling scheme captures all the decisions and information, such as the purpose of the sampling, financial constraints, sampling method, sample size, method(s) of statistical analysis, and accuracy of results (Arzani and Abedi, 2015). One of the most frequent problems in statistical analysis is determining the appropriate sample size (Rostampour and Eftekhari, 2023). The present study has the aim of using effect size and power analysis to determine the number of soil samples in three plant types in the halophyte-psammophyte ecosystem of the arid and semi-arid regions.
Methods: The present study was conducted on three plant types of Salsola spp. in three arid and desert areas of Shahriar, Zirkouh, and Zabol. At Shahriar, Zirkouh and Zabol sites, 15, 10, and 5 soil samples were collected for each plant type, respectively. Then, the soil samples were passed through a 2-mm sieve and some soil properties, including electrical conductivity, organic matter content, sand content, calcium carbonate equivalent and saturation percentage were measured in the laboratory. In general, for estimating the number of samples based on power analysis, there is a need for three factors: effect size, power, and significant levels. In the present study, two methods were used to determine the number of soil samples: 1) the estimation of the optimal sample number after the initial sampling based on the calculated effect size (f) and the power of 80 %, and 2) the minimum number of samples before sampling based on the medium effect size (f = 0.25) and power of 60 %.
Results: The results showed that with an increase in the number of soil samples, the power analysis of the three studied sites was 38, 56, and 88 %, respectively. To determine the minimum number of soil samples required to achieve a power of 80 %, at least 20 soil samples are required for the Zabol and Zirkouh sites, and at least 12 soil samples are required for the Shahriar site. If the effect size is unknown due to the absence of data variance, the numbers of samples required for the sample sizes of small, medium, and large, and to reach a power of 60 % at the level of 0.05, are about 209, 35, and 14 samples, respectively. If there is no previous information about the soil properties, for a statistical comparison of three plant types with a medium effect size, a power of 80 %, and a significant level of 0.05, more than 50 soil samples must be collected from each plant type.
Conclusions: As per guideline, a power of 80 % is often considered an acceptable threshold, and studies with a power of less than 50 % should not be usually conducted. Accordingly, only the Shahriar site has a power above 60 %. Therefore, sampling from the Zirkouh and Zabol sites was not adequate for the statistical analysis. If there is no previous information about the soil properties, at least 50 soil samples should be collected from each plant type to compare the statistical significance of the three plant types with a medium effect size (F = 0.25) and a significant level of 0.05.
References:
1. Arzani, H., Abedi, M., 2015. Rangeland Assessment: Vegetation Measurement, University of Tehran Press, Tehran, Iran. (In Persian)
2. Rostampour, M., Eftekhari, A., 2023. Determining the sample size required to compare vegetation and soil characteristics in two independent groups using effect size in steppe rangelands of South Khorasan. Journal of Rangeland 16(4), 712–728. (In Persian with English abstract)
