Research Article
Effects of Water Deficit and Potassium Humate on Tuber Yield and Yield Component of Potato Cultivars in Ardabil Region, Iran
Agricultural and Natural Resources Research Centre of Ardabil, P.O. Box 56491-11169, Ardabil, Iran
Water deficit is a common stress in potato production, which leads to yield and tuber quality decreasing. Because of potato susceptibility to drought (Hassanpanah et al., 2008), preparing sufficient water is very important for increasing potato quality and quantity. It is necessary to study about tolerance of different potato cultivars against water deficit stress and determination of potato water consumption in Ardabil, Iran. There is a water deficit problem in this region. Climatic changes occurred in this region at the recent years. These changes caused differences in precipitation dispersion, river flowing and wells water. Therefore, we have to identify agronomic characters and water need of new potato cultivars and more improvement of their quality and quantity.
Water deficit decreased number of leaves, plant water potentials (Frensch, 1997), leaf area, stem height, ground coverage, tuber number, growth and yield, canopy radiation interception and only to a lesser extent by effects on radiation use efficiency, harvest index and tuber dry matter concentration (Schittenhelma et al., 2006) and nitrate reductase (Misra et al., 2002) and increased reducing sugar content in the stem, tuber cracking and malformation, surface abrasions, hollow heart, brown center, internal brown spot, vascular discoloration or bruise, degradation of starch in the tuber stem end and total glycoalkaloids concentration (Papathanasiou et al., 1999). Reflectance indices were used to measure biomass and drought stress, changes in leaf water content (Francois and De Proft, 2005) and water stress (Bahrun et al., 2003). A set of drought tolerance genes previously found to be up-regulated in tolerant potato under drought (Schafleitner et al., 2007) was assayed for expression changes in potato under drought.
Potassium humate is a material with natural origin that extracts from plants and animal remains exist in the bottom of marshes. This material is formed from N, P, K and microelements namely Mo, Cu, Zn, B, Co, Mg (Gadimov et al., 2007). Using of potassium humate increased tuber yield about 11.01 t ha-1 under water stress condition (Hassanpanah et al., 2008), root number (Baraldi et al., 1991) and pea numbers and weight under saline stress condition and decreased nitrate amounts in leaves and roots (Gadimov et al., 2007) and decreased nitrate accumulation in potato tubers (Hassanpanah et al., 2007).
The objectives of this study were to interpret GxE interaction obtained of yield and yield component of potato cultivars and treatments of irrigation in three locations and two years, effects of water deficit and potassium humate on tuber yield and yield component of potato cultivars.
This experiment were conducted with three cultivars of potato [Agria (susceptible), Satina (semi-tolerant) and Caesar (tolerant to water deficit)] and four irrigation regimes (after 30 mm evaporation from basin class A; after 30 mm evaporation from basin class A with spraying by potassium humate; after 60 mm evaporation with spraying by potassium humate and after 60 mm evaporation from basin class A) for three locations of Ardabil (Alarog, Hassanbarog and Khoshkeroud) in Northwestern Iran, for two years (2007-2008). Experimental design was split plot design with two factors based on randomized complete blocks in three replications. Factor A was four irrigation regimes and factor B was three cultivars. Plot sizes were 9 m2 with four rows that each of them had 3 m length, 25 cm distance between plants and 75 cm distance between rows. Distances between plots were 1.5 m. The first irrigation was general, but the following irrigation time was determined as described above. Applied water amount was calculated according to the collected evaporation of A class basin every time and following equation:
IW/CPE = 0.8 |
Where:
IW | = | Irrigation water amount irrigation |
CPE | = | Collected evaporation ratio calculated from evaporation basin |
The amount of irrigation regimes water was measured by water meter. The start of irrigation was base on 30 mm evaporation from A class evaporation basin. Amount of precipitation was measured by udometer and daily evaporation by A class evaporation basin.
Potassium humate sprayed (250 mL ha-1) in the three stages of emergence, before tuberization and during tuberization period. In the growth period and after harvesting, the traits such as main stem number, plant height, tuber number and weight per plant, total and marketable tuber yield and dry matter percent were measured. The application of fertilizer was 350 kg N (Oreh) ha-1 at three stage (150 kg ha-1 at planting, 100 kg ha-1 at germination and 100 kg ha-1 at before tuberizatioin) and 150 kg P2O5 ha-1 at one stage (planting time). The harvested plot`s size was 3.75 m2 (two rows at the center of each plot having 2.5 m length). Combined analysis of variances were performed and comparison of means were done by LSD test. Correlation coefficients were calculated between different traits in irrigation regimes and potato cultivars in two years and three locations (2007-2008) by MSTATC software. Physical and chemical characteristics of soil and parameters of climatology of locations are showed in Table 1, 2.
Table 1: | Physical and chemical characteristics locations soil |
Table 2: | Parameters of climatology of locations (1998-2008) |
Table 3: | Analysis of variance of different traits on irrigation regimes and potato cultivars in three locations and two years |
+, *and **: Significant at 10, 5 and 1% level of probability, respectively |
Combined analysis of variance showed that were significant differences between year (Y), location (L), irrigation regimes (A) and cultivar (B) and their interaction (YxA, LxA, LxYxA, LxB and AxB) on total and marketable tuber yield, plant height, tuber weight per plant, interaction LxYxB and LxAxB on tuber yield, number of main stem and tuber weight per plant, interaction YxAxB on tuber yield, tuber weight per plant and dry matter percent (Table 3).
Table 4: | Mean of different traits in irrigation regimes |
Mean with the same letters in each column does not have significant difference at the 5% level of probability to according to value of LSD; Normal: After 30 mm evaporation from class A basin; Normal+Humate: After 30 mm evaporation from classabasin with spraying by potassium humate (250 mL ha-1) in the three stage of emergence, before tuberization and during tuberization period; Stress with Humate: After 60 mm evaporation with spraying by potassium humate (250 mL ha-1) in the three stage of emergence, before tuberization and during tuberization period; Stress: After 60 mm evaporation from classabasin |
Table 5: | Mean of different traits on potato cultivars |
Mean with the same letters in each column does not have significant difference at the 5% level of probability to according to value of LSD |
Table 6: | Mean of different traits on irrigation regimes for potato cultivars |
Mean with the same letters in each column does not have significant difference at the 5% level of probability to according to value of LSD |
The highest total and marketable tuber yield, plant height, number of main stem, number and weight of tubers per plant were produced in 2007. Result of decrease value of these traits was relative to decrease of amount of precipitation and increase of drought and heat stress on tuberization stage in 2008.
The traits of total and marketable tuber yield, plant height, tuber number and weight per plant had the lowest under stress conditions and the highest under normal and normal with spraying by potassium humate conditions and the trait of dry matter had the lowest under normal and normal with spraying by potassium humate and the highest under stress conditions. Spraying by potassium humate in water deficit condition increased tuber yield more than 0.93 and 9.63 t ha-1 under normal and stress conditions, respectively (Table 4). Hassanpanah et al. (2008) reported potassium humate increased tuber yield about 11.01 t ha-1 under water stress condition.
Caesar had the highest total and marketable tuber yield, plant height, tuber weight per plant and dry matter and Agria the lowest (Table 5).
The highest total and marketable tuber yield, plant height, tuber number and weight per plant and dry matter were produced in Caesar cultivar under normal with spraying by potassium humate, stress with spraying by potassium humate and stress conditions and Agria cultivar under normal condition (Table 6). Decreasing yield of Caesar under stress with spraying by potassium humate and stress conditions, relative to normal conditions (after 30 mm evaporation from basin class A) was 8.35 and 17.99 t ha-1 but for Satina was 15.66 and 25.1 and for Agria 6.79 and 16.58 t ha-1, respectively (Table 7).
Table 7: | Mean of tuber yield, increasing and decreasing of yield for potato cultivars |
Table 8: | Mean of different traits in three locations |
Mean with the same letter(s) in each column does not have significant difference at the 5% level of probability to according to value of LSD |
Table 9: | Linear correlation coefficients between different traits on potato cultivars and irrigation regimes |
*and **: Significant at probability levels of 5 and 1%, respectively |
Lynch and Tai (1989) showed genotypes were very sensitive to moisture stress at both tuber initiation and at the tuber sizing growth stages, the greatest variability amongst genotypes in response to stress occurred at tuber sizing.
Khoshkeroud and Alarog locations had the highest total and marketable tuber yield, plant height, tuber number and weight per plant and dry matter percent were produced toward Hassanbarog location (Table 8). Result of increase value of these traits was relative to increase of amount of precipitation (Table 2) and high quality soil (Table 1).
The total and marketable tuber yield, plant height and tuber weight per plant had high in 2007 year and tuber number per plant and dry matter percent under normal and normal with spraying by potassium humate conditions in 2008, in Khoshkeroud and Alarog locations, respectively and the lowest under stress condition in Hassanbarog location in 2008.
This study, dry matter percent of Agria cultivar were the highest than Satina and Caesar cultivars, therefore Agria cultivar is recommended for chips. Satina and Caesar cultivars had a lower dry matter, but are considered for fresh potato consumption (Table 5). Hassanpanah et al. (2006) reported Agria cultivar is recommended for chips and Satina and Caesar cultivars for fresh potato consumption.
If it is possible to prevent cold sweetening, they will loose less dry matter because of reduced respiration and it may even be possible to avoid the use of germination inhibitors. Lower sugars cause less wastage in chips production from dark chips (Hassanpanah et al., 2006).
There were significant and positive correlation between total tuber yield with marketable tuber yield, tuber weight per plant, main stem number and plant height and dry matter percent and marketable tuber yield with tuber number and weight per plant, main stem number, plant height and dry matter percent (Table 9). The results are according to Hassanpanah et al. (2008) report.
Total tuber yield and marketable tuber yield with main stem number had significant and positive correlation (Table 9). The main stem number per plant is one of the important traits for potato. As a general, if the stem number in potato becomes less, decrease tuber weight and finally tuber yield.
Marketable tuber yield with tuber number and weight per plant had significant and positive correlation. This means that although the tuber number has so effect on yield but this effect is by the tuber weight.
Comparison of irrigation regimes showed that spraying potassium humate under normal and stress condition induced increasing of tuber yield and yield components. Spraying by potassium humate in water deficit condition increased tuber yield about 0.93 and 9.63 t ha-1 under normal and stress conditions, respectively. Caesar had the highest tuber yield.