Iran Agricultural Research
Year:2005 | Volume:23-24 | Issue:1-2|Papers Count:8

Due to continuous flooding, irrigation management of rice (Oryza sativa L.) is very important, particularly in semiarid and arid regions where water is scarce. Rice plantation in I. R. Iran are located mainly in the humid; north, however, it is also grown in arid and semiarid areas of the country, including the Fars province, in the south. In this province, nearly 55000 ha of rice is grown under irrigated conditions. Therefore, research on proper irrigation management has significant impacts on crop and water use efficiency production. The present research was conducted in Kooshkak Agricultural Research Station of Shiraz University in 1997 and 1998 to determine lateral seepage, deep percolation, runoff, irrigation application efficiency and water use efficiency for irrigated rice. The cultivar used was a short season local cultivar, namely Champa-Kamfiroozi, commonly planted by most of the farmers in the studied area. For measuring deep percolation, a pair of cylindrical shape lysimeters, with a 56 cm diameter and a 100 cm height, were used in three locations in the rice field. In each pair, one of the lysimeters was bottom-less to allow for deep percolation. Thus, difference in water used in the two lysimeters was due to deep percolation. For measuring the inflow and outflow of water, 90 degree triangular weirs were used in the entrance and exit of the experimental plot, respectively. The difference between total water used in the field (measured by weirs) and actual evapotranspiration (measured by lysimeter) was considered as sum of lateral seepage and deep percolation. Subtraction of deep percolation from this sum showed lateral seepage. The amounts of daily deep percolation and lateral seepage were 3.4 mm and 0.19 m d-1  m-1 in 1997, respectively. These amounts were 3.5 mm and 0.22 m3d-1 m-1 in 1998, respectively. Surface  runoff which was the main source of water loss was 6.15 and 8.30 mm d-1 in 1997 and 1998, respectively. In order to investigate the effect of reusing surface runoff, application efficiency was calculated for both cases of runoff reuse and without reuse. In 1997, irrigation application efficiency with runoff reuse was 49.6% while its value was 30.8% without runoff reuse. For 1998, these values were 46.6 and 31.5%, respectively. The results showed an increase of 15% to 19% in irrigation application efficiency due to the consideration of runoff to be reused for the two years. Water use efficiency for rice grain was 2.9 and 2.5 kg mm-1 of water in 1997 and 1998, respectively.

One of the major problems with effective weed control is the presence of dormancy in weed seeds. In this study, the effects of stratification and scarification on seed germination and dormancy of Turgenia latifolia, Cuscuta sp and Sophora alopecuroides seeds in different temperature regimes were investigated. None of Turgenia latifolia hulled seeds germinated in any of the temperature regimes, whereas dehulled seeds germinated at 15 and 20°C. Also, scarification by acid sulfuric as a means of promoting germination significantly increased germination percentages of Cuscuta sp and Sophora alopecuroides seeds. Stratifying intact dormant seeds for 2,4,6, and 8wk increased germination rates dramatically. Best Turgenia latifolia seed germination was achieved with 8 wk stratification at 15 and 20°C (60 and 64%, respectively). Stratification did not stimulate the germination of Cuscuta seeds, whereas 8-wk stratification of Sophora alopecuroides seeds increased germination up to 40% regardless of the germination temperature. The results showed that both seed coat-imposed and internal dormancy were the main causes of Turgenia latifolia seed dormancy, whereas only seed coat-imposed dormancy was the main cause of Cuscuta sp and Sophora alopecuroides seeds.

An experiment was conducted on the F1 generation from a half-diallel set of crosses involving two drought tolerant (Roshan and Kal-Haydary), three moderately tolerant (Bayat, B.C Roshan and Nick-Nejad) and three sensitive (Ghods, Falat and Darab2) genotypes of wheat to study gene action of rate of water loss (RWL) from excised-leaf, initial water content (IWC), air-canopy temperature difference (DH=Ta- Tc) at booting and anthesis stages, and leaf water potential (LWP) and leaf osmotic potential (LOP) at the anthesis stage of development. Highly significant differences were observed between genotypes for all traits except for IWC (at booting) and DT (at booting and anthesis at 10-11 h). General combining ability (GCA) and specific combining ability (SCA) mean squares, and GCA/SCA ratios were significant for all traits, noting the importance of additive gene action. Non-additive gene action had a major role in DT at anthesis. Narrow sense heritability ranged from 46% for DT at anthesis to 72% for RWL at booting and anthesis stages. Heterosis was not important for any trait. The genotype Kal-Haydary was the best general combiner for all traits except for DT anthesis in which Roshan was better.

Pot experiment was carried out in greenhouse conditions to investigate the response of root yield and quality of sugar beet cultivars irrigated with saline water (tap water as control, 50 mM, 150 mM, 250 mM and 350 mM NaCl + CaCl2 in 5 to 1 molar ratio). Root yield decreased with increasing salinity. The low level of salinity decreased root yield of Madison and P29 cultivars by 25% and 36.1 %, respectively as compared to the control, while high level of salinity decreased root yield by 95.7% and 89.1 %. Root sucrose content of the two cultivars increased with increasing salt concentration up to 150 mM but further salt concentration, tended to decrease root sucrose content of cv Madison. Salinity significantly increased the concentration of a-amino-N and Na+ in the storage root. In contrast, potassium content tended to decrease at high levels of salt treatment. Salt stress increased unwanted sugars such as raffinose, glucose and fructose in the storage root. Although root impurity increased with increasing salinity, white sugar content (WSC) increased up to 150 mM salt treatment due to increasing sucrose content. However, higher salt concentration decreased the white sugar content of cv Madison because of the inverse effect of high levels of salinity on the sucrose content as well as greater molasses sugar. Cultivar P29 had greater white sugar content than Madison at high levels of salinity. The greater white sugar content in P29 at 150 mM and 250 mM was due to a greater root sugar content while at 50 mM salinity, it was because of lower molasses sugar. These results indicated that white sugar content increased at moderate salinity but white sugar content per plant drastically decreased because salinity had a greater effect on root yield than on white sugar content. Therefore, for saline lands, plant density per unit area should be considered.

A rapid and sensitive polymerase chain reaction (PCR) method is described for the determination of latent infections of Ralstonia solanacearum, the causal agent of bacterial wilt of solanaceous plants. The PCR tests with specific primers successfully detected R. solanacearum biovar 2 in all naturally and artificially infected potato samples with or without visible symptoms, and gave a characteristic 1019 bp band with division 2 specific DlV2F / DlV2R primers. As expected the PCR test with division I specific DIVIF / DIVIR primers did not produce any PCR product with any infected potato and tomato sample. None of the healthy control potato and tomato plants gave visible PCR products with the specific primers.

A total of fourteen dairy farms across the central province of Isfahan were visited for sampling wheat bran (WB) and beet pulp (BP) as the main commercial non-forage fiber sources fed to ruminants. Fiber fractions were determined using approved analytical procedures. Crude protein (CP) was fractionated into NPN (A), quickly degradable true CP (B1), moderately degradable CP (B2), slowly degradable CP (B3), and unavailable CP (C), based on the Cornell Net Carbohydrate and Protein Model. Descriptive statistics and correlation coefficients between fibers and CP fractions were calculated for all samples, and data for WB were analyzed in a completely randomized design. All fiber and CP fractions of WB except for C differed significantly across farms. The NPN, B3, and NDF were greater but CP, unavailable CP and B2 were lower in the WB of this study as compared to that of CNCPS feed library. The greater CP and lower fibers of BP used across Isfahan as compared to that of other reports were translated into more soluble fiber and thus more ruminally available energy in the samples of this study. The NPN, B1, and C in BP were significantly greater than the values found in the literature. Results indicated the necessity of a more dynamic evaluation of the nutrients in by-products if the diet formulation is to provide a more predictable animal response.

Dry land agriculture plays an important part in the agricultural production of the southern and western provinces of I. R. Iran. Since it utilizes precipitation directly, it is considered an optimal method of water use. The purpose of this research was to develop a simple model for the prediction of annual (water year) precipitation in southern and western provinces of I. R. Iran, so that dry land farming can be properly planned in these areas. The relationships between annual precipitation and the duration of 37.5, 42.5, and 47.5 mm of precipitation since the onset of autumn (t37.5, t42.5, and t 47.5) were analyzed using simple regression for all stations in the study areas. The results showed that 47.5 had higher correlation with the annual precipitation than t37.5 and t42.5. Furthermore, t47.5 was inversely related to the annual precipitation for all stations in the study areas. Among different parameters such as mean of annual precipitation, Pma (mm), elevation, longitude, and latitude of the stations, the mean of annual precipitation was the most appropriate one to be included in a linear multiple regression model along with t47.5 to estimate annual (water year) precipitation, Pa (mm) as follows:Southern provincesPa=-1.83 t47.5 + 0.76 Pma + 228.3,            R2=0.71 Western provinces Pa=-1.88 t47.5+ 0.94 Pma + 146.8,            R2=0.76 These models were validated by using data from the study areas not used for model development. The regression analysis showed a high correlation with a slope of approximately one between the predicted and observed values.