JWSS - Journal of Water and Soil Science

---

In order to study the effects of rate and time of nitrogen application on vegetative characters, i.e., yield and yield components of rice (Zayandeh-rood variety), an experiment was conducted at Isfahan University of Technology research farm during summer 1996. Four N rates including (60, 90, 120 and 150 KgN/ha) and four splitting form (1- all N applied before transplanting 2- 1/3 N applied before transplanting, 1/3 at the beginning of tillering and 1/3 at the emergence of first panicle in 50% hills 3- 1/2 at the beginning of tillering and 1/2 at the emergence of first panicle in 50% hills 4- 1/3 at the beginning of tillering and 2/3 at the emergence of first panicle in 50% hills) were evaluated in a factorial experiment which was arranged in a randomized complete block design with 3 replications. Plant height, number of tillers per unit area and days to heading and maturity increased with an increase in the rate of fertilizer application. Grain yield and number of panicles per square meter increased when the N rate was raised to 120 Kg N/ha, while application of 150 Kg N/ha resulted in the reduction of grain yield and number of panicles. Nitrogen rate increases did not have any significant effect on number of grains per panicle. The grain weight did not follow any particular trend at different application rates, but harvest index and percentage of filled grains were decreased as the N rate increased. The percentage of nitrogen content of plant was increased as a result of higher N - rate at heading and harvest times. Treatments containing base application of nitrogen resulted in an increase in plant height, number of tillers, plant dry matter, grain yield and number of panicles per square meter, although it caused a reduction in harvest index. The number of grains per panicle and grain weight did not follow any particular trend under the influence of time of application, although plant nitrogen content increased with a delay in time of fertilizer application.

---

The purpose of this research is to determine the application efficiency of rice irrigation plots and to analyze the reasons for low efficiency. The study will also try to determine the effective factors which could increase the application efficiency of rice fields. The selection of rice fields was based on climate, soil characteristics, and farmer management. Water application efficiency was determined by field measurements in three modern irrigation networks named Fouman (F), Rasht (G) and Lahidjan (D). In the meantime, a traditional network was included for comparison. In the study areas, the soil texture was heavy with an infiltration rate of less than 3 mm/day. The study was carried out under two different conditions: (1) without return flow and (2) with return flow. In the first case, the average application efficiencies in Fouman (F), Rasht (G) and Lahidjan (D) were about 51.2, 49.0 and 49.4 percent, respectively and the maximum and minimum values were about ((52.6, 49.7)), ((50.7 , 47.3)), and ((50.7 , 48.0)) percent, respectively. In the second case, the average application efficiencies for the above-mentioned regions increased to 73.4, 73.3 and 72.4 percent, respectively and the maximum and minimum values were about ((74.3, 72.4)), ((74.3, 72.1)), and ((73.0, 71.5)) percent, respectively. Runoff ratios in the above-mentioned regions were 30, 33 and 31 percent, respectively. During growing period (from transplanting to harvesting), the average applied irrigation water was about 1130 mm (11300 m³/ha) and the average evapotranspiration was determined to he about 561mm.

---

High-yielding rice varieties are prevailing in Guilan Province which is one of the most important rice producing regions in Iran. However, little is known about K status in this region and no suitable extraction method can yet be introduced to the farmers. This experiment was carried out to determine the available K by 15 chemical extractants and also to examine the critical K levels in paddy soils of the region. The treatments included 23 soils and 2 K levels (0 and 300 mg/kg as KCl) in a factorial experiment in a randomized complete block design with three replications.

 Results indicated that K application increased grain and straw yields, K concentration in straw as well as K uptake by rice. High correlation coefficients were observed between MgOAc, H₂SO₄, Morgan and 0.01 M CaC_l2 methods with K concentration in straw (0, 0.83, 0.78, 0.8 and 0.78, respectively) and with K concentration in plant tops (0.79, 0.76, 0.75 and 0.73, respectively). Similarly, high correlation coefficients were observed between the same extraction methods with K absorbed by straw (0.83, 0.82, 0.78 and 0.76, respectively) and with total plant K uptake (0.79, 0.83, 0.74 and 0.71, respectively). Potassium critical levels by different extracting solutions were determined by Cate-Nelson procedure and were 38, 74, 160, 111, 36, 112 and 100 mg kg^-1 for MgOAc, Morgan and Kelowana methods, Texas method H₂SO₄ 0.01 M CaCl₂ and NH₄OAc without and with submergence of soil samples, respectively. In this study, available K was below the critical level in almost 75% of the soils.

---

This study was conducted to evaluate the response of 18 rice (Oryza sativa L.) genotypes to callus induction and plant regeneration from immature embryo culture, using three media (MS, LS and N6). To evaluate callus induction rate, the following criteria were used: callus diameter, callus fresh weight and callus dry weight. Percentage of callus water content was also measured. After transferring the produced calli from the induction media to a regeneration medium (MSR), percentage of plant regeneration was evaluated.

A highly significant difference was observed among genotypes for both callus induction and plant regeneration (P<0.01). In callus induction phase, “Nemat” and “Cheram-2” cultivars were superior for callus diameter, having 4.83 and 4.6 mm callus diameter, respectively. “Nemat”, “Cheram-2”, “Sepidrood” and “Taroum” cultivars as well as “33IRCTN91” and “IRFAON-30” lines were significantly superior to other cultivars for callus fresh weight. Among the genotypes “Nemat”, “Zayandehrood”, “33IRCTN91” had the highest percentage of callus water contents. Based on plant regeneration, “33IRCTN91” line and “Anbarbo”, “Nemat”, “Cheram-2” and “Taroum” cultivars showed highest rate of plant regeneration from callus. Significant differences were observed among media. While MS and N6 media did not showed any significant differences for callus diameter, callus fresh weight and rate of plant regeneration, they were superior to LS medium (P<0.01). According to percentage of callus water content, MS and LS media ranked the best and the most inferior medium, respectively. In the present study, MS and N6 media were considered as suitable in vitro culture media of rice immature embryos. Among genotypes, “Nemat” and “Cheram-2” cultivars were ranked the best for both callus induction and plant regeneration. Also, the used Japonica rice cultivars were superior for percentage of plant regeneration. The calculated correlation coefficients between traits showed a non-significant correlation between callus induction and plant regeneration, which, in turn, indicated that these traits were independent.

---

During recent years, worldwide concern has been focused on the potential for contamination of surface waters and ground waters by agrochemicals in runoff and soil water from irrigated fields. Given this perspective, it is very important to correctly evaluate the levels of different agrochemicals in water, both from human toxicological and environmental viewpoints and to develop management strategies for reducing agrochemical loads to acceptable levels in the environment. The main objective of this study was to assess the qualitative changes of tailwater due to the use of agrochemicals and thereby to determine contamination loads. Four farms (A, B, C and D) were chosen in the Foumanat region in the F₂ unit in 1996. The areas of these fields ranged from 0.22 to 0.6 ha having a number of unequal successive basins with variable inflow and outflow rates.

 A quantitative analysis showed that the tailwater ratio in farms A, B, C and D ranged from 2 to 64% during the irrigation season. The outflow water was classified as C₃S₁. The changes in qualitative factors were not significant and did not follow any certain pattern during the irrigation season. The changes in SAR, EC, Cu, Zn, B, P, K and DO in the inflow and outflow waters were also insignificant. After fertilizer application, the increase in nitrogen concentration in the outflow was significant. The average pollution loads in the inflow and outflow were about 1618 and 1476 kg/day/ha, respectively. The remaining load in the rice fields was about 142 kg/day/ha, which was meaningful at 1% level. The fifth farm (E) located in Lahidjan was sprayed with diazinon. Water samples were analyzed each day for diazinon residues for 10 days after application. Sample analysis showed that the concentration of the insecticide was 93.08 mg/l immediately after application and gradually reduced to 0.98 mg/l ten days after spraying.

---

In order to study the parasitoid flies of Sunn pest in Isfahan, this research was conducted during the years 1997-1998. The results indicated that the dominant species of parasitoid fly is Phasia subcoleoptrata L. This species has two generations per year and over winters as pupae in soil under the shrubs of aestivation and hibernation places of Sunn pest and remains there until the following spring. The adults of the first generation of this parasitoid emerge from the pupae before the Sunn pest migrate to the grain fields and parasitize on the Sunn pest at the time of migration. About 6-8 days after the flies lay eggs in the body of Sunn pests, parasitoid larvae hatch from the eggs and grow in the body of their host. Larval period of parasitoid lasts about 15-20 days and then they fall on to the soil and pupate. In the laboratory, the length of pupal period for males and females is 17 and 18.5 days, respectively, for the first generation. Flies of the second generation of the parasitoid parasitize the fifth nymphal instar and the new adults of the Sunn pest.

---

Rice bran is the most important by-product of rice milling. It is a valuable source of edible oil in most rice producing countries. Rice bran oil is used in babyfood, biscuit, poultry, fish and farm animal feeds. The storage of rice bran without 'heat processing will result in hydrolysis and auto-oxidation of lipids, and to its decreased physicochemical, organoleptic and nutritional quality. Rice bran is rich in carbohydrates, free amino acids, lipids and different enzymes. The enzymes have destructive effects on the quality of rice bran components. Heat processing is an effective method to reduce the microbial and enzymatic activity of bran.

This study was carried out using a factorial experiment by completely randomized design with three replications to investigate the effect of heat treatment and storage time on rice bran crude oil properties. The parboiling treatment was effective on the rice kernel strength. The bran produced from parboiled rice milling had lower endosperm components. This type of bran had a lower starch but a higher oil percentage. The results of color of rice bran oil samples determined by Lovibond showed that the oil from parboiled rice bran before and during storage had better color than the other samples. Iodine value of bran oil from parboiled paddy decreased during the storage period. The results from studies on fatty acid composition of oil samples determined by gas chromatography (G.C.) showed that the quantitative trend of fatty acids of the control sample remained the same as that in the rice bran samples with the treatment process.

---

Rice bran is the most important by-product of rice milling. It is a valuable source of edible oil in most rice producing countries. Rice bran oil is used in babyfood, biscuit, poultry, fish and farm animal feeds. The storage of rice bran without 'heat processing will result in hydrolysis and auto-oxidation of lipids, and to its decreased physicochemical, organoleptic and nutritional quality. Rice bran is rich in carbohydrates, free amino acids, lipids and different enzymes. The enzymes have destructive effects on the quality of rice bran components. Heat processing is an effective method to reduce the microbial and enzymatic activity of bran. This study was carried out using a factorial experiment by completely randomized design with three replications to investigate the effect of heat treatment and storage time on rice bran crude oil properties.

The parboiling treatment was effective on the rice kernel strength. The bran produced from parboiled rice milling had lower endosperm components. This type of bran had a lower starch but a higher oil percentage. The results of color of rice bran oil samples determined by Lovibond showed that the oil from parboiled rice bran before and during storage had better color than the other samples. Iodine value of bran oil from parboiled paddy decreased during the storage period. The results from studies on fatty acid composition of oil samples determined by gas chromatography (G.C.) showed that the quantitative trend of fatty acids of the control sample remained the same as that in the rice bran samples with the treatment process.

---

In order to investigate the best planting time and rice cultivars for the conditions in Khuzestan Province, seven high quality cultivars of rice namely Domsiah, Binam, Ramasanali Tarom, Sang Tarom, Hasansarai, Tarom Mahalli, Daylamani and Anboori were selected and studied in 4 planting dates starting in Mid-May, with intervals of 15 days. The experiment was conducted as a split plot design in randomized complete blocks with 3 replications for 2 years from 1995 in Shavoor Agricultural Research Station. Main plots were planting dates and subplots were allocated to cultivars.

Results of this experiment showed that significant differences existed among planting dates on grain yield only in the second year. Grain yields were different among cultivars in the two years of study. Simple and combined analyses indicated that there were significant interactive effects between planting dates and cultivars. Tiller number was different between planting date and cultivars in the first year. Interactive effect between planting date and cultivars on tiller number was not significant. Maximum grain number in spike obtained early June planting date (76 grains per spike) and lowest grain number in spike obtained early May planting date (28 grains). Among cultivars, Anboori with 152 and Daylamani with 17 grains had maximum and minimum grain numbers in spike, respectively. One-thousand grain weight was maximum in the early June planting date. Among cultivars, Binam and Daylamani had maximum and minimum grain weights, respectively. Highest fertility percentage was obtained in early June planting date compared to other planting dates. Fertility percentage of cultivars depended on temperature at growth stages before and at anthesis, which was early June for all cultivars. Among environmental factors affecting plant growth, temperature was relatively more important than other factors, particularly than the photoperiod. Even under Khuzestan conditions, there is a wide range of temperature levels for rice planting (from early March to early November) however, even this wide temperature range may not be enough to provide favourable conditions for planting all the cultivars.

---

This paper studies the structure of cost and production of rice using cross section data from rice farming in Guilan in 1997. A translog cost function is specified for this purpose and estimated, using Iterative Seemingly Unrelated Regressions for both the short and the long run where all factors are taken to be variables. The results of the study are as follows:

1. Neither in the short-run nor in the long-run is the possibility of technical substitution among the factors of production strong.

2. Own and cross price elasticity of demand for inputs are positive but less than one, hence limited substitutability among inputs is possible as the result of a change in input prices.

3. As the structure of production of rice in Guilan exhibits increasing returns to scale, increased allocation of land to the production of rice could result in a lower price of the product.

4. Inputs are not homogeneous, therefore, not all producers are faced with the same price for the same input. Nevertheless, the cost of production has been lower for those farmers who have paid a higher price for an input. Therefore, the higher price for inputs is more than that compensated by the quality of each input in the production process.

5. Due to the inelasticity of the demand for rice with respect to prices, a large price increase is required to stimulate farmers to allocate more resources to the production of rice.

6. Since the possibility of substitution among inputs is limited, a large increase in relative prices is required in order to change the structure of rice production.

---

This research was conducted in Kooshkak Farm Research Station of Shiraz University in 1997 and 1998 in order to determine crop coefficient and water requirements of rice, using lysimeter. The variety used was Champa-Kamfiroozi which is an early mature variety and is grown by most farmers in the area. Results showed that potential evapotranspiration varied from 3.76 to 9.34 mm/day. Penman FAO method was used in calculating reference evapotranspiration. Crop coefficient was 0.97 in the initial growth stage, 1.25 in the mid-season growth stage, and 1.09 at the time of harvest. Total crop evapotranspiration rates in 1996 and 1997 were 560 and 757 mm, respectively. Average deep percolation rates in the growing season was 3.4 and 3.5 mm/day in 1996 and 1997, respectively. Finally the total water requirements of rice in 1996 and 1997 were 1983 and 2361 mm, respectively.

---

Antagonistic fungi Trichoderma harzianum (T₁, from bean fields in Ahwaz, T₂, from rice fields in Rasht), T. viride (T₃ from bean fields in Shahriar, T₄ from the collection in Plant Pest and Disease Institute, Tehran), Gliocladium virens (from bean fields in Kamal Abad, Karaj) and some fungicides (Benomyl, Carbendazim, Carboxin-Thiram, edifenphos and Zineb) were used to control sheath blight of rice incited by Rhizoctonia solani in vitro and under greenhouse conditions. The experiment was carried out in a completely randomized design with 12 treatments and four replications on Khazar rice cultivar in a soil infected by R. solani under greenhouse conditions. The results showed that the antagonistic fungi reduce sheath blight by 19.8 (T₁), 21.5 (T₂), 27.5 (T₃), 19.6 (T₄) and 18.5 (G₁) percent. The antagonistic fungi in order of efficacy were T₂>T₃>T₁>T₄>G₁. Benomyl, Carbendazim, Carboxin-thiram, Edifenphos and Zineb reduced disease by 32.5, 21.5, 12.8, 9.5 and 0 percent, respectively. Statistical analysis of data indicated that there existed no significant differences between T₁, T₃, T₄, and G₁ and Carbendazim fungicide to control disease however, the isolate T₂ was as effective as Benomyl but Zineb had no effect on sheath blight.

---

In this study, the effect of deficit irrigation with every–other furrow irrigation method, which is an innovated method in farm irrigation management, was examined on sorghum (Sorghum durra L.) in Bajgah and Kooshkak areas of Fars Province. The experimental design was split plot with three main plots of irrigation interval (10, 15 and 20 days), three subplots of irrigation methods (ordinary furrow, fixed and variable every–other furrow), and 4 replications. Considering the crop production cost with real and subsidized prices of water in both areas, the net benefit per unit volume of irrigation water and benefit–cost ratio were calculated. The results showed that these economic parameters for the fixed and alternative furrow irrigation methods of 10-day intervals in both areas did not differ much with those of the ordinary furrow irrigation with 10-day intervals and were even higher in Bajgah area. Furthermore, the relationship between the amount of irrigation water, water application efficiency (Ea), water price per unit volume (Cw) and the net benefit per unit volume of irrigation water (B) with different conveyance efficiencies (Ec) were determined by multiple linear regression procedure. The regression coefficients of linear fit equation between the costs and irrigation water were determined. The results indicated that with higher price of water, the farmer should increase the farm irrigation application efficiency to avoid the economic losses.

---

Rice husk, an agricultural waste, is produced about 100 million tons annually in the world and 0.5 million tons in Iran. Due to growing environmental concerns about disposal of these wastes, efforts are required to apply the wastes in industry. In this research, the mechanical properties of concrete incorporating rice husk ash (RHA) in sulfate environments (such as irrigation canals) were investigated and the increase in concrete strength was compared with control samples. In order to burn the husks at a controlled temperature to obtain a highly reactive pozzolanic RHA, a furnace was designed and built. The experiments included 405 samples of cubical (707070-mm) and cylindrical (50.8101.6-mm) concrete samples (105 samples for A, B and C treatments, respectively) which were stored in different ages (7, 28, 60, 180 days) under three different conditions (solutions of magnesium, calcium and sodium sulfates). The portions of RHA as cement replacement were 20 and 30 percents for B and C treatments. The results showed that the samples of concrete containing 20 percent RHA as cement replacement had higher compressive and tensile strengths in sulfate environments at 180 days compared with those of control concretes. The concrete samples containing RHA showed sharper gradients compared to control samples of up to 180 days under sulfate conditions. The best portion of RHA in concrete was determined to be 20 percent by weight.

---

To study the genetic diversity in 100 genotypes of rice, an experiment was conducted at the research farm of Rice Research Institute of Iran. The experimental design was a 10x10 simple lattice. The genotypes, mostly belonging to Isfahan Province and north of Iran, were evaluated on the basis of morphological traits and yield components. The results of analysis of variance demonstrated that the differences among genotypes were highly significant (p < 0/01) for all traits. High values of phenotypic and genotypic coefficients of variation were obtained for most traits, indicating high variability in the traits under study. Factor analysis revealed three factors which determined 90 percent of yeild variation and were named “grain number”, “plant type and structure” and “grain shape”, respectively. Cluster analysis by “Cubic Clustering Criterion” and “Pseudo Hotelling T² Test” grouped genotypes in four clusters. Analysis of variance showed that the differences among clusters were highly significant for most traits.

---

Traditional paddy dryer systems in Iran cause considerable losses in rice production due to non-uniform drying. In order to decrease the amount of kernel fissuring and to increase the drying rate, fluidized bed method was applied in this study for rough rice drying at temperatures higher than normal. An experimental dryer was used for drying the samples. The drying experiments were set up to find kernel fissuring percentage and the drying times under three conditions: fixed, minimum, and full fluidized bed conditions at temperatures of 40, 60 and 80^oC. Results showed that the amount of kernel fissuring, at minimum fluidization compared to fixed bed condition, decreased 57%, 68% and 75% at temperatures of 40, 60 and 80^oC, respectively. This reduction at full fluidization compared to fixed bed condition, at the above temperatures, was 40%, 54% and 65%. The minimum fluidization method took the lowest and the fixed bed method took the highest drying time. It was concluded that the minimum fluidization drying method had the lowest fissuring and drying times at all experimental temperatures.

---

Systemic properties of pyroquilon, an anti-blast systemic chemical, used in controlling rice blast disease caused by Pyricularica grisea, was investigated through in vivo tests. Rice plants were treated with pyroquilon as granules in soil. Leaf and stem tissues were collected at different times after treatment and pyroquilon was extracted from tissues and detected by gas chromatography. Treated rice plants were also exposed to disease infection in blast nursery at different times and disease incidence was evaluated one week later. Pyroquilon was detected in leaf tissue one day after treatment (DAT), reached maximum during 4-7 DAT, and then reduced gradually to a nondetectable level after 28 DAT. In stem tissue, change in pyroquilon content was similar to but its quantity was less than that of leaf tissue. On inoculated plants, disease was controlled up to 60% at 2 DAT and completely controlled during 4-28 DAT. The results indicated that pyroquilon could be taken up and systemically translocated in rice plants after applying as granules in soil. Extent of disease control was a good function of pyroquilon content in leaf tissue (R²=0.93) and 2 ppm of compound in leaf could provide 90% control of the disease. In contrast, disease control was not a good function of pyroquilon content in stem tissue (R²=0.30).

---

One hundred and two microorganisms were isolated from 85 paddy soil samples of different locations in Guilan Province. Antagonistic effects of the microorganisms were tested against Gibberella fujikuroi on PDA medium. Twenty one microorganism isolates were selected for seed treatment in blotter test. Seven isolates that were satisfactorily effective in reducing pathogen colonies formed on seeds and seedlings were tested in controlling disease in a greenhouse experiment with split plot design. The antagonists were Bacillus subtilis, B. circulans, Bacillus sp., Trichoderma harzianum, T. virens (2 isolates), and F.23 (unidentified). Results showed that all antagonists effectively reduced the disease in sterilized soil compared with control but overall effectiveness of B. subtilis, T. harzianum, and T. virens was higher than others and lower than the fungicide treatment (thiophant methyl thiram W.P. 80% , 2g/L). It was found that when seeds were treated with antagonists prior to inoculation with the pathogen, the effectiveness of antagonists was significantly better than when they were applied after seed infection with the pathogen.

---

A major limitation for higher yield of rice plant is water availability. Water use efficient varieties tolerant to upland conditions could help to relax this limitation. Three separate experiments were conducted to study the effects of water regimes on growth, aerenchyma formation, and nutrient absorption of Iranian rice varieties. In the first experiment, five varieties of rice were grown under three different irrigation levels. The second experiment involved the study of nutrient uptake by Sazandagee and Tarom varieties under four different water regimes, and in the third experiment, the effect of aeration on growth characteristics of Sazandagee rice was assessed in a hydroponics system. Results of the first experiment showed that submerged conditions continuously or after four weeks of initial growth had a significant effect on plant growth. Aerenchyma formation was affected by rice varieties and was less affected by irrigation status. In the second experiment, plant growth characteristics were affected similar to experiment one. Also it was shown that nutrients such as P, Mg, and Fe were absorbed with higher efficiency under submerged conditions. Results of the third experiment revealed that aeration had no significant effect on plant growth characteristics. Based on the results of these three experiments, it can be concluded that better performance of rice plant under continuous or partial flooding is mainly related to higher absorption of some macro - and micronutrients. Therefore, this parameter should be considered in water management programs for rice.

---

The egg parasitoids are the major natural enemies of sunn pest and application of selective insecticides is one of the strategies for conservation of natural enemies. The toxicity of five different insecticides used in cereal fields to the parasitized eggs was investigated under laboratory conditions. The insecticide solutions were made based on the recommended field rates. 3-, 5- and 8- day -old parasitized eggs were dipped into insecticide solutions. Among the treated developmental stages (except for the fenirothion), 3- and 8- day- old parasitized eggs showed the highest and the lowest emergence percentages, respectively. Deltamethrin had maximum effect on emergence percentage whereas phosalone had the least hazardous effects. There was a significant difference in parasitism percentage between 3- and 8- day- old parasitized eggs in each of the 4 treatments, viz trichlorphon, fenitrothion, deltamethrin and esfenvalerate. Adults emerging from 3- day- old eggs parasitised less eggs than those emerged from 8- day- old eggs in fenitrothion, and trichlorphon treatments. All tested insecticides were highly toxic to the adult parasitoid, causing 100% mortality when the adults were exposed to sprayed areas at recommended rates.