فهرست مطالب a. aien

This study with the aim of determining the effect of deficit irrigation and mulching on watermelon was conducted with a preliminary experiment in the form of split plots and a design of complete randomized blocks with three replications, in the Research and Education Center of Agriculture and Natural Resources in the south of Kerman province (Jiroft), in 2021‒2022. Drip irrigation as the main plot at three levels of 100, 70 and 50% of water requirement and mulching in three levels of crushed date palm leaf, black plastic and no mulch, as the sub-plot, were considered. As results demonstrate, the main and interaction effects of the treatments on stem length, leaf area, yield, water productivity, leaf relative water content, photosynthetic pigments, proline, total phenol, leaf superoxide dismutase enzyme and fruit length and width were significant. The main effects of irrigation and mulching on internode length, membrane stability index and vitamin C, and the main effect of the irrigation on the percentage of fruit dry matter, stem branches, and the main effect of mulching on fruit shape and soluble solids were significant. Fruit pH and total acidity, tasting and lycopene were not significantly affected by the treatments. The highest yield (60.1 ton/ha) was observed in the full irrigation and plastic mulch, and the highest water productivity (15.1 kg/m3) was recorded in the 70% irrigation and plastic mulch, but no significant difference with full irrigation and plastic and date palm leaves mulches. The findings showed that the effectiveness of plastic mulch on the watermelon growth and yield was higher with 100% and 70% irrigation compared to 50% irrigation. The date palm leaf mulch, despite being superior to the control in the full irrigation, had insignificant positive effects in deficit irrigation levels due to its high sodium content (1800 mg/kg).

Deficit irrigation has been mentioned as one of the effective techniques for increasing the water productivity of plants. Deficit irrigation of 50% caused a decrease in yield and water productivity of watermelon in Valencia region of Spain (Abdelkhalik et al., 2019). The role of mulching in compensating the negative effects of deficit irrigation has been confirmed in the literature (Diaz-Perez, 2023). This research aims at investigating the effects of deficit irrigation and mulching on the growth, yield and fruit quality of watermelon and the possibility of replacing plastic mulch with date palm leaf mulch.

Irrigation as the main plot at three levels of 100, 70 and 50% of water requirement and mulching at three levels of crushed date palm leaf, black plastic and no mulch, as the sub-plot, were considered. Crimson B 34 watermelon seeds produced by Seminis company, were planted on January 2021, in plots with the size of 13.5 × 7 m, on furrows and ridges planting system (the width of furrows and ridges were 0.5 and 4 meters, respectively). After planting, bow-shaped wires were put on the planting rows and a transparent plastic was placed as a tunnel on them.

Analysis of variance of the plant growth, yield, water productivity, and some physiological and biological traits displayed that the main and interaction effects of treatments were significant. Some traits such as pH, titratable acidity, fruit taste and shape were not affected by the treatments. The main and interaction effects of the treatments on stem length, leaf area, yield, water productivity, leaf relative water content, photosynthetic pigments, proline, total phenol, leaf superoxide dismutase enzyme and fruit length and width were significant. The main effects of irrigation and mulching on internode length, membrane stability index and vitamin C, and the main effect of the irrigation on the percentage of fruit dry matter, stem branches, and the main effect of mulching on fruit shape and soluble solids were significant. Fruit pH and total acidity, tasting and lycopene were not significantly affected by the treatments. The highest yield (60.1 ton/ha) was observed in the full irrigation and plastic mulch, and the highest water productivity (15.1 kg/m3) was recorded in the 70% irrigation and plastic mulch, but no significant difference with full irrigation and plastic and date palm leaves mulches was obtained. Reducing the irrigation water from 100 to 70 and to 50% of crop evapotranspiration or ETc (estimated by the FAO-Penman-Monteith method) in all three types of the mulch led to a significant decreasing in yield (Y), which was caused by the occurrence of water stress. The first reduction in water use (i.e., from 100 to 70%) increased the water productivity (WP) even though not significantly, but the second reduction in water use (i.e., from 70 to 50%) significantly led to a decrease in WP.

Overall, the 100%ETc treatment with black plastic mulch will probably have the best result in terms of watermelon yield unless water shortage, water price, and irrigation cost are noticeable compared to the crop price. In this case, 70%ETc irrigation with black plastic will be a priority in terms of WP. Of course, the cost of mulching and its possible environmental consequences should be considered.

Intercropping system is the growth of two or more crops at the same time, which can lead to decreases in the risk of total crop reduction and increases in yield with control of weeds. Quinoa (Chenopodium quinoa willd.) is a pseudo cereal with high nutritional value which is approximately a new crop in Iran. So, this research was conducted to assess the effects of additive intercropping of quinoa andpotato (Solanum tubersum L.), and the methods of weeds control on yield and yield components of quinoa var. Titicaca in Jiroft and Kahnooj regions.

This study was carried out as split plot based on a randomized complete block design (RCBD) with four replications at Jiroft and Kahnooj regions. Therefore, weeds control treatments including control (no-hoeing), manual weeding (twice within 30 days after planting) and paraquat herbicide (3 days after planting of quinoa) were arranged in the main plots, while additive intercropping patterns at five levels (Q:P in the levels of 5:5, 10:5, 15:5, 20:5 and 30:5 plants per m-2), quinoa sole cropping (30 plants per m-2) and potato sole cropping (5 plants per m-2) were located in sub-plots. The effects of quinoa and potato intercropping on plant height, leaves number per plant, leaf area, flowering time, spike maturity and quinoa harvest time, average of grain weight per plant, grain yield and density of weeds as well as potato tuber yield were measured at both regions. Data were analyzed as combined analysis of variance (ANOVA) using SAS ver. 9.2. Means were compared using the least significant difference (LSD) at the 5% level (P = 0.05).

The results showed that the effects of quinoa and potato intercropping had significant effects on some characteristics of quinoa including leaves number per plant, leaf area, average of grain weight per plant, grain yield of quinoa, tuber yield of potato and density of weeds. However, intercropping had no effect on some characteristics of quinoa such as plant height, flowering time, spike maturity and quinoa harvest time. Based on the results the highest (19 g per plant) and lowest (13.9 g per plant) average of grain weight per plant were obtained in 20:5 and 5:5 plants per m-2 treatments, respectively. Whereas, the highest grain yield (4957 and 4863 kg.ha-1) were obtained in sole quinoa and 30:5 plants per m-2 treatments, respectively. The studied growth characteristics and grain rate per plant in Kahnooj were greater than those in Jiroft. Total land equivalent ratio (LER) index increased with increasing quinoa density in intercropping. The highest total LER was obtained in 30:5 plants per m-2 treatment in Kahnooj region. Moreover, the effect of manual weeding of weeds on the studied properties were more than that of the application of paraquat herbicide. The results also showed that the intercropping of quinoa and potato led to decreases in density of weeds at both flowering and before harvesting times. So that, the lowest density of weeds was related to the intercropping of quinoa and potato with densities of 20:5 and 30:5 plants per m-2 treatments. Whereas the highest rate of density of weeds were related to the sole cropping of quinoa and potato treatments, respectively. Moreover, the results showed that intercropping resulted in greater tuber yield of potato, so that the highest potato tuber yield was obtained in 30:5 treatments.

Based on the results, although the highest average grains per plantwas obtained in the intercropping of 20:5 treatment, the yield of quinoa decreased with the intercropping of quinoa and potato compared with the quinoa sole cropping. Also, the additive intercropping led to decrease in the density of weeds. Although, it seems that for quinoa cropping the climate of Kahnooj is more suitable than Jiroft, the intercropping of potato and quinoa is suitable for Kahnooj and Jiroft regions.