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The unmanned aerial vehicles (UAVs) are widely used for agricultural monitoring due to reduce the cost and time of crop monitoring via the acquisition of images with high spatial-temporal resolution. The normalized difference vegetation index (NDVI) is the most widely studied and used for mapping crop growth. A relatively expensive multispectral sensor is required to produce an NDVI map. The visible vegetation indices (VIs) derived from UAV images showed potential capabilities for predicting crop growth. The purpose of this paper is to evaluate the RGB indices to monitor the growth of the rice crop. The images were obtained from the study area by DJI PM4 multispectral UAV. The multispectral images were used to calculate NDVI as a reference vegetation index and different RGB indices were implemented and compared with the reference index. The results showed that RGB indices can be used as the vegetation index in the case of unavailable multispectral images.

Environmental and human health requirements necessitate replacing chemical herbicides with natural ones for weed control. Allelopathy is a form of interaction among plants that may assist in producing natural herbicides, but less research has been conducted in this important area. Allelopathic effects of extracts of five drought-tolerant plant species widely used in urban landscapes were examined using five completely randomized design experiments with four replications. The species were Rosmarinus officinalis, Lavandula officinalis, Salvia sclarea, Atriplex halimus, and Atriplex canescens. The plant species' soluble extracts were prepared at 0, 2.5, 5, and 7.5%. The seeds' germination percentage and rates of Taraxacum officinale, Conyza canadensis, and Tragopogon major were measured daily after being affected by these extracts. Increasing the concentrations of all the extract types was associated with germination percentages and rate declines. The most outstanding allelopathic effects were related to Atriplex halimus and Salvia sclarea extracts, respectively. Tragopogon major was considered the most sensitive weed species in reducing its germination rate when affected by the landscape plant extracts, except for R. officinalis extract. The reduction in germination percentage of T. major and C. canadensis under A. halimus extract compared to the control was the highest. A. halimus and S. sclarea extracts can be used as natural weed controllers for important weeds such as Taraxacum officinale.

Introduction Turfgrasses, as one of the important components of urban landscapes, have played a vital role in this regard. However, the main problems of turfgrass development are the cost of turfgrass seeds, maintenance costs such as moving, as well as the high water requirement in arid and semi-arid regions. Thus, the reduction of lawn culture in the landscape is one of the decision has taken in parks and green spaces organization of Tehran, Isfahan and even Mashhad. For over ten years, researchers have been looking for alternatives to conventional grass lawns to reduce the high cost of maintenance especially irrigation cost in urban landscapes. According to many researches, one of the potential ground cover alternatives that might be used instead of turfgrass is White Clover. Clover (Trifolium spp.) from Fabaceae family is a genus of about 300 species. Materials and Methods The aim of this experiment was to compare three common turfgrasses with two clover varieties as turf replacement to reduce landscape maintenance cost specially moving cost. So, some growth and qualitative factors of clover lawn: Trifolium repens var. Calway and Trifolium repens var. Pipolina (micro clover) and three turfgrasses of Festuca arundinacea L. and Lolium perenne L. and commercial sport turf mixture (from NAk-Nederland Ltd.) were compared together. This research was conducted in randomized complete block design with three replications in the research field of the Department of Horticultural Science and Landscape Engineering‚ Faculty of Agricultural‚ Ferdowsi University of Mashhad‚ Mashhad‚ Iran, during 2016 and 2017. The site (59º 38′ E and 36º 16 ′ N; elevation 989 m) is located in an arid and semi- arid region with mean annual rainfall 233.8 mm and long term averages of maximum and minimum temperature are 22.5 ºC and 9.3 ºC‚ respectively. Turfgrass plots were established by directly sowing the seeds in April, 2016. The planting rate of the seedling considering their pure live seeds (PLS) were 45 g.m-2 for Lolium perenne, 34 g.m-2 for Festuca arundinacea, 6.5 g.m-2 for Trifolium repens, 5.5 g.m-2 for micro clover and 39 g.m-2 for commercial mixture of sport turf. The plots were 1 m2 (1m×1m) in size and were prepared after plowing and leveling the soil. The seeds were hand sown and covered with a thin layer of leaf compost and sand. Results and Discussion According to the results in the first evaluation of emergence percentage, Lolium perenne had the highest emergence percentage. After 36 days from culture, all plants had 92-98 % coverage which did not have any significant difference among grasses with clover lawns. In terms of density, uniformity and weed density, there was no significant difference between the studied plants. In the other hands, white clover showed the best quality after clipping in both years. At the point of growth index, which have done in this experiment by measuring height and dry weight of clipping, grass lawns had the higher growth index in compered to clover lawn in both years. Festuca arundinacea and Lolium perenne had the highest growth index and white and micro clover had the lowest growth. Also, with air warming, Festuca arundinacea became dominated plant in height and clipping dry weight. In July, Festuca arundinacea produced the highest clipping dry weight by 40 gr.m-2, Lolium perenne (19.52), commercial sport turf (15.68), white clover (6.24) and micro clover (0.36) gr.m-2. Conclusion One of the problems of landscape is reduction of maintenance costs such as mowing. So, the low growth of white and micro clover is a positive factor in reduction of the moving costs than turfgrasses. Also, the coverage and proper density of clover lawns are similar to grass lawns and did not have a significant difference with them. The character of low growth can be effective in reduction of irrigation costs in white and micro clover, which requires more research and examination in future. This is a positive point in the white clover and micro clover that do not need to move or cut every months. Almost, clover moving is recommended for removing their flower. Therefore, it is recommended to use white and micro clover as a replacement with less maintenance costs in landscape. Finally, the results of cultivation of grass and clover as monoculture in this study can be used to produce clover-grass mixtures suitable for the climate of our country (arid and semi-arid regions), instead of importing turf mixtures from European countries.

High temperatures, low average rainfall, drought, and high evapotranspiration are limiting factors in arid lands. Therefore, when constructing landscapes (green spaces) in these regions, strategies should be developed to mitigate these climatic influences. One practical strategy is utilizing different types of mulches on the surface of the soil. This study was conducted as a randomized complete block design experiment with four replications during 2014 and 2015 to examine the performance of organic and inorganic mulches as non-living mulches and ground cover plants as living mulches. Ground cover plants were Carpobrotus sp., Potentilla reptans, Vinca minor, Frankenia sp. and a mixed turfgrass. Non-living mulches were turfgrass clippings, wood chips, sawdust, gravel, rubble and scoria (volcanic rock). Bare soil was used as the control treatment. The results demonstrated the application of mulches could modify soil temperature at 5 and 15 cm depths in different seasons of the year. The living mulches especially Carpobrotus sp. and turfgrass reduced the temperature more than the non-living mulches. The soil covered with sawdust and wood chips preserved soil moisture content over the soil covered with other types of mulches. It would appear the selected mulches could decrease the irrigation intervals through increased water holding capacity of the soil. The outcomes of this research could assist landscape managers operating in extreme climate conditions of arid and semi-arid regions to advance the management of soil moisture and temperatures with the objective to improve sustainability.