الفهرس 
INTRODUCTION
Effect of mulch treatmentOnly 14 pages are availabe for public view
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Abstract
The present experiment was carried out at the Experimental Farm of Vegetable Department, Faculty of Agriculture, Assiut University, Egypt. The experimental site located at 270 18’ latitude and 310 18’ longitudes and at an elevation of 70 meters above sea level. The soil texture of the experimental site was clay with a pH average of 7.65. Three irrigation regimes and mulch in five levels were used to avoid weed growth and for conservation of water on the ridges for the entire season from the date of sowing until harvest time. The irrigation treatments consisted of three irrigation periods: fully irrigated treatment (C), irrigation treatment stopped after 60 days from planting (IS 60) and irrigation treatment stopped after 30 days from planting (IS 30). The mulch treatments consisted of five mulches: clear plastic mulch (CPM), white plastic mulch (WPM), red plastic mulch (RPM), black plastic mulch (BPM) and a control that consisted of bare soil cultivated plants. Both factors, irrigation regimes and mulch treatments, will be investigated in the present study to estimate their effects on yield and quality of potato crop under Assiut conditions.
The obtained results could be summarized as follows:
1- The effect of the drought periods was not significant on the percentage of filed emergence in the two fall seasons of (2012/2013 and 2013/2014). Data in showed that stop irrigation 30 days after planting led to a lower number of emerged seed tubers (85.2 and 93.5) compared to the irrigation treatment stopped after 60 days from planting (87.8 and 96.1) in the first and second seasons, respectively. Percentage of germinated tubers was significantly lower for plants grown over clear mulch (CPM) compared to the other mulch treatments and the control treatment in both seasons.
2- The drought treatments had no significant influence on rate of filed emergence per plot. The lowest number of days until complete field emergence (25.5 and 27.0 days) were obtained from plots covered with black plastic mulch (BPE) compared to the non-mulched plots (35.8 and 39.9 days) in the first and second seasons, respectively.
3- There were no significant differences among the three tested irrigation regimes regard to the final number of plants at harvest time. Mulch treatment significantly affected number of final plant at harvest time in the two fall seasons. The highest number of plants at harvest time was recorded in both non-mulched treatment and white plastic mulch treatment. Moreover, the lowest values of harvested plants were recorded in the red polyethylene mulch whish were similar to that obtained from clear mulch plots.
4- The full irrigated treatments gave significantly the tallest plant in the first and second seasons, respectively. While the severest drought period (IS 30) gave significantly the shortest plant in the first and second seasons, respectively. Results of the two seasons as an average of all tested irrigation periods, indicated that average stem height values for the five mulch treatments followed the order BPE>RPE >WPE >CPE>C; average stem length was 60.3 cm, 57.6 cm, 57.5, 48.2 cm, and 43.7 cm, respectively.
5- In spite of the fact that our results were not significant, the higher number of stems per hill was always obtained from the full stress drought period (IS30) followed by the full irrigated treatment (C) in both seasons. Plots covered with white plastic (WPM) followed by (BPM) sheets significantly gave the highest number of stems per hill in both fall seasons.
6- Results indicated that the full irrigated treatment (control) gave significantly the highest total tubers yield per feddan. In addition, stopping, irrigation treatment after 30 days from planting (approximately at the end of the vegetative stage, VS) gave significantly the lowest total tubers yield per feddan in the two seasons. The total tubers yield obtained in the full irrigated plots (C) exceeded that of plants grown in plots irrigated till 30 days from planting (VS) by 59.63 and 59.82% in the first and second seasons, respectively.
7- Compared potato total yield between mulch and non-mulched treatments, the black plastic mulch (BPM) produced the highest total yield, with about 52.13% increases over yield on bare soil. Moreover, none of any plot covered with plastic mulch was lower than that in the corresponding control plot (hand weeding) regard to total tuber yields.
8- Full irrigated plots (C) gave significantly the highest average weight of tubers per plant (112.6 and 113.1 gm) compared to the other tested irrigation periods (IS 30 and IS 60) in the first and second seasons, respectively. The black plastic mulch gave significantly the highest average tuber weight in both seasons. Clear plastic mulch and hand weeding treatment significantly gave the lowest average tubers weight.
9- The highest marketable tubers yield per feddan was found in the stress-free treatment; however, the highest stress treatment (IS 30) produced the lowest average weight of marketable tuber per feddan in the two fall seasons. Mulched plots significantly out yielded non-mulched plots at all irrigation treatments. Black plastic mulch (BPM) significantly gave the highest yield of marketable tubers per feddan in the two fall seasons. However, the hand weeded plots (C) significantly produced the lowest yield of marketable tubers per feddan in the two fall seasons.
10- Results summarized that the unstressed treatment (control) which watered regularly to maintain soil moisture continuously near field capacity gave significantly the highest number of marketable tubers per plot (107 and 97) in the first and second fall seasons, respectively. The highest number of marketable tubers per plot was obtained in the white plastic mulch which was similar to the values obtained by the black plastic mulch and the lowest was obtained from the hand weeded treatment in the first and second seasons, respectively.
11- The lowest percentage of deformed potato tubers (highest yield improving) was obtained in the medium stress treatment (IS 60) followed by the severe stress treatment (IS 30) in the two fall seasons. Moreover, the unstressed plots significantly produced the highest percentage of malformed tubers (7.83% and 5.8%) in the first and second seasons, respectively. Black plastic mulch significantly improved the quantities (total yield character) and qualities of potato crop by decreasing the percentage of potato tubers show second growth (2.02 and 1.22 %) in the first and second seasons, respectively.
12- Full irrigated treatment significantly recorded the highest average foliage fresh weight per plot in the two seasons. The irrigation treatment (IS 30) produced the lowest average foliage fresh weight per plot in the two seasons. Results of the two seasons revealed that the highest average foliage fresh weight per plot was obtained from the red plastic mulch in both seasons. Moreover, the hand weeded plots gave significantly the lowest average foliage fresh weight per plot (4.63 and 3.41 kg) in the first and second seasons, respectively.
13- The control treatment gave significantly the lowest percentage of tuber dry matter in both seasons. Hand weeded plots significantly gave the highest percentage of potato tuber dry matter (29.88 and 28.56%) in the first and second seasons, respectively. In contrary, black plastic mulch significantly produced the lowest percentage of potato tuber dry matter (27.30 and 25.8%) in the first and second seasons, respectively.
14- Our data recorded that irrigation stress significantly increased the percentage of under-size tubers in medium stress condition ((27.8 and 22.7%) compared with stress-free condition (13.5 and 10.5) and high stress condition (13.5 and 10.6%). Bare soil treatment and clear plastic mulch produced the highest percentage of under-size tubers in both seasons, but the differences between the two treatments did not reach the significant level.
15- Full irrigated plots (20.7%) in the second season and the severe stress treatment (21.1%) in the first season significantly gave the highest percentage of foliage dry matter of potato. In one hand, plots covered with black plastic sheets (BPM) gave significantly the highest percentage of foliage dry weight (23.9 and 24.4%) in the first and second seasons, respectively. On the other hand, hand weeded plots (C) produced the lowest percentage of foliage dry weight (17.3 and 14.9%) in the first and second