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Author : Tarawalie Ismail Foday, Wengang Xing, Guangcheng Shao, Chunli Hua
International Journal of Scientific & Engineering Research Volume 3, Issue 1, January-2012
ISSN 2229-5518
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Abstract— Partial root-zone drip irrigation was tested to investigate effect of water use efficiency on growth and yield of hot pepper in a greenhouse condition. This study was conducted to compare effect of partial root-zone drip irrigation (PRDI) and examine how it affected soil water distribution, water use, growth, photosynthesis rate, stomatal conductance, transpiration rate and yield of hot pepper. The experiment was designed with three irrigation Schedule of 30%, 50% and 100% of ETo respectively, on four stages of plants growth; (i) Seedling and vegetative, (ii) flowering and fruit setting (iii) Vigorous fruit bearing (iv) Late fruit bearing. Irrigation water amount was calculated according to daily evaporation. There were nine treatments rows and irrigation was carried out three times per week.Results showed that, the average moisture content on both sides on each treatment was relatively constant or rose slightly as the highest was 25.20±0.23 and the lowest 21.05±069 for the right side while for the left side the highest was 24.66±0.68 and the lowest 21.59±0.22 as shown in table 3.2 and 3.3. High photosynthesis rate was recorded in treatment 1 with an initial irrigation schedule of 30% of ETo at seedling and vegetative growth, whereas, high stomatal conductance and transpiration rate were recorded in treatment 9 (control row) with 100% irrigation schedule of ETo throughout the four stages of plant growth. At 150 days after transplant hot pepper plants were harvested. The result further showed that moderate water at 50% of ETo  during Vigorous fruit bearing can increase yield production and this was manifested in Treatment seven with irrigation schedule of 50% of ETo had the highest harvest yield of  3501g followed by treatment 9 (control) with 2982g and the lowest was recorded on treatment 6 with 1239g.The result also indicated that, treatments  1 and  8 also responded low to yield with 1489.86g and 1506.17g respectively, and also to dry biomass and water use efficiency, however, treatments 4, 2 and 3 recorded moderate yield. Fig 3.6 gives the full details of data analysis on yield, dry biomass and two water use efficiency.

Index Terms— partial root-zone drip irrigation; irrigation frequency; water use efficiency (WUE); hot pepper; growth stage; ETo Evapotranspiration

1   INTRODUCTION                                                                     
It would be much difficult to meet the food requirements in the future with the declining water resources and li-mited clean water reservoirs in the future, as 70% ~ 90% of the available water resources is used in food production. To cope with the water shortage problem, it is necessary to adopt effective water-saving agricultural countermeasures [19]. Efficient use of water by irrigation is becoming increasingly important. Agronomic measures such as varying tillage practices, mulching and anti-transpirants can reduce the demand for irrigation water and improve irrigation water use efficiency (IWUE). Development of novel water saving irrigation techniques represents another option for increase water use effi-ciency.

During the last two decades, water–saving irrigation tech-niques such as deficit irrigation (DI) and partial root zone drying (PRD) or alternative irrigation (AI) have been widely developed and tested for field crops and fruit trees. Most recently, these irrigation techniques are also being tested in vegetable crops such as tomatoes and hot pepper etc. [23]. In this paper, the principles of water-saving irrigation strategies such as the PRD mode and it’s prospective for improving irrigation and crop water use efficiency in horticultural and agricultural production were discussed.
Particularly, the effective use of irrigation water has become a key component in the production of field crops and high-quality fruit crops in arid and semi-arid areas. Irrigation has been the major driving force for agri-cultural development in these areas for some time. Efficient water use has become an important issue in recent years under the critical situation of water resource shortage in some areas. Much effort has been paid to develop techniques such as RDI (regulated deficit irri-gation), CAPRI [controlled alternate partial root-zone irrigation or partial root-zone drying (PRD in the literature)] to improve field and fruit crop water use efficiency [5], [6], [16], [17], [20], [9].

The natural soil has been constituted by physically and chemically weathered consequence of the rock, therefore it exists universally in nature. The Earth’s surface layer with about 0.5-1.0m deep is constituted by soil and organic humus; it is often used for cultivation, and then called as the agricultural soil. Water takes up a higher percentage of the world and plays a key role in making earthly temperature equilibrium and concurrently being a main factor for changing the conformation of the earthly surface ceaselessly.

Nowadays, the tendency to develop irrigation in many countries is the sensible exploitation of existing hydraulics project systems and strengthening on the depth of irrigation techniques and methods to raise economic effect based on the utilizable effect of water resources. Selection and application of a sensible irrigation method is directly effective and of critical importance because irrigation techniques play a crucial role in water supply and distribution for crops directly and decide water losses in some extent at the field.

Besides, the current common irrigation techniques, such as flood and canal irrigation etc, still have a high degree of water losses.

Increasing water use efficiency (WUE) is one of the main strategic goals for worldwide researchers as well as decision makers due to water scarcity and continuing high demand of water for agricultural irrigation. With the low efficiency of irrigation water utilization,   about another more 50% percent water is required; indeed which part could be met by increasing the effectiveness of irrigation. However, the agricultural irrigation uses over 70% of the world clean water and most of which is specially used in the protected environment [11]. Meantime, it is quite costly to use clean water and chemical solutions as fertilizers. In addition, the fast growing industrial sector competes with agriculture for water resources and the pollutants emitted became the source of most water pollution, which will push the agricultural activities to remote areas where there might be water scarcity and salinity as major problems.

The basic purpose of irrigation is supply of enough water into soil to ensure crops have the best development and growth. Traditional popular irrigation methods do not maintain suitable moisture for crop requirement in developing and growing, the extent of change in soil moisture is fairly significant (higher or lower than suitable moisture). Water saving irrigation technique is the best water supply technique and contributing to considerably higher productivity and quality of crops. Therefore, the development of water saving irrigation technology is urgent, and it will open up glorious prospects to plant industrial crops, fruit-trees, vegetables and other crops that have high economic values.

Traditional irrigation principles and methods have been challenged and modified [14]. Ideally WUE should be improved by reducing leaf transpiration. Stomata control plant gas exchange and transpiration/water loss and investigation has shown that stomata may reduce their opening according to the available amount of water in the soil [3], [22]. The advantage of such a regulation is that the plant may delay the onset of an injurious leaf water deficit and so enhance their chance of survival with unpredictable rain-fall, the so-called optimization of water use for CO2 uptake and survival [12], [2]. Recent evidence has shown that such a feed-forward stomatal regulation works through a chemical signal, the increased concentration of abscisic acid (ABA) in the xylem flow from roots to shoots. Part of the root system in drying soil can produce a large amount of ABA while the rest  of the root system in wet soil can function normally to keep the plant hy-drated [23]. The result of such a response is that, plant can have a reduced stomatal opening in the absence of a visible leaf water deficit.

In this study, in order to determine the effect of partial root-zone drip irrigation on hot pepper plants growth in a green house, an efficient partial root-zone irrigation field work was designed and carried out at a greenhouse of Key Laboratory of Agricultural Engineering Water saving-park at Jiangning campus of Hohai University, Jiangsu Province, Nanjing, China. In this experiment, quantitative monitoring of indoor positioning systems and practical validation approach and mechanism combined with production practice were applied.

As in the term “partial root-zone drip irrigation”, “partial” means that at least some part of the soil water content was controlled above a certain percentage of their field capacity and the root system was divided into two parts, North and South and water was applied to the parts.
Nine rows were established with 22 plants per row, com-parisons were made in terms of plant growth, shoot physiology and water use efficiency (WUE) using irrigation frequencies; 30%, 50% and 100% respectively at various growth stages.

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