ABSTRACT
Irrigation management strategy invites the quantification of crop response to irrigation frequencies. Conventionally, mulches increase the yield and water use efficiency (WUE) to a great extent by augmenting the water status in the root zone profile. A field study was carried out during the winter season (November–March) of 2003–2004 and 2004–2005 at the Central Research Farm of Bidhan Chandra Krishi Viswavidyalaya (Latitude 22◦ 58r N, Longitude 88◦ 31r E and altitude 9.75 m amsl), Gayeshpur, India, to eval- uate the effect of irrigation frequencies and mulches on evapotranspiration rate from tomato crop field as well as leaf area index (LAI), fruit yield and WUE of the crop. The experiment was laid out in a split-plot design where three irrigation treatments {rainfed (RF); CPE50 and CPE25 where irrigation was given at 50 and 25 mm of cumulative pan evaporation (CPE)} were kept in the main plots and the subplots contained four mulch managements {no mulch (NM), rice straw mulch (RSM), white polyethylene mulch (WPM) and black polyethylene mulch (BPM)}. Under CPE25, tomato crop recorded significantly higher leaf area index (LAI) over CPE50 and rainfed condition. LAI value under BPM was 9–30% more over other mulches. Maximum variation of LAI among different treatments was recorded at 60 days after transplanting (DAT). Fruit yield under CPE25 was 39.4 Mg ha−1; a reduction of 7 and 30% has been obtained under CPE50 and RF condition. The use of mulch increased 23–57% yield in comparison to NM condition. Actual evapotranspiration rate (ETR) was 1.82 mm day−1 under CPE25 and declined by 15 and 31% under CPE50 and RF condition, respectively. The variation of ETR among different mulches became more prominent under maximum water stressed (RF) condition, whereas the variation was negligible under CPE25 frequency. Irrespective of mulching WUE was highest under moderately wet (CPE50) soil environment. Among different mulches, BPM was responsible for attaining the highest WUE value (25.1 kg m−3 ), which declined by 22, 21 and 39% under WPM, RSM and NM, respectively.
CHAPTER ONE
INTRODUCTION
1.1 Background of the study
Tomato is considered as one of the important commercial vegetable crops grown in India. The total land area under cultivation of this crop was 290.28 thousand ha during 1990 and the area increased to 479.2 thousand ha within a span of 17 years (FAO, 2009). Productivity level of tomato in the country is 17.91 Mg ha−1, which is 13% less than that of the global average. Though this is a remunerative crop in the Lower Gangetic Plains (LGP) of eastern India, its average productivity is 5% less than that of the National level (Economic Review, 2007–2008). Till date, in the LGP water scarcity has not crept in, resulting in lavish use of irrigation lead- ings to over exploitation of ground water resource and lower water productivity level for vegetable crops (Sarkar et al., 2008). The normal annual rainfall of the area is 1560 mm, out of which 150 mm received during winter months. However, since last ten years, only 52 mm occurs during winter months. Besides, cultivation of summer rice (January–April) under irrigated condition responsible for lower down of ground water table by 1.5 m in last 10 years (Goswami, 2005). Thus, an urgent need has been felt to increase the productivity of the vegetable crops with a concomitant con- servation of water resource to justify the demand of more crop per drop of water. Since last few decades, water use efficiency (WUE) level has been enhanced through breeding of high yield- ing cultivars and managing the soil resource in an effective way. In contrast, little progress has been made in keeping the yield at higher level even with the minimization of actual evapotranspiration (ETC). In irrigated ecosystem, amount of total irrigation determines the quantum of seasonal evapotranspiration (Wang et al., 2005). Besides, frequency of irrigation plays a crucial role on growth and yield of tomato (Obreza et al., 1996). At this moment, demand for water in other sectors is increasing; as a result share of irrigation is continuously decreasing. Due to this, irrigation scientists are forced to develop water saving irrigation strategies (Payero et al., 2009).
