EFFECT OF IRRIGATION LEVELS, CULTIVATION METHODS AND PLANT DENSITIES ON PRODUCTIVITY, QUALITY OF ONION CROP AND SOME WATER RELATIONS IN HEAVY CLAY SOILS

Abstract

A field investigation was conducted at Sakha Agricultural Research Station during the successive winter growing seasons 2012/13 and 2013/14 to study the effect of irrigation levels, cultivation methods and plant density on productivity, quality of onion crop and some water relations in heavy clay soils. A strip split plot design with four replications was used in this present study, where, the horizontal plots were assigned to irrigation treatments which were, I0 (Traditional irrigation, like practice by local farmers in the studied region), while, I1, I2 and I3 irrigation at 90, 80 and 70% of field capacity, respectively. While, the vertical plots were also randomly assigned by cultivation methods which were, A (Cultivation on raised-beds) and B (Cultivation on normal furrows). Sub-sub plots were randomly assigned by plant densities which were D1 (30 plants/m²), D2 (45 plants/m²), and D3 (60 plants/m²) under the two cultivation methods. The main results can be summarized as follows: The results showed that the plants irrigated at 80% of field capacity, produced the highest average bulb weight, onion bulbs yield and good quality bulbs with the highest values of remainder bulbs% at the end of storage periods. Marketable and total bulbs yield increased above 25.72 and 33.84 % resulted from plots irrigated at 80% of field capacity as compared to traditional irrigation as an average for the two seasons. Abundance of the available soil moisture (Traditional irrigation like practice by local farmers in the studied area) significantly increased N, P, K and Zn contents of onion bulbs as well as culls yield, physiological, decay, sprouting losses and final loss % of onion bulbs at three storage periods in both seasons.  Concerning, the effect of cultivation methods on average bulb weight, marketable and total bulbs yields as well as bulb diameter, TSS and dry matter % were evident in both seasons. In general, all the previous characters positively increased significantly with raised-beds than normal furrows. On the contrary, the culls yield, N, P, K and Zn contents were significantly higher under normal cultivation method, and the lowest with raised-beds cultivation method. Also, the lowest values of physiological loss, decay and sprouting losses % of onion bulbs at three storage periods were obtained under raised-beds cultivation method. Culls yield decreased above 19.16 % in the plots transplanted on raised-beds as compared to normal furrows methods as average for the two years. Results revealed that increasing population of onion plants from 30 plants/m2 to 45 plants/m2 gradually decreased average bulb weight and bulb diameter as well as physiological, decay and sprouting losses % and final loss % at three storage period. However, the medium planting density of 45 plants/m2 compared to lower planting density of 30 plants/m2 led to an increase inmarketable and total yields per fed., TSS and dry matter % above 17.08, 22.26, 10.71 and 14.21%  as an average for the two years, respectively. The inverse was true in culls yield, where 60 plants/ m2 gave the highest of culls yield above 88.22 % compared to 30 plants/m2 as an average for the two years. The first and the second order interaction had a significant effect on yield and storability. The maximum yield and the best quality with the highest remainder bulbs% at the end of storage periods were achieved from plants irrigated at 80% of field capacity and grown at 45 plants/m2 with raised-beds cultivation method in both seasons. The highest overall mean values through the two growing seasons for seasonal water applied, water consumptive use and consumptive use efficiency were recorded under irrigation treatmentsI0 (Traditional irrigation) and normal cultivation method (B) and the values are 56.63 cm (2378.38 m³/fed.), 51.86cm (2177.82 m³/fed.) for seasonal water applied, 36.61cm (1537.73 m³/fed.) for water consumptive use and 64.66% and 63.38% for consumptive use efficiency under normal cultivation method and raised-beds, respectively. Meanwhile, the lowest values were recorded under irrigation treatment I3 (water stress conditions) and raised-beds cultivation method and the values are 40.01cm (1680.52 m³/fed.), 36.23cm (1521.48 m³/fed.) for seasonal water applied, 24.62cm (1033.97 m³/fed.), 21.88cm (919.14 m³/fed.) for water consumptive use and 61.53% and 60.41% for consumptive use efficiency under normal cultivation method and raised-beds, respectively. Regarding, the effect of plant densities, the highest values for water consumptive use and consumptive use efficiency were recorded under the highest density D3 (60 plants/m²) under the two cultivation methods and all irrigation treatments. Concerning, the values of seasonal water applied were not affected by plant densities treatments. The highest overall mean values for water productivity (WP, kg/m3) and productivity of irrigation water (PIW, kg/m3) were recorded with irrigation treatment I2 (irrigation at 80% of field capacity), raised-beds cultivation method (A) and plants density (45 plants/m2). Meanwhile, the lowest values for WP and PIW were recorded under I0 (traditional irrigation), normal cultivation method (B) and plant density (60 plants/m2). It can be concluded that the irrigation at 80% of field capacity with a population of 45 plants/m2 under raised-beds cultivation method was the recommended treatments for optimum productivity, quality of onion and remainder bulbs% at the end of storage periods and maximizing water productivity (WP, kg/m3) and productivity of irrigation water (PIW, kg/m3) at Kafr El-Sheikh Governorate conditions.