الفهرس | Only 14 pages are availabe for public view |
Abstract Two field experiments were conducted during the spring season through two successive years, 2007 and 2008, at El-Shiekh Zowyeid Research Station, Desert Research Center to evaluate the effect of applying three rates of crop evpotranspiration (ETc) throughout three growth stages of tomatoes , individually and in combinations with selected twelve treatments of deficit irrigation and four levels of N and K fertilization rates on the yield production .some growth and quality parameters and some water requirements measures under water and fertilization stress of tomato (strain B, Lycopersicon esculentum L.) B. The applied treatments include: Three deficit irrigation doses (100, 80 and 60 % of crop water requirement) were applied through three plant growth stages (development, mid and late growth stages) as follow: I. D1 = Irrigation with 100 % ETc through the three growth stages. D2 = Irrigation with 100 % ETc through the development and late stages and irrigation by 80% ETc at mid stage. D3 = Irrigation with 100 % ETc through the development and late stage and irrigation by 60% ETc at mid stage. D4 = Irrigation with 100 % ETc through the development and mid sages and irrigation by 80% ETc at late growth stage. D5 = Irrigation with 80 % ETc at the development stage and irrigate by 100% through mid and late growth stages. D6 = Irrigation with 60 % ETc at the development and irrigate by 100% through mid- and late growth stages. D7 = Irrigation with 60 % ETc through the development and mid and irrigation with100% at late growth stage. D8 = Irrigation with 60 % ETc through the development and late and irrigation with 100% ETc at mid growth stage. D9 = Irrigation with 60 % ETc through the three growth stages.D10 = Irrigation with 80 % ETc at the development and irrigate by 100% and 60 % at mid-and late growth stages, respectively. D11 = Irrigation with 80 % ETc through the development and lateseason, while irrigate with 100% at mid-season growth stage. D12 = Irrigation with 60 % ETc through the three growth stages. II. Four fertilization rates as follows:: F1 :100 kg N/fed and 120 kgK2O /fed. F2 :100 N/fed and 60 kgK2O /fed. F3 :50 N/fed and 120 kgK2O /fed . F4 :50 N/fed and 60 kgK2O /fed The obtained results summed up as follows: I. Effect of deficit irrigation: The weight of both fruit yield and fresh shoot, moisture contents and growth parameters of tomato decreases with increasing deficit irrigation during the stages of growth, Applying deficit irrigation during one growth stage is much better than two and three stages. The weight of dry fruits and shoots showed reversed trend for fresh weights either fruits or shoot where the dry matter increased with the less decrease of the applied water (20% ETc) at the late growth stage Tomato quality fruit parameters (acidity and electrical conductivity and total dissolved solids) showed positive moral response where, the values increased with increasing water deficit especially, soluble solids while the acidity was slightly affected. The application of deficit irrigation at one growth stage decreased concentration and uptake of N,P and K in tomato fruits the least values were achieved by applying 80% ETc in the late growth stage in both seasons Applying deficit irrigation at two growth stages decreases the concentration and uptake of N, P and K with the maximum decreases when adding 60% ETc . Applying irrigation (80 or 60%) for three growth stages led to the largest decreases in concentrations and uptake of N, P and K. The actual evapotranspiration (ETa) of tomato plants was affected by decreasing the applied water throughout the different growth stages The application of deficit irrigation ( 80% ETc) in both development and mid-season growth stages decreased ETa less than its application in the development and late season growth stages Applying irrigation (80 or 60%) ETc for the three growth stages of tomato, decreased ETa less than applying 100% The water use efficiency of tomatoes increased when applying 100% ETc relative to applying 60% ETc for three growth stages while the magnitude of decrease is less when applying 80% ETc at the late growth stage relative to development growth stage Water use efficiency decreased by applying 20% deficit of ETc in the development stage and late season < development and midseason < 60% ETc development and the late season< 60% ETc for the three growth stages The lowest WUE for dry tomato plants corresponds to 80 % ETc during the development and mid-season growth stages while the maximum WUE was confined to the smallest irrigation water amount , 60% ETc., in the three growth stages. The highest Weco.. of dry production was achieved by applying the minimum irrigation water quantity (60% ETc) while the lowest was obtained when the irrigation water decreased to 80 % ETc at mid- season growth stage. II. Effect of fertilization rates: All tomato growth parameters were affected by the rate of N and K fertilization where they increased with increasing the rate of added N while, the impact of K doses was slight but significant. All fresh and dry weights of fruits and shoots , growth and quality parameters of tomato increased significantly by adding fertilization rates. The concentrations and uptakes of N, P and K in fruits and shoots of tomatoes decreased according to decreasing the doses of N and K Increasing the amount of added N and K led to the increase of the daily actual evapotranspiration in each stage and the whole season as such. The water use efficiency of tomato increased gradually with increasing the applied fertilizers rate Increasing the application of N fertilizer has a pronounced effect on the increase of WUE compared to the increasing rate of K fertilization. The highest Weco. for fresh and dry fruits of tomato is associated with applying the largest rate of both N and K fertilizers,. Increasing N application has a considerable effect on increasing the Weco of tomato compared to the increasing rate of K fertilization. III. Combined effect of deficit irrigation and fertilization : Firstly, one should to mention that all comparisons were conducted relative to the control (D1 F1) unless otherwise stated. The minimum decrease in fresh weight of tomato yield was obtained by applying D1 F2. Moreover, the decreases were maximized when tomato plants were irrigated by D12 F4 The yield of dry tomato fruits followed the same trend of the fresh fruits yield, On the other hand, the slight decrease in irrigation (D4 F1 and D5 F1) caused a significant increase in dry weight. The fresh and dry tomato shoots followed the same trends already mentioned for the fresh fruits . All growth parameters of tomato plants decreased slightly by applying D4x F1 and this effect was more apparent with decreasing the applied fertilizers rate Reducing N fertilization rate led to more correspondent decreases in all growth parameters, especially when the N fertilizer decreased to the half dose F3 ( D5 F3 and D6 F3). Applying D7 F1, decreased plant height, fruit diameter, number of leaves and leaf area index more than D8 F1 Applying 40 % deficit regime at the three growth stages caused the highest decreases in all studied parameters relative to 20 % deficit regime. Applying D3 F1 increased TSS in fruit more than D4 , ,D5 , D6, D8 and D11 with F1. Also, applying D7 F1 increased EC, pH and TSS in fruit relative to D11 F١ . Moreover, applying D9 F1 increased remarkably TSS in fruit while, EC and pH were nearly unaffected Applying D5 F1 led to a pronounced decrease in both the concentrations and uptake of N,P and K in fruit. Likewise, applying D6 F1 decreases their concentration and uptake in different magnitudes. Decreases of D2 F1 N,P and K in fruits on applying D2 F1were almost close to D3 F1 . Generally, applying an increasing pattern of deficit irrigation with constant fertilization rate (F1) led to a pronounced decrease of N,P and K , however, the magnitude of was decrease more considerable at the higher rates of deficit irrigation . The minimum ETa value at mid- season growth stage was obtained when applying D3 F4 in the two seasons. Decreasing the applied irrigation water depth by 20 % ETc at development growth stage caused a pronounced decrease in ETa in both seasons. Applying 80% ETc at the late growth stage caused a slight decrease in ETa in the two seasons. Applying D9 F1 decreased ETa at each of development, mid and late growth stages as well as total season less than applying (D12 F4). Both development and late growth stages were the most sensitive to water stress. The tomato yield is correlated significantly with plant water consumption at all growth stages and total season except the dry fruit in both development and late-season growth stages of the two seasons. The largest decrease of WUE was obtained when plants were irrigated by 60 % ETc (D6) with applying the lowest fertilization rate (F4) A slight decrease was recorded for WUE of fresh fruits when plants were irrigated with 80 % ETc through late growth stage with applying the highest rate of fertilizers (D4 F1). Applying 20 % or 40 % deficit irrigation especially, with decreasing the fertilization rate at mid growth stage caused a decrease in WUE for the dry weight of fruits with the maximum decrease at the mid growth stage when applying 40 % deficit irrigation (D3 F4) . Applying irrigation by 80% of ETc at development and / or late growth stages and adding the two higher rates of fertilization led to increasing WUE of fresh and dry fruits. Using the applied irrigation water dose at 80 % ETc in conjunction with high fertilization rate through both development and mid growth stages (D7) had further decreased WUE for fresh tomato fruits. Align with this, applying deficit irrigation through both development and late stages with adding the two higher fertilization rates increased the WUE of dry fruits . The largest decrease in WUE by fresh tomato fruits was obtained when applying high deficit irrigation rate (60 % ETc) and / or decreasing the fertilization rate through both development and late growth stages. Applying 20 % deficit irrigation through both development and mid- season stages (D7) caused a decrease in WUE especially with decreasing the fertilization rate in the two seasons upon applying (D7 F4). In contrast, applying deficit irrigation through both development and late- season stages with adding the two higher fertilization rates increased the WUE of dry fruits Applying 20% and 40% ETc deficit irrigation together with N & K fertilization at all growth stages decreased the WUE by fresh fruits, especially with decreasing the applied fertilization rate. The highest Weco of fresh tomato fruits was rendered to 20 % deficit irrigation at late- season D4 F1 , relative to the lowest Weco. obtained by applying the D12 F4 in the two seasons. In contrast, the dry tomato fruits recorded the maximum Weco. when plants were irrigated by 40 % deficit regime through the studied three growth stages (D12F2) relative to D12 F4 There were highly significant positive simple correlations among the fresh and the dry weights of fruit yield and the fruit moisture content vs soil variables, EC and pH of irrigation water The fresh weight of tomato yield is highly significant positively correlated with N fertilization, N and K concentration in fruit and seasonal ETa while being significant negatively correlated with EC and pH of soil The dry weight of tomato yield is highly significant positively correlated with EC irrigation of water, N,P and K concentrations ,in fruit and seasonal ETa while being significant negatively correlated with EC and pH of soil The moisture content of tomato yield is highly significant positively correlated with N,P and K concentrations ,in fruit and seasonal ETa while being significant negatively correlated with EC and pH of soil . |