چكيده لاتين :
Introduction: In natural environments, plants are subjected to biotic (insects, bacteria, fungi, and viruses) and abiotic (light, temperature, water availability, nutrients, and soil structure) stresses that can have negative effect on growth, metabolism, and yield. Among these, drought is a major abiotic factor that limits agricultural crop production. Potato production has fourth rank in the world after rice, wheat, and maize with the production of 321 million tons from 19.6 million hectares. By about 3 percent of cultivation area, potato had 7.2 percent of total agricultural production (5.57 million tons) in our country (Iran). Limited studies have been conducted on the interactive effects of Zn and P on potato tubers quality under water deficit conditions.
Materials and Methods: This study was conducted for evaluating the effects of soil moisture, phosphorus (P) and zinc (Zn) levels on the chemical composition and nutrients content of potato (Solanum tuberosum L. cv. Agria) as a factorial experiment based on randomized complete blocks design with three factors under greenhouse conditions. The study was performed with factors of Zn at three levels (0, 10 and 20 mg Zn per kg dry soil as ZnSO4.7H2O), P at three levels (0, 30 and 60 mg P per kg dry soil as Ca(H2PO4)2.H2O (monocalcium phosphate)) and soil moisture at three levels (0.5FC-0.6FC, 0.7FC-0.8FC and 0.9FC-FC) using three replications and 81 pots. The soil moisture levels were imposed three weeks from the flowering (64th day) until harvest (85th day after planting). After imposing of soil moisture levels and at the harvest, the yield and yield components, reducing sugars concentration in fresh weight by di- nitro phenol method (Mostofi and Najafi, 2005) and starch by Antron method (Mostofi and Najafi, 2005), N, P, K, Mg, Na, Fe and Zn concentrations in dried potato tubers were measured. Data were subjected to analysis of variance as factorial 3×3×3 with n=3 by using MSTATC software. Duncan 's multiple range tests at p≤0.05 probability level was applied to compare the mean values of measured attributes. The Excel software was used to draw Figures.
Results and Discussion: The results showed that water deficit significantly affected most of qualitative attributes and nutrients concentration of potato Tuber N, P and reducing sugar concentrations were significantly increased (p <0.05) with reducing soil moisture content. This increase was 10, 10 and 18 percent for severe water deficit condition (0.5 FC - 0.6 FC) comparing with full irrigated level (0.9 FC - FC), respectively. Severe water deficit condition reduced tuber Na, Mg, Fe and starch concentrations, 20, 30, 21 and 20 percent comparing with full irrigated condition. The imposed soil moisture levels had no significant effect on tuber K and Zn concentrations. Zn application significantly affected Na, Fe, Zn and starch concentration of potato tubers but had no significant effect on N, P, K, Mg and reducing sugars concentrations. Application of 20 mg Zn per kg soil increased significantly (p <0.05) tuber starch, Na, Fe and Zn concentrations by 15, 14, 36 and 8 percent comparing with without Zn application, respectively. Phosphorus usage also affected significantly N, P, reducing sugars and starch concentrations of potato tubers while had no significant effect on K, Mg, Na, Fe and Zn concentrations. Application of 60 mg P per kg soil decreased significantly (p <0.05) tuber N concentration (14 percent) and increased starch, reducing sugars and P concentrations (8, 11 and 10 percent, respectively) of potato tubers comparing with without P application condition. Two way interaction of P × soil moisture was significant on tubers P, N, Fe and Zn concentration. Also, two way interaction of P × Zn was significant on tubers P and N concentration. Three way interaction of P × Zn × soil moisture was significant on tubers N and Zn concentration too. The results showed that the two way interactions of Zn, P and soil moisture were mainly synergistic on the most of above mentioned attributes that significantly were affected by imposed factors.
Conclusion: The results showed that water deficit imposing had adverse effects on tubers quality and P and perhaps Zn requirement enhanced by increasing of water deficit. In general, to achieve the optimum potato tuber yield in similar soils, application of 10 mg Zn and 30 mg P per kg dry soil would be recommended under normal irrigation conditions while at water deficit conditions application of 10 mg Zn and 60 mg P per kg dry soil could be recommended.
