عنوان مقاله [English]
Introduction: In Iran, due to reduction of water resources and increasing of water losses in the various methods of the surface irrigation pressurized irrigation methods, especially drip irrigation have got many attentions. Application of the plastic mulch method is used in cultivation of early sweet corn. Application of this technique due to its temperature provides both plant growth and early maturity and then causes the on-time delivery of product to the target market. Additionally, to reduce water consumption, the use of germinated seedlings in the greenhouse and move it under plastic on the farm, productivity will increase. The aim of this study was to evaluate irrigation levels on yield of sweet corn by using plastic mulch, and the feasibility of seedling cultivation to early crop.
Materials and Methods: In order to evaluate the effect of different irrigation levels and cultivation techniques on water use efficiency and quality and quantity yield of sweet corn, an experimental program was carried out as split plot in randomize complete blocks design with three replication in Faculty of Agriculture, Research Field Station of Yasouj University in 2015. The main factor consisted of three levels of irrigation: 100 (I1), 75 (I2) and 50 percentage of water requirement (I3) and the sub-factor was including cultivation techniques of sweet corn in six levels: seed cultivation of sweet corn under plastic mulch on 4 April (CT1), seedling cultivation under plastic mulch on 4 April (CT2), seed cultivation to conventional method of sweet corn on 5 May (CT3), seed cultivation of sweet corn under plastic mulch on 5 May (CT4), seedling cultivation of sweet corn under plastic mulch on 5 May (CT5) and seedling cultivation to conventional method of sweet corn on 5 May (CT6).
In order to establish plastic mulch, after seed and seedling cultivation of sweet corn with installation of irrigation tape tubes, steel bars which were made in a semi-circular shape, were placed on rows and plastics were laid on it. After the establishment of the seedling on the farm, the irrigation levels were applied by volumetric counters. When the plant height was equal to the height of plastic tunnels, it was tried to pierce the plastic to grow suitability. During the time of maturity product, a 2 m2 plot in the middle of farm was selected and the ears were separated and weighed, and the forage yield was weighted. The grains of sweet corn were separated and canned yield was measured. The content of grain sugar, sucrose and fructose were measured by means of HPLC method, and the content of grain nitrogen with using of micro Kjeldahl’s method achieved. Statistical analysis was performed using SAS software. The mean values were compared by using LSD multiple range tests at 5% level. Figures were depicted by using of Excel software.
Results and Discussion: The results indicated that irrigation interaction and cultivation techniques were significant on ear yield, the canned yield, water use efficiency, and forage yield. The maximum ear yield obtained in treatments of I2CT1, I1CT1, I2CT2 and I1CT2 were equal to 14420, 14414.4, 13691.7 and 13513.5 kg ha-1, respectively and the maximum water consumption content for mentioned treatments were equal to 2521, 3362, 2385 and 3180 m3 ha-1, respectively. The minimum ear yield obtained in treatment of I3CT3 was equal to 706 gm-2. Water stress delayed the physiological processes including silk rating and tassel emergence, so that, it reduced growth and plant height and finally leaded to the reduction of grain yield. The maximum canned yield were obtained in treatment of I1CT1, I2CT1, I1CT2 and I2CT2 equal to 558.7, 551.1, 536.2 and 527.4 gm-2, respectively. Higher grain yield of sweet corn under plastic mulch in comparison with non plastic mulch, was due to increasing of dry matter accumulation before the silk production. It seems that increasing temperature and water content under plastic mulch resulted in an increase in grain dry matter accumulation. The maximum water use efficiencyfresh grain was obtained in treatment of I2CT2, I2CT1, I3CT2 and I3CT1 equal to 2.21, 2.18, 2.16 and 2.14 kgm-3, respectively. With increasing of water consumption water use efficiencyfresh grain decreased. Maximum forage yield was obtained in I1CT1 equal 2008 gm-2 and minimum forage yield was obtained in I3CT6 equal 1237 gm-2. Available water under plastic mulch, increased plant growth by increasing of leaf area index and shoot biomass due to stomata opening.
The effect of irrigation were significant on grain sucrose percentage, and content of protein. Moreover cultivation techniques effect was also significant on content of grain sugar, sucrose percentage and subsequently the content of grain protein. The maximum grain sucrose percentage was for treatment of 100% water requirement of sweet corn which was equal to 4.92%. Treatment of 75 percentage water requirement, also, the minimum grain sucrose percentage equal to 4.11% was obtained in treatment of 50 percentage water requirement. Retaining of moisture increased the amount of sugar and grain sucrose content. The maximum content of grain protein was equal to 11.41% in treatment of 100 percentage water requirements; also the minimum content of grain protein equal 8.58% was obtained in treatment of 50 percentage water requirement.
By reducing soil moisture, the content of protein and sugar grain increased, so the maximum content of grain protein and sugar were obtained in treatment of 50 percentage water requirement, although the maximum levels of irrigation reduced the content of protein and sugar. Under stress conditions, the plant material requirement is not enough, so by reducing nutrient transport, the leaf and stem cell development delayed, resulting in reduced plant height, leaf area, the content of grain protein, sugar. Finally, dry matter accumulation in the grain decreases with the transfer of nutrients from the leaves, and then it caused early death the leaf.
Conclusions: Application of seedling and plastic mulch accelerated plant growth, its development and then it was out of season production. If there are not water restrictions, application of treatment of 100 percentage water requirement of sweet corn with plastic mulch is desirable to maximum yield produce. Average of water consumption was in treatments of plastic mulch and non-plastic mulch equal to 2735 and 3411 m3 respectively. Maximum content of grain protein and sucrose percentage were obtained in treatments contains plastic mulch. Seedling cultivation in comparison with seed cultivation showed minimum content of grain sugar and grain sucrose percentage. In order to achieve the maximum quality and quantity yield in areas that are faced to water restriction, it is possible to use treatment of 75 percentage of water requirement and seeding cultivation under plastic mulch.