The effect of urea and solopotass on morpho-physiological and biochemical characteristics of Super Sweet Corn (Zea mays var Basin) in response to different irrigation regimes

Maize (Zea mays L.) is widely spread all over the world due to its many characteristics, especially its ability to adapt to different climatic conditions and occupies the third position after wheat and rice in terms of crop area. Currently, maize is cultivated in more than 240 hectares of Iranian land (Gheţe et al., 2018). Super Sweet Corn is a monocotyledonous, annual, single plant of the family poaceae, which is widely used in agriculture and industry (Gheţe et al., 2018). Abiotic stresses affect different aspects of plant growth, such as reduction and delay in germination, decrease in development rate, decrease in plant organs growth, and decrease in plant life duration and finally decrease in dry matter production. Among abiotic stresses, drought stress is considered to be the most influential type of stress in the production of oil seeds in the world and can greatly reduce production on many arable lands. One of the primary effects of drought is the reduction of water content of plant tissues (Ghanbari et al., 2016). Nitrogen is one of the major nutrients in biomass determination and crop yield through impact on leaf area index (radiation intake) and photosynthetic capacity per leaf area unit (Compelo et al., 2019). Potassium in physiological applications including: carbohydrate metabolism or starch formation; protein metabolism; control and regulation of various essential minerals activities; Stomach and water play a key role (Tisdale et al. 2003). This study was carried out to investigate the effect of urea fertilizers combination with solopotass fertilizers on yield and yield components of Super Sweet Corn in different irrigation regimes.

This research was carried out as a factorial experiment in a randomized complete block design with three replications in Varamin Agricultural & Livestock Complex in 2016. Factorial combinations of three treatments of water deficit stress (15% (un-stressed control), 30% (moderate stress) and 45% (severe stress) of FC depletion), four nitrogen fertilizer rate (zero (un-fertilized control), 150, 200 and 250 kg.ha-1) from urea and four potassium fertilizer rate (zero (un-fertilized control), 100, 150 and 200 kg.ha-1) from potassium sulfate were considered. Drip irrigation (T-tape) was applied the row length in each experimental plot was 6 m, 50 cm apart. The distance between the plots and between the repetitions was 1 and 3.5 m, respectively. Plant to plant distance within each row was 8 cm. The irrigation schedules were based on soil moisture discharge of field capacity at the root zone of Super Sweet Corn with a depth of about 30 cm.

The results of this study showed that three-way interaction of irrigation time and chemical fertilizers was significant in leaf length and diameter, grain number, 1000 grain weight, photosynthesis rate and catalase enzyme. In moderate stress conditions, the highest grain yield was obtained from 150 kg urea and 200 kg solopotass, respectively. The highest photosynthesis rate and catalase activity were observed in the control treatment under severe stress conditions.

In general, it can be concluded that application of 150 kg urea and 200 kg solopotass increased 37.89 % grain yield compared to control under moderate stress conditions, respectively, that indicates the ability of chemical fertilizers to increase yield and yield components as well as increase photosynthesis rate under stress conditions and is highly effective in the emergence of resistance to super sweet maize plant and severe yield loss. Finally, application of 150 kg urea and 200 kg solopotass on the moderate stress conditions is recommended for optimum yield.