Evaluation of yield and yield components of maize (Zea mays L.) under the influence of irrigation regimes and tillage systems

Maize (Zea mays L.) is ranked fourth among cereals in terms of area under cultivation and grain yield after wheat, barley and rice. Water scarcity or water stress is one of the most limiting factors in crop growth and crop yield, which reduces the average yield by 50% and even higher values. Water stress in corn through adverse effects on inoculation and grain filling, reduced plant photosynthesis, reduced amount of material grown and as a result of grain shrinkage, reduced leaf area and disrupting physiological processes, reduces the number of grains per ear, weight Thousands of seeds, bio-yield and grain yield. Conservation tillage is one of the inevitable methods of conservation agriculture by which the effect of water stress on plant growth and yield can be reduced. In agro-ecosystems, conservation tillage, while preserving and improving water resources and the environment, improves crop production and makes it sustainable. Since Iran is located in the arid and semi-arid region of the world and drought has a negative impact on the yield of its products, the study of water stress and strategies to deal with it is of particular importance; Therefore, the purpose of this study was to investigate the yield response and yield components of maize to tillage systems and irrigation regimes in Karaj.
 

In order to evaluate the effect of different tillage systems and irrigation regimes on corn yield, an experiment was conducted as split-plot in the form of randomized complete blocks with three replications in the research farm of the University of Tehran (longitude 35 degrees East, latitude 35 degrees and 48 Minute North) in 2016. The main factor in this experiment was tillage with two levels (no-tillage and conventional tillage) and the second factor was irrigation with three levels (without water stress, moderate water stress and severe water stress based on 75, 110 and 150 mm evaporation from Evaporation pan surface, respectively). Irrigation was done using plastic tapes (type) and the irrigation volume was controlled by the meter. Irrigation treatments were applied from the 4-leaf stage. The distance between the main, sub-factors and blocks (replicates) was 10, 2 and 10 meters, respectively, and there were six 10-meter planting lines within each experimental plot. Also, the distance between rows of corn in the plots was 75 cm and the distance between plants per row was 15.5 cm (density of 86,000 plants per hectare). To determine the water requirement, the Class A evaporation pan method was used and using daily meteorological data, Equations 1 and 2 were used:ETC = KC × ET0 = (Eq.  1) ET0 = K p × E pan  (Eq. 2) in them, ETc = Evapotranspiration of the desired crop (mm.day-1), KC= Plant coefficient, ET0= Reference evapotranspiration (mm.day-1), Kp= Plate coefficient (without unit), E pan= Evaporation of the pan (mm.day-1)

The results showed that the effect of tillage and tillage interaction at irrigation levels on any of the traits was not significant, but the effect of irrigation regimes on plant height, number of seeds per ear, 1000-seed weight, ear weight, grain yield, Biological yield, harvest index and water use efficiency were significant. The highest plant height was obtained in conditions without water stress (217 cm). Also, the highest number of seeds per ear was obtained under normal irrigation conditions, so that the application of severe stress reduced the number of seeds per ear by 26%. Severe water stress reduced the weight of 1000 seeds by 12%. Also, the weight of ear decreased by 38% compared to normal irrigation in severe stress and reached 151 g. The highest grain yield in normal irrigation was 12471 kg.ha-1, which severe stress reduced grain yield by almost 40%. A similar trend was observed in biological yield, with severe water stress reducing by 29%. In terms of water use efficiency, severe water stress increased it to 2.21 kg.m-3, which showed a growth of 31% compared to normal irrigation.

The results of this study showed that the tillage system had no significant effect on any of the traits, but water stress had a negative effect on all traits except water use efficiency, so that plant height, 1000-seed weight, Number of seeds per ear, ear weight, grain yield, biological yield and harvest index decreased sharply but water use efficiency increased compared to treatment without water stress. Based on the results of this study, corn irrigation based on 75 mm of evaporation from the evaporation pan surface in similar climatic conditions is recommended.