The effect of water and nitrogen deficiency stress during vegetative and reproductive periods on the growth and yield of two varieties of corn

To receive a master's degree in the field of agricultural-agricultural engineering

Abstract

In order to evaluate the effect of nitrogen and water deficit stress during vegetative and reproductive growth on the growth and yield of two varieties of corn, a factorial split-plot experiment in the form of a randomized complete block design with three replications in the research farm of Boalisina University in the agricultural year It was done in 2017. Nitrogen levels (100 and 200 kg/ha) and irrigation levels (dehydration stress at the 10-8 leaf stage, dehydration stress at the milky to pulpy stage and full irrigation) were factorially placed in the main plots and corn cultivars (Singlecross 500 and 647) were placed in the subplots. Maximum leaf area index, durability of leaf area index from tillering to maturity, durability of leaf area index, linear rate of crop growth, plant growth rate in flowering and in flowering per seed, plant growth rate in seed filling period, net absorption rate, biological yield, economic yield and harvest index, spud number after 10 leaves and seed pulp, water and light efficiency were measured. Also, yield components including number of cob rows, number of seeds per cob row, number of seeds per cob and seed weight were measured. The lowest values ??of the growth indices in the vegetative growth period were obtained with the consumption of 100 kg of nitrogen per hectare and water stress in the vegetative stage. In addition, it led to an increase in the time interval between planting and flowering and a decrease in the growth rate of the plant during flowering, and it continued as a decrease in the period of seed filling. The highest values ??of plant growth rate in flowering and plant growth rate in flowering per seed were obtained with the consumption of 200 kg/ha of nitrogen and both full irrigation and stress in reproductive stage. In addition, the highest value of the plant growth rate in the period of seed filling per seed in both cultivars studied was obtained with the consumption of 200 kg of nitrogen per hectare and water deficit stress in the vegetative stage. More seeds were obtained with the use of 200 kg of nitrogen per hectare and both full irrigation and drought stress in the reproductive stage, and singlecross 647 was superior to singlecross 500 in this trait. Consumption of 200 kg of nitrogen per hectare and full irrigation showed more seed weight than other levels of nitrogen consumption and irrigation. The highest efficiency of light consumption was obtained as 3.87 g/MJ in Single Cross 647 with 200 kg of nitrogen per hectare and full irrigation. The highest efficiency of water consumption was achieved with the consumption of 200 kg of nitrogen per hectare and water shortage stress in the reproductive stage. The highest grain yield belonged to the treatment of 200 kg of nitrogen per hectare with full irrigation. On the other hand, the consumption of 100 kg of nitrogen per hectare and water stress in the vegetative stage showed the lowest seed yield. Consumption of 200 kg of nitrogen per hectare and drought stress in the reproductive stage suffered the lowest yield reduction due to drought stress. The singlecross 500 cultivar had a higher performance than the singlecross 647 cultivar in all treatments, which was higher than the singlecross 647 due to its superiority in biological performance, seed weight and harvest index. light.

Introduction

Globally, 73% of all fresh water is used for irrigation, 21% and 5% are used by industry and domestic sector, respectively (Gonzalez [1], 1998). Access to water is one of the most important environmental factors that limit the production of crops. On a global scale, about half of the world's lands suffer from water shortages (Kramer and Boyer [2], 1995). Due to variations in water availability and transpiration demand from year to year, during a crop season, or during a day, plants may experience water stress due to water loss in the transpiration process. The duration of the deficiency may vary from hours to days. Stomatal closure in the middle of the day and reduced carbon dioxide uptake in response to high transpiration rates are common under field conditions (Monteith [3], 1995). Actual commercial production of major crops is on average 33% lower than potential production (Boyer, 1982). Among the various factors that can reduce the production of agricultural plants is the water stress of plants, which is caused by insufficient water supply (Venjura and Upchurch[4], 2002). Irrigation is a necessary and effective way to improve crop production. So, the increase in production is primarily attributed to the development of irrigated lands.Although only about 20% of the world's arable land is irrigated, it is estimated that this ratio accounts for 40% of the world's agricultural production (Boyer, 1982). Water scarcity is one of the most challenging issues at the global level. The effects of climate change, including the increase of heat waves and the decrease of rainfall in many parts of the world, especially in the mid-latitude region, have changed the seasonal availability and volume of water resources and aggravated the shortages (Marland[5] et al., 2003). Being located in the mid-latitude region, Iran is one of the dry and semi-arid regions of the world and has Mediterranean weather conditions. Crop production in such a situation relies on irrigation due to the lack of rainfall and its disproportionate distribution, and at the same time, the limitation of water resources is the most important limiting factor, especially for summer crops (Spaskhah and Khajeh Abdulahi, 2005). The agricultural sector's share of the country's total extracted water is 72 billion cubic meters (94 percent) (Fardad and Golkar, 2011). Also, out of a total of 37.5 million hectares of identified agricultural lands and 20 million hectares of lands susceptible to irrigation in the country, only 7.7 million hectares (21% of agricultural lands) are covered by irrigation (Norjo et al., 2015). The limitation of water resources has caused water to be considered as the most important production input (Hamzai et al., 2014). Water stress in corn cultivation may occur due to lack of water or problems in the irrigation system for water supply (Pandy [6] et al., 2000) or the simultaneous growth of corn with other crops (Lake et al., 2016), in many arid and semi-arid regions. Basically, corn is native to tropical regions, but due to the wide range of adaptability of medium and early cultivars, it can be cultivated in cold regions with a short growing season and obtain an economic crop (Kochaki and Sarmadanya, 2012). Proper management of nitrogen fertilizer is important for economic and environmental reasons. An insufficient amount of nitrogen fertilizer appears as a decrease in yield and low economic efficiency, while excessive fertilization has negative effects on surface and underground water resources, and also reduces the net economic efficiency. In addition, excessive fertilization leads to the release of nitrogen oxides as the main greenhouse gases (Kappi and Sedjo [7], 2007). The formation of yield in agricultural plants involves a set of processes that are in a time sequence. Murata [8] (1969) divides the formation of grain crops into three stages. In the first stage, photosynthetic organs and absorbing elements are formed. The second stage includes the formation of flowers and the container of yield, and in the final stage of plant growth, production, accumulation and transfer of the volume or content of the yield is done. These processes are related to each other in such a way that any type of environmental stress that limits one of them may affect the next part and ultimately the performance.

Given the importance of the high-consumption element nitrogen in corn production and the importance of irrigation in the cultivation of summer crops, determining the reaction of corn plants to drought stress and the amount of nitrogen element consumption is of particular importance. is The present study investigated the response of two corn hybrids to drought stress in vegetative and reproductive stages and nitrogen consumption amounts in Hamedan.

Physiol. 107:385–391.

Abstract

Effects of nitrogen levels (100 and 200 kg/ha) and irrigation levels (water deficit stress at 8-10 leaf stage, water deficit stress at milk till dough) ripening and full irrigation) on some characters and yield of two corn (Zea mays L.) cultivars (Single Cross 500 and 647) evaluated through conducting field experiment in research farm of Buali-Sina University. The experiment was established as a completely randomized block design in a factorial split arrangement with three replications in the 2008 growing season. Compounds of fertilizer and irrigation allocated to main plots and corn cultivars to the subplots