Abstract
To study the effects of different levels of nitrogen fertilizer on yield and yield components of cultivars of rainfed wheat a study was done in the crop year 2012-2013 as factorial in a randomized complete block design with 3 replications, in 2 research stations of Kohne Kand city in Bojnord and Shirvan dryland research station. The treatments of study contain cultivars of wheat in 4 levels (Rasad, Sabalan, Cross Sabalan and Azar 2) and 4 levels of nitrogen fertilizer (75, 50, 25 and 0 kilograms nitrogen per hectare). The results showed that the yield in Shirvan was significantly higher than that in Bojnoord. Moreover, the impact of cultivar and nitrogen on yield and yield components was significant in both regions and among different cultivars Azar 2 has the highest yield in both regions and the lowest yield was for cross Sabalsn in Shirvan and Sabalan in Bojnoord. Furthermore, yield increased by increasing the nitrogen in both regions but there was no significant difference between levels 50 and 75 kilograms per hectare. Among yield components except the number of spikes per square meter, others had a high correlation with yield.
Highlights
Wheat is one of the three cereals which has the most cultivated land in the world and dedicated to itself about one-third of the world’s arable land (Emam, 2007) [1]
Less than 31% of wheat production comes from rainfed farms (Ministry of Agriculture Statistics 2013) [3], and this reveals the importance of attention to rainfed wheat
On the other hand excessive use of nitrogen fertilizer in rainfed wheat leads to an increase in the growth period, production of more vegetative organs and decreases of grain yield, increase of the number of infertile grains and decrease of harvest index (Basso & Ritchie, 2005 [11]; Fischer, 1973 [15])
Summary
Wheat is one of the three cereals which has the most cultivated land in the world and dedicated to itself about one-third of the world’s arable land (Emam, 2007) [1]. Wheat production in arid and semi-arid areas largely depends on nitrogen management In these areas, due to the low soil organic matter, nitrogen is the most important limiting element of yield. Due to the low soil organic matter, nitrogen is the most important limiting element of yield Nitrogen mineralization in these areas is not sufficient for the needs of cereals and the use of appropriate amounts of nitrogen fertilizer to increase yield in these areas is essential (Ryan, 2002 [13]; Ryan et al, 2008 [14]). On the other hand excessive use of nitrogen fertilizer in rainfed wheat leads to an increase in the growth period, production of more vegetative organs and decreases of grain yield, increase of the number of infertile grains and decrease of harvest index (Basso & Ritchie, 2005 [11]; Fischer, 1973 [15]). Determining the appropriate level of nitrogen in dry lands which causes the maximum yield has particular importance in dryland areas
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