Requirement of rice ratoon to macroelements ( nitrogen and potassium) in Guilan paddyfields
2004
Kavoosi, Masoud | Rahimi Moghadam, Akbar | Ahmadipoor, Masoud | Safarpoor, Rahmatollah | Gafari, Yosef | Akbarzadeh, Ebrahim | Mohammadi, Mehrdad | Yahyazadeh, Gavad | Karimi, Mohammad | Mozaffari, Abed
Rice ratoon has considered as an effective approach to increase rice production and farmers income in the last few years. To satisfy high ratoon yield, recommendation of suitable nitrogen and potassium fertilizer rates is an essential factor. Therefore this study was conducted in Guilan paddyfields to determine suitable N and K fertilizer rates, during 2001- 2003. The experimental plots were treated with 0, 50, 100 and 150 kg N ha-1 from urea source, without or with 100 kg K2O ha-1 as KCL fertilizer in a RCB design with 3 replicates. The results have shown that in first year, treatments had no significant effects on grain yield of investigated paddyfields, expect in the cases of Astaneh and Rezvanshahr. The highest grain yield have obtained from N100 K100 and N50 K100 in Astaneh and Rezvanshahr, respectively. In second year, the treatments had significant effects on grain yield of two farms of Amlash, Lahijan, Razvanshahr and Astaneh experimental fields. The treatments of N50K100 in both two paddyfields of Amlash, N150K100 in Lahijan, N100K0 in Rezvanshahr, and N50K100 in Astaneh can be recommended as best fertilizer rates. In third year the treatments had significant effects on grain yield of all investigated paddyfields. The critical levels of soil total nitrogen was determined 0.177% for ratoon of rice crop (Hashemi variety) in investigated paddyfields with graphical cate- Nelson method. Therefore application of N fertilizers in paddy fields with total nitrogen content higher than 0.177% is not recommended. Kry words: Rice ratoon, Hashemi variety, soil total nitrogen, nitrogen and potassium fertilizer recommendation, nitrogen critical level.
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