Influence of Organic and Inorganic Nitrogen on Grain Yield and Yield Components of Hybrid Rice in Northwestern Pakistan

Published Date
November 2016, Vol.23(6):326–333, doi:10.1016/j.rsci.2016.02.007
Open Access, Creative Commons license, Funding information

Author

• Amanullah ^,
 
• Hidayatullah

• Department of Agronomy, Faculty of Crop Production Sciences, The University of Agriculture, Peshawar 25130, Pakistan

Received 17 October 2015. Accepted 2 February 2016. Available online 16 November 2016. (Managing Editor: Fang Hongmin)

Abstract

Field experiments were conducted to assess the impact of various organic sources, inorganic nitrogen (N) and the different combinations of inorganic N (urea) + organic source on the yield components (YC) and grain yield (GY) of hybrid rice (Oryza sativaL., Pukhraj) under rice-wheat system. The experiments were conducted at Batkhela (Malakand), Northwestern Pakistan, in 2011 and 2012. Our results revealed that YC and GY ranked first for the hybrid rice when applied with sole inorganic N (urea), followed by the application of N in mixture (urea + organic sources), while the control plots (no N applied) ranked in the bottom. Among the six organic sources (three animal manures: poultry, sheep and cattle; three crop residues: onion, berseem and wheat), application of N in the form of poultry manure was superior in terms of higher YC and GY. When applying 120 kg/hm² N source, 75% N from urea + 25% N from organic source resulted in higher YC and GY in 2011, while applying 50% N from urea + 50% N from organic sources caused higher YC and GY in 2012. Therefore, the combined application of N sources in the form of urea + organic source can produce good performances in terms of higher YC and GY of rice under rice-wheat cropping system.

Keywords

rice

organic source

urea

nitrogen

yield component 

grain yield

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Nitrogen (N) is the most limiting nutrient of rice-wheat cropping system in Pakistan. Rice-wheat rotation is the most important cropping system in Pakistan (Amanullah and Inamullah, 2016a, b). Although considered as the backbone of food self-sufficiency in many parts of the world, the rice-wheat cropping system is facing a sustainability problem due to the extension of modern crop production system with the indiscriminate use of chemical fertilizers and pesticides (Prasad, 2005 and Hidaytullah, 2015). It causes some serious concerns, such as declined factor productivity (Biswas and Sharma, 2008, Patil, 2008 and Yadav, 2008), depletions of soil organic carbon and mineral nutrient contents (Prakash et al., 2008), etc.

Continuous use of chemical fertilizers without organic sources (OSs) will lead to gradual decline of organic matter content and change of native N status in the soils, which results in lower productivity in the rice-wheat system (Fu et al., 2014 and Pei et al., 2015). Rice provides 35%–60% of the dietary calories for more than three billion people in the world (Fageria, 2003). According to FAO (2001), the worldwide demand for milled rice is about 5.33 × 10⁸ t. Although rice is a heavy N consumer, the N fertilizer utilization efficiency in rice is very low under tropical conditions where it rarely exceeds 50% and usually ranges from 15% to 35% (de Dutta, 1986). N use efficiency is important for the economic sustainability of cropping systems (Fageria and Baligar, 2005 and Amanullah et al., 2010). Adequate N sources and rates are very important, which can not only increase yield but also reduce the cost of production and environmental pollution (Fageria et al., 2011). In the cropping system based on modern rice (Oryza sativa L.), low productivity (Biswas and Sharma, 2008, Patil, 2008and Yadav, 2008) and low soil fertility are the consequences of unbalanced use of N-fertilizers.

Pakistan is known as the 5th largest rice exporter, 10th biggest rice cultivator area and 14th leading rice producer in the world (Anonymous, 2014). Rice is one of the most important cereal crops in Northwestern Pakistan but its yield is very low there (from 1 633 kg/hm² in Lower Dir to 2 323 kg/hm² in Swat) (Amanullah, 2011). The growers in this area only apply urea to rice crop at a very low rate (50–60 kg/hm²) rather than the recommended rate of 120 kg/hm².

Organic manures are considered to produce higher crop productivity for sustainable agriculture (Suzuki, 1997 and Myint et al., 2010). Judicious use of chemical and organic fertilizers can improve rice plant growth, and increase rice yield and quality (Place et al., 1970, Fageria et al., 2006, Ahmad et al., 2008 and Masarirambi et al., 2012). According to Gately and Kelly (1987), the type of N fertilizer may affect the growth, yield and grain quality of rice. Nutrient-rich organic manures can be served as an effective substitute to reduce the costs of chemical fertilizers (Kumar and Mathew, 1994 and Masarirambi et al., 2012). In addition, soil organic manures can not only provide nutrients to the soil but also improve water holding capacity and assist the soil to maintain better aeration for seed germination and plant root development (Zia et al., 1998). The objective of this study was to investigate the impacts of different organic sources (animal manures vs. crop residues) in various combinations with inorganic nitrogen (urea) on grain yield and yield components of hybrid rice (Pukhraj) under rice-wheat cropping system in northwest Pakistan.

Materials and Methods

Field experiments were conducted to investigate the impacts of organic N sources (animal manures and crop residues) and inorganic N source (urea) on the yield components (YC) of hybrid rice Pukhraj including the number of panicles per plant, filled grains per panicle, 1000-grain weight and grain yield (GY). The experiments were carried out on farmer's field at Batkhela (34 37’ N and 71 58’17” E), Malakand Division, Pakistan, in 2011 and 2012. The soil was clay loam, slightly alkaline (pH = 7.3), non-saline (ECe = 1.02 dS/m), moderately calcareous in nature (CaCO₃ = 7.18%), low in soil fertility [containing less organic matter (0.71%), total N (0.51%), extractable P (5.24 mg/kg) and Zn (0.93 mg/kg)]. The details of 26 treatments are listed in Table 1. Organic sources were applied 30 d before transplanting while urea was applied in two equal splits, 50% at transplanting and 50% at 30 d after transplanting. A uniform basal dose of 60 kg/hm² P₂O₅ (as triple super phosphate) and 60 kg/hm² K₂O (as sulphate of potash) were applied uniformly to all plants. N sources were not applied to the control plots in both years. After the harvest of rice crop in October, wheat variety Siren-2010 was grown in November in both years as a subsequent crop.

Table 1. Treatments used in this study.

Treatment	Nitrogen from urea (%)	Nitrogen from organic sources (%)						Total nitrogen applied (kg/hm2)
		Cattle	Poultry	Sheep	Onion	Wheat	Berseem
T1	0	0	0	0	0	0	0	0
T2	100	0	0	0	0	0	0	120
T3	75	25	0	0	0	0	0	120
T4	75	0	25	0	0	0	0	120
T5	75	0	0	25	0	0	0	120
T6	75	0	0	0	25	0	0	120
T7	75	0	0	0	0	25	0	120
T8	75	0	0	0	0	0	25	120
T9	50	50	0	0	0	0	0	120
T10	50	0	50	0	0	0	0	120
T11	50	0	0	50	0	0	0	120
T12	50	0	0	0	50	0	0	120
T13	50	0	0	0	0	50	0	120
T14	50	0	0	0	0	0	50	120
T15	25	75	0	0	0	0	0	120
T16	25	0	75	0	0	0	0	120
T17	25	0	0	75	0	0	0	120
T18	25	0	0	0	75	0	0	120
T19	25	0	0	0	0	75	0	120
T20	25	0	0	0	0	0	75	120
T21	0	100	0	0	0	0	0	120
T22	0	0	100	0	0	0	0	120
T23	0	0	0	100	0	0	0	120
T24	0	0	0	0	100	0	0	120
T25	0	0	0	0	0	100	0	120
T26	0	0	0	0	0	0	100	120

The experiments were carried out in a simple randomized complete block design with four replications. The plot size was 12 m² (3 m × 4 m) with 300 plants per plot, and the plant to plant distance was 20 cm. All plots were separated by 30 cm ridges to stop the movement of water/nutrient. The number of panicles was counted using the average value of 10 plants (hills) per treatment. The number of filled grains was counted using the average value of 10 panicles selected from five different plants. One thousand grains were randomly selected for each treatment and weighed with three replications. After maturity, 2 m² of rice plants for each treatment were harvested, dried and weighed to calculate grain yield (kg/hm²).

Data were subjected to analysis of variance (ANOVA) according to the methods described for simple randomized complete block design combined over the years (Steel et al., 1996), and the means in different treatments were compared using the least significant difference (LSD) test (P ≤ 0.05). The Statistix 8.1 (Analytical Software, Tallahassee, USA) was used for the statistical analysis.

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