Abstract
<p>A pot study was carried out to investigate the effects of rice husk biochar addition on rice growth performance and fertilizer nitrogen recovery. The biochar effect was studied by using <sup>15</sup>N labelled fertilizer urea (10 atom% <sup>15</sup>N), as isotopic tracer, until maximum tillering stage (75 days after sowing). Rice husk biochar (RHB) was applied at rates of 0, 5, 10 and 20 Mg ha<sup>-1</sup> and laid in randomized complete block design with four replications. The result showed that biochar application significantly improved soil chemical properties (pH, total C, total N, and available P) compared to control treatment. Biochar addition increased number of tiller and root dry matter weight up to 4% and 35%, respectively, compared to un-amended pot. Likewise, application of biochar significantly increased N, P and K uptake by 3%, 19% and 33%, respectively, as compared to the nutrient uptake from the control treatment. Biochar treatment had no significant impact on fertilizer nitrogen recovery in aboveground biomass, in the range of 41% and 42%, in comparison to the control. However, nitrogen fertilizer recovery in soil significantly increased by 47% over the control at application rate of 20 Mg ha<sup>-1</sup> RHB. Increased fertilizer N recovery in soil possibly reduced N losses to the environment from volatilization and denitrification processes. Total <sup>15</sup>N fertilizer recovery also found increase at highest application of RHB biochar with an increment of 16%. In general, addition of biochar appeared to enhance crop growth performance but its effect on fertilizer N recovery in plant requires further study up to maturity of rice plant.</p>
Highlights
The Malaysia population growth is estimated at 31.7 million persons in 2016 (Department of Statistics Malaysia, 2016)
The Rice husk biochar (RHB) rates was selected according to the study conducted by Masulili et al (2010) which used a similar source of RHB in rice cultivation on acid sulphate soil, Kalimantan, Indonesia
The highest soil pH value was observed in the pot treated with maximum biochar application rates, while the lowest value was recorded in the control pot
Summary
The Malaysia population growth is estimated at 31.7 million persons in 2016 (Department of Statistics Malaysia, 2016). The key factor which should be of concern is the efficient use of nitrogen (N) fertilizer such as urea in rice cultivation in Malaysia. According to Liu et al, (2010a), the global average N efficiency rate of 59% indicated that nearly two-fifths of N inputs were lost in ecosystems by various ways.High N fertilizer rates applied in rice cultivation are due to high losses of N (mainly gaseous losses) which was earlier reported to be more than 55% (Zhu and Chen 2002; Xu et al, 2012). As reported by Fageria and Baligar (2001), low fertilizer nitrogen use efficiency in lowland rice might due to N loss from leaching, volatilization, surface runoff and denitrification in the soil-flood water system. Roelcke et al (2004) and Zou et al (2009) reported that higher N fertilizer application at rates of over 200 kg N ha-1 were used for rice cultivation in eastern China so as to ensure high productivity. There has been increasing attention towards fertilizer N recovery, which is defined as the ratio of the N output or uptake by crops to fertilizer N input (Liu et al, 2010b; Qiao et al, 2012)
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