Thesis Abstract of AGS Students

Rice quality in relation to fertilizer management and market prices in yunnan

Chen Lijuan (1995)

This study was designed to investigate factors affecting rice quality and their impacts on market price as well as the effect of phosphorus (P) and zinc (Zn) on grain yield and qualities of rice. An informal survey including on-farm survey and market survey was undertaken in three selected sites namely Kunming, Dali, and Xishuangbanna of Yunnan province. P.R. China. In addition, market sampling was conducted to determine important rice quality characteristics. A total of sixty milled rice samples were collected from domestic markets of the three sites previously mentioned. The grain physiochemical properties of the milled rice samples were analyzed on the basis of Chinese Agricultural Ministry Standard for testing rice quality. A hedonic price model was further employed to quantify relationships between quality characteristics and market prices of rice.

Results indicated that rice quality was mainly determined by variety. Moreover, the biophysical conditions and crop management techniques also influenced rice qualities. In terms of consumption, consumers' preference for rice varied among regions. Normally, local ethnic consumers in the southern region (Xishuangbanna) prefer indica and glutinous rice. The consumers of northwestern region (Dali) and central region (Kunming) prefer japonica rice. In consumers' sense,

high quality rice refers to good taste, and/or with less brokens, slender grains, fewer chalkiness, higher translucency, and higher nutritional value. Market prices of milled rice showed significant difference among regions, rice sub-species (i.e. irrigated indica, irrigated japonica, and upland rice), and rice varieties. Rice varieties with high price (> 3.50 yuan/kg) were associated with their quality characteristics of aromatic (i.e. Diantun 502), low-to-medium amylose content (i.e. Dianrui 456, Dianlong 201, and Hunan softy rice), less brokens (i.e. Thai rice), and higher protein and Zn content (i.e. Babao black rice). In addition, the implicit price estimation demonstrated that: (1) The prices of rice paid by local consumers in all three regions was affected significantly by length, amylose content, and gel consistency of grain. (2) The significant price determinants of irrigated japonica along with upland japonica rice included grain length, amylose content, gel consistency, alkali spreading value, and protein content of grain. In particular, the nutritonal value in terms of protein and Zn content of upland rice became important price determinants. (3) In irrigated indica rice, the significant price determinants included proportion of whole grain in total milled rice.

P and Zn management are two common farmer practices in rice production in Yunnan. A field experiment was conducted on soil which was low in available P and Zn at Rice Research Institute of Yunnan Agricultural University, Kunming to determine the effects of Zn and P on grain yield and qualities of various rice varieties. The experimental design was a split-split plot which consisted of three factors, which were two levels of Zn application (0 and 5 kg Zn/ha) as the main plot, three levels of P application (60, 150, and 200 kg P₂O₅/ha) as the sub plot, and three japonica rice varieties namely Xunza 29, Hexi 35, and Yungeng 34 as the sub-sub plot.

Experimental results suggested that there was an advantage in applying Zn and P for improving grain yield, protein content in grain, total amount of Zn and protein content in grain, and head rice recovery of total brown rice. The major finding of the field experiment revealed that: (1) Application of P and Zn increased grain yield, but the responses to P and Zn were different among varieties. (2) Amylose content of grain was mainly determined by variety, however, it showed a slight

increase with Zn applied. (3) Protein content was generally enhanced by increasing amount of P application regardless applications of Zn and variety. In contrast, an increase in grain yield due to applying Zn resulted a reduction of protein content in grain. (4) Head rice recovery generally increased as increasing in level of P application, but slightly decreased with Zn applied. Ac- cordingly, head rice recovery was positively associated hardness of grain. (5) Varieties had various capabilities to absorb and translocate P and Zn into the seeds. At final harvest, Zn content of grain was negatively associated with grain yield.

Overall results of this research provided new insight into consumers' preference for rice quality characteristics as reflected in market prices and impact of variety and crop management in terms of Zn and P application on improvement of rice quality.

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