Study on Limit Factors of Soil for Orange Cultivation in Ham Yen District, Tuyen Quang Province

This study aims to evaluate the orange production situation and determine the limit factors of soil for orange cultivation in Ham Yen district, Tuyen Quang province. The methods of interviewing households by surveying, soil analysis and inheriting land research results in Ham Yen were used.The results showedthat the land area for orange cultivation in 2018 was 7,270ha, increased 3.25 times, yield increased 2.41times, and production increased 5.68 times, compared with 2010. Inorganic fertilizer applied to orange was 2-3 times higher than the recommendation. The number of households applied organic fertilizer to orange was low (15.56%) with the amount equalled to 1/10 of recommendation amount. Orange is cultivated mainly on Yellowish red soil on the metamorphic rock, Yellowish red soil on shale and Light yellow soil on the sandy rock. The limit factors of soil for orange cultivation in Ham Yen are high slopecausing erosion (>15, occupied 82% of households); soil reaction wasvery acid (pHKCl= 3.2-4.0, 82.2%); low organic matter content, poor available phosphorous and potassium, poor exchangeable Ca++in soil, especially Yellowish red soil on the metamorphic rock was missing exchangeable Mg++; low micronutrient (Cu and Zn content) in Yellowish red soil on the metamorphic rock.