A Primary Study on the Output and Input of Phosphorus in 14 Crop Fields in the Haihe River Basin, North China
Jiang Gao-ming, Huang Yin-xiao, Lin Shun-hua, Han Rong-Zhuang, Gao Lei-Ming
Chin J Plan Ecolo. 1995, 19 (3):
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1. The average concentration of P in the tissues of the 14 crops of the Haihe River Basin was 0.127%, varying from 0.023% to 0.214%. The highest P concentration in different organs of the 14 crops was 0.419%, while the lowest was 0.019%.2. Of the 14 crops in the Haihe River Basin, Panicum miliaceum had the highest P output (removal in the harvested parts) from the soil pool, being 99.758±56.935kg·ha-1·a-1 followed by Zea mays and Gossypium hirsutum. Ipomoea batatas could be considered to be the greatest P contributor to the soil pool (the returning rate averaging 12.557kg·ha-1·a-1, but including the edible parts), followed by Zea mays and Arachis hypogaea. Most of the other crops contributed a very small amount of P to the soil, generally less than 2 kg·ha-1·a-1.3. The fruits of Zea mays, Panicum miliaceum, Arachis hypogaea, Gossypium hirsutum and some others, and the stems or stems plus leaves of Zea mays, Arachis hypogaea and Ipomoea batatas and so on were the main P output carriers. The low P input rates of most crops grown in the Haihe River Basin suggested that a largeamount of P was removed with the harvested parts.4. The P outputs in the corn fields of different subsidiary river basins of the Haihe River Basin were different, in the order. Daqing River Basin> Chaobai River Basin>Zhangwei River Basin>Haotuo River Basin>Yongding River Basin.5. Our results show that the P removal by harvested crop parts was 22 times of the P returned, suggesting that if the straw was not returned, growing Panicum miliaceum, Zea mays and Gossypium hirsutum would result in P losses of 99.758, 32.661 and 26.591 kg·ha-1·a-1 respectively. To maintain the soil fertility, P fertilization or returning straw to the field are recommended. The farmers, however, have only paid attention to P fertilization, but have ignored the straw-returning method that is considered to be a very effective way to recycle not only P, but also other essential elements as well.