Effect of available phosphorus in paddy soils on phosphorus uptake of rice

Relation between available phosphorus in 6 types of paddy soil in, Human Province and its uptake by rices was studied by³²P tracing. The result indicated that the P uptake by rices varied with available P content in the paddy soils. When the content was high, the rice absorbed more P nutrient from the soil and decreased the P uptake from the P fertilizer, which showed a poor contribution of the P fertilizer to the rice yield increase, and vice versa. The recovery of the P fertilizer varied with the soil types. Ranked the first was in paddy soils derived from lacustrine deposite but little rice yield increased. While in paddy soils derived from limestone, the yield greatly increased although the recovery of P fertilizer was the lowest. Rice absorbed P nutrient during its whole growth duration. No matter the different uptake amount due to the P supply by the different soils, rice plant generally had the greatest P nutrient uptake from tillering stage to elongation stage, and along with the rise of the rices dry matter, amount of P uptake was gradually increased but the P content in unit dry matter was tended to decrease.