有機質肥料之氮素礦化量預測

Abstract

為保育土壤及保護環境，以有機質肥料來代替大部份或全部化學肥料為現階段先進國家的主要農業發展新方向。本研究旨在探討有機肥料在輪作及土壤不同條件下之氮礦化及作物之利用性，繼以瞭解究竟可提供多少氮素以取代化學肥料。依據孵育期間堆肥之最高礦化氮量換算成堆肥施用量進行盆栽試驗，由本試驗植体吸收之氮、磷、鉀量反應出堆肥之肥效，有效性氮釋出量以化肥處理最高(392.3mg/kg)，豬糞堆肥次之(204.8mg/kg)，對照組最少(110.3mg/kg)。孵育期間之最高礦化氮百分率，豬糞堆肥和垃圾堆肥分別為122%及8.5%，而礦化潛能(Mineralization potential, No)則是豬糞堆肥(210mg/kg)＞垃圾堆肥(155mg/kg)＞空白處理(101mg/kg)；依據孵育期問堆肥之最高礦化氮百分率換算成堆肥施用量進行盆栽試驗，由植休吸收之氮、磷、鉀量反應出堆肥之肥效，其結果以全量豬糞堆肥者居首，分別是428,69,3及7629mg/pot，垃圾堆肥最差，特別是磷的供應。玉米盆栽試驗，於收穫期(R6)採土壤及植休樣品，分析其全氮、15N含量，藉以推算來自不同氮源之氮素含量。本試驗結果顯示來自化學肥料者約佔63~72%，豬糞堆肥者約佔16~20%，垃圾堆肥者約佔5~18%，而來自土壤之供氮能力，約27~40％不等。 It is well-known that the inadequate application of chemical fertilizers, especially Ammoniacal -N, is one of the main factors responsible for soil deterioration. In view of soil conservation and environmental protection the use of organic fertilizers substituting for chemical fertilizers, at least partly, has been suggested in industrialized countries. The objective of this paper was to study the mineralization potential of organic fertilizers and their contributions to nitrogen supply to soil and plant. There series of experiments were undertaken. (1) Labelled-N15 (2.5 atom %), 4g-N/pot and 1.2 g -N/pot for corn and rice respectively, was used in pot experiments to evaluate the contribution of organic fertilizers to nitrogen absorption of crops in a growing season. (2) Different organic fertilizers (hog manure, municipal refuse compost) were added into soil with water content remained at 60% of water holding capacity and incubated at 35¢XC for 16 weeks, soil exchangeable nitrogen was extracted with 2 M KC1 to estimate the mineralization potential of theses fertilizers. (3) According to the results of experiment (2), two organic fertilizers were used in a pot (3 Kg of soil) experiment to evaluate their contribution to corn growth. The results obtained from pot test of corn and incubation experiment may be summarized as follows: Under aerobic incubation condition, the release of available nitrogen from different treatments were in order of chemical fertilizer(392.3 mg/Kg), hog manure(204.8 mg/Kg) and control (110.3 mg/Kg). The highest N mineralization rate (%) of hog manure and trash compost were 12.2% and 8.5%, respectively. The mineralization potentials also had the same trend, e.g.hog manure (210mg/Kg) > trash compost (155 mg/Kg) > control (101 mg/Kg). Based on the maximum N mineralization rate (%), the composts application rate were calculated and used in corn pot test. The effect of compost application on nitrogen, phosphorus and potassium uptake by plant, hog manure treatment had best response on plant uptake, e.g.428.0, 69.3and 762.9 mg/pot for N,P,K, respectively. Trash compost treatment was the worst, especially in supply of phosphorus. Total N and 15N content of soil and plant were analyzed after harvest (R6 stage) in corn-rice pot indicated that nitrogen uptake of plant from chemical fertilizer, hog manure and trash compost treatments were under the range of 63-72%, 16-20% and 5-18%, respectively. However N obtained from soil originally due to their supplying capacities were ranged from 27% to 40%.