施用高量堆肥對水稻生長及養分吸收之影響

Abstract

摘要 本研究之目的在探討施用大量堆肥對水稻生長及養分吸收之影響，以做為有機農業肥培與土壤管理之參考。本試驗的堆肥施用量以高於一般田間耕作堆肥施用量的約十倍量添加，探討四種不同性質之堆肥 (豌豆稻殼堆肥 (PRC)、牛糞茶渣堆肥 (CTC)、豬糞稻殼堆肥 (HDR) 和豬糞鋸木屑堆肥 (HDS)) 肥效及殘效，對土壤性質、水稻生長、植物體氮組成、植體中養分吸收和重金屬含量之影響，並探討不同之處理在二種土壤中的養分變化和其釋出量。 孵育試驗用兩種土壤 (平鎮土壤和三坑子土壤)。在每100 mL 塑膠杯中裝入50克風乾土，土壤和堆肥 (6.7 g PRC、 6.6 g CTC、 6.3 g HDR 和 7.5 g HDS) 充分混合。另外有一種化學肥料 (N-P-K = 0.23-0.08-0.12 g kg-1) 處理及未施肥處理。堆肥施用量，以含氮濃度最低的豬糞鋸木屑堆肥為添加之基準 (土壤風乾重的15 %)，再換算其他種類堆肥的施用量，使得每種堆肥施入土壤的氮量皆相同。每個塑膠杯加水飽和後浸水1-2公分，杯面覆蓋鋁箔紙，放入25 oC恆溫箱中孵育16星期。其結果顯示，添加堆肥，使土壤pH值和電導度值皆提升。四種堆肥處理的差異，則因堆肥本身之pH值和電導度值而異。豌豆稻殼堆肥的添加，對土壤pH值的提升效應最顯著，而豬糞鋸木屑堆肥處理的土壤電導度值最高，在培育初期，其值大於4 dS m-1。在培育初期，土壤中銨氮濃度，因易分解的氮很快的礦化，在第一週即上升到最高值；隨著孵育時間增加，其濃度逐漸下降。以豌豆稻殼堆肥和豬糞稻殼堆肥處理之土壤銨氮濃度較高，可歸因於其堆肥中含較多易礦化的氮化合物。 盆栽水稻試驗之堆肥施用量與孵育試驗相同。一期作時，3 kg土壤與堆肥 (豌豆稻殼堆肥404 g、牛糞茶渣堆肥395 g、豬糞稻殼堆肥378 g和豬糞鋸木屑堆肥450 g) 充分混合後裝入1/5000 a Wagner的盆中；二期作時沿用一期作水稻收穫後的土壤，不再添加堆肥，藉以測定堆肥殘效性，但是化學肥料處理則添加與一期作相同量的氮和磷肥。每種處理有四重複，採逢機完全區集排列。結果顯示，在兩種土壤，施用大量堆肥，均使水田土壤之氧化還原電位急速下降至-200至-300 mV，平鎮土壤之未施肥或施化學肥料處理者之Eh則緩慢下降，而三坑子土壤卻與施堆肥的處理有相似的變化。四種堆肥處理中，以豬糞鋸木屑堆肥處理者，在栽培前期，其Eh值較高，顯示豬糞鋸木屑堆肥之分解比其他堆肥略慢。第一期作時，在平鎮土壤中，水稻生長初期，以牛糞茶渣堆肥和豬糞鋸木屑堆肥處理的水稻生長較佳，而豌豆稻殼堆肥和豬糞稻殼堆肥處理者，因土壤中銨態氮濃度較高，會抑制水稻的生長。成熟期時，稻草乾重以豌豆稻殼堆肥處理者較重，顯示豌豆稻殼堆肥因在抽穗期之後持續釋出多量的氮，而於生育後期使水稻繼續進行營養生長。在三坑子土壤，水稻生長初期，以化學肥料處理者之生長較佳，成熟期時，稻草乾重以豌豆稻殼堆肥處理者較重。第二期作時，在平鎮土壤中，水稻生長以豌豆稻殼堆肥、牛糞茶渣堆肥和豬糞稻殼堆肥之產量較高，顯示上述三種堆肥之殘效養分的釋出較足以供應水稻利用；而豬糞鋸木屑堆肥的殘餘效應最低，由於該堆肥產量為四種堆肥中最低者。在三坑子土壤，水稻生長以豌豆稻殼堆肥之產量顯著較高。 大量堆肥的施用，使土壤還原而增加二價錳與鐵，甚至溶解性鋁濃度的上升，但是水稻並不因此增加錳、鐵和鋁的吸收。反之，因有機物之存在，能與錳、鐵和鋁形成錯合物，而減少此三元素被水稻吸收，因而降低植體中錳、鐵和鋁的濃度。隨大量堆肥的添加而施入土壤的銅和鋅量會增加，但水稻植體中的銅和鋅 的濃度，與化學肥料處理者比較，因堆肥的存在而顯著減少。 關鍵字：水稻、堆肥、生長、養分吸收、氨毒。

Abstract The purpose of this study was to evaluate the effects and residual effects of high application rate of compost on the growth and nutrient uptake of rice plants. The application rate was about 10-fold as high as that in field. Four kinds of compost, (pea-rice hull compost (PRC), cattle dung-tea compost (CTC), hog dung-rice hull compost (HDR), and hog dung-sawdust compost (HDS), respectively) and two different soils (PC soil and SK soil) were used. A chemical fertilizer and a no fertilizer treatment were also contained. The soil chemical properties, rice plant growth, nutrient uptake at the different growth stages of rice plant were studied. The study was conducted through pot cultures. The effect of available nutrient concentrations in the two soils treated with the different composts were also studied through incubation. In the incubation test, each 50 gram of air-dried soil was mixed completely with appropriate amount of the four composts (6.7 g PRC; 6.6 g CTC; 6.3 g HDR and 7.5 g HDS) and chemical fertilizer (N-P-K =0.23-0.08-0.12 g kg-1) and then was placed in 100 mL beaker. The soil without any fertilizer was treated as control. After being submerged with deionized water, the soils were incubated at 25 oC for 16 weeks. The results indicated that the addition of compost to the soils increased the pH and electrical conductivity (EC) of the soils. The different effects on soil pH and EC among the four compost treatments were according to the differences in the pH and EC of the compost. The soil with addition of PRC compost had the highest pH and that of the HDS treatment had the highest EC. At the initial stage of incubation, EC of HDS treated soil reached to 4 dS m-1. The concentration of ammonium N in the soil reached the highest level after one or two weeks of incubation, and it declined gradually. The ammonium N concentrations of PRC and HDR treatments were higher than that of the other treatments, at the initial stage of incubation, and this was probably due to the high contents of easily mineralizable nitrogenous compounds. In the pot cultivation experiment of rice plants, the application rate of the composts was the same as that in the incubation study. Three kilograms of soil and appropriate amount of composts (PRC 404 g, CTC 395 g, HDR 378 g and HDS 450 g) were mixed thoroughly and packed into a 1/5000 a Wagner pot. After the harvesting of first crop, the same soils were used to study the residual effect without application of compost. However, the same rates of N and P fertilizers as applied in the first crop were applied in the second crop. All treatments were replicated four times and arranged in randomized complete block design. The nutrient concentrations of the root, leaf sheath, leaf blade, stalk, and grain were analyzed at different growth stages. The soil Eh and pH during the growth of rice plants were measured. The results showed that redox potential of the soil decreased rapidly to -200 ~-300 mV after submergence in the compost treatments. The Eh of the chemical fertilizer or no fertilizer treated-plots of PC soils decreased slowly, however, that of the SK soil decreased rapidly. At the early growth stage of rice plant, the soil of HDS treatment had a higher Eh than that of the other treatments. This indicated that biodegradation of HDS was less active than that of the other composts. In the PC soil, the dry matter yields of the CTC and HDS treated rice plants were higher than that of other treatments at the initial growth stage of the first crop. The dry matter yields of the PRC and HDR treated rice plants was lower than that of the chemical fertilizer treatment, owing to the ammonium N concentration in soil of the former treatments was higher than that of the latter. At the maturity stage, the straw yield of PRC treated rice plants was higher than that of the other treatments, and this could be attributed to the continuous release of N from the composts and beneficial to the new tiller formation at the ripening stage. In contrast to the PC soil, the dry matter yield of the chemical fertilizer treated rice plants in SK soil was higher than that of the first crop at the initial growth stage. At the maturity stage, the straw yield of the PRC treated rice plants was higher than that of the other treatments. In the second crop, the dry matter yields of PRC, CTC, and HDR treated rice plants in PC soil were higher than that of the other treatments, and this indicated that the nutrient release from the compost was enough to meet the growth demand of rice plants. However, in the SK soil, the dry matter yield of the PRC treated rice plants was relatively high, because the PRC compost still released a large amount of nitrogen and was beneficial to the growth of rice plants. The high application rate of composts resulted in the rapid soil reduction and increased the concentrations of Mn+2, ferrous ions as well as soluble aluminum ions dramtically. Nevertheless, the absorption of Mn+2, Fe+2, and Al+3 of the rice plants was not parallel to the concentrations of available Mn+2, Fe+2, and Al+3 in the soils. This could be attributed to the chelation effect of the organic matter with these metal ions. Similarly, analytical result also showed that the concentrations of Cu and Zn in the rice plants was significantly lower than that of the chemical fertilizer treated plots. Key words: rice plant, compost, growth, nutrient uptake, ammonia toxicity.