ผลของการใส่ปุ๋ยโพแทสเซียมต่อผลผลิตและคุณภาพของเมล็ดข้าว พันธุ์ชัยนาท 1

Abstract

The large agriculture area is getting high risk of potassium (K) deficiency due to the intensive cultivation of the modern rice varieties with high yield, while K is applied into the crop lower than its uptake resulting in decreases potassium in soil, crop productivity and quality. Therefore, supplying K fertilizer into the cultivation soil has become important in rice crop to achieve the desirable productivity. However, there is a limit information on source and rate of K fertilizer that could be potentially applied into rice crop for approaching grain yield and quality. The objective of this study was to determine the effects of K fertilizer source and rates on yield and quality of Chai Nat 1 rice grain. The experiment was conducted at Mae Hia Agricultural Research, Demonstration and Training center, Faculty of Agriculture, Chiang Mai University during August 2018 to December 2019. The experiment was divided into two parts, field and greenhouse conditions. The field experiment was arranged in randomized completely block design (RCBD) with four replications. The four source of K were 1. Muriate of potash (MOP) 2. Polyhalite (POLY4) 3. MOP with ammonium sulfate (AS) 4. MOP with POLY4 and three rates of K consisted of 20, 40, and 60 K2O/ha. Potassium fertilizer was applied to the soil in all treatments except control. The greenhouse experiment was set in 4×2 factorial in completely randomized design (CRD) with 4 replications. The first factor was four source of K including MOP, POLY4, MOP with AS, and MOP with POLY4. The second factor was two water conditions including waterlogged and well-drained. Potassium fertilizer was applied at 60 kg K2O/ha to the soil in all treatments except control. The field experiment, grain yield, straw dry weight and yield components were not affected by sources and rates of K fertilizers but they were affected on the concentration and total uptake of rice plants. Applying all forms of K at 60 kg K2O/ha had K concentration in the straw and K uptake in the shoot higher than the control, ranging from 18 to 28% and from 33 to 47%, respectively. The greenhouse experiment, grain yield and straw dry weight were affected differently by K source and water conditions but no interaction effects between the factors was found. Applying K in MOP with AS increased grain yield and straw dry weight by 31% and 22%, respectively compared with the control, while no significant difference in the other K sources were found. Applying K in all treatments resulted in higher number of tillers per plant and panicles per plant than the control, except in MOP. Rice plants grown under waterlogged condition had 23% and 24% grain yield and straw dry weight higher than that of the well-drained treatment, respectively. Similarly, the higher culm length, number of tillers per plant, number of spikelets per panicle and grain weight were found in rice plants grown under the waterlogged condition. Grain yield was positive correlated with yield components in all parameters. The interaction between K sources and water conditions had significantly influenced on K concentrations and uptake in the stem of rice during booting stage. Applying all forms of K under waterlogged condition had K concentration and uptake higher than the control, ranging from 24 to 41% and from 45 to 47%, respectively except in MOP. In booting stage, the leaf K concentration of rice plants applied with MOP +AS and MOP + POLY4 had the highest K concentration which was 14% and 25% higher than the control, respectively and the total K uptake was 141 mg per plant. The water conditions had influenced on K concentration and uptake in different plant parts differently during plant growth. At maturity, rice plants grown under the waterlogged had K concentration in the stem, leaf, and flag leaf and total uptake higher than that of the well-drained condition. Grain yield was significantly positive correlated with K concentration in the leaf at booting stage, in the stem at 50% flowering stage and in the leaf and flag leaf at maturity. Increasing K concentration in the stem and leaf in all growth stages and in the flag leaf at maturity could increase grain yield in rice crop. However, no effect of K sources and water conditions on rice milling quality was found in this study. This study suggests that the productivity the rice variety Chai Nat 1 can be improved by growing under the waterlogged condition rather than the well-drained condition. Even though, applying K fertilizer into rice crop in the form of POLY4 resulted in the highest productivity, but the selection of K sources should also consider together with some other factors such as fertilizer cost and practically use in the fields. The K source of MOP should be applied into rice crop together with AS. However, the experiment should be confirmed by carrying on the similar experiment in the field condition and increasing number of varieties to obtain the responsive data among different rice varieties.