ผลของการใส่ปุ๋ยโบรอนที่ระยะการเจริญเติบโตแตกต่างกันต่อการดูดใช้โบรอนและการสร้างผลผลิตในข้าวพันธุ์ขาวดอกมะลิ 105 และปทุมธานี 1

Abstract

Rice production is not only dependent on the potential of rice variety, but environmental and management factors during cultivation also play a key role in enhancing yield and grain quality. Applying fertilizer is one of the promising strategies to encourage plant growth, development, and consequently productivity in rice crop cultivation, especially among macronutrient applications. However, micro-nutrients should also be given attention, though a very small portion is required, as they are necessary for plant growth and development, and it can cause yield declining under deficient and/or toxic conditions such as boron (B) due to boron deficiency affects to flower development in rice that can reduce yield production. Maintaining both quality and quantity of Thai rice is necessary to be investigated, especially for micronutrient management. However, the information of boron fertilizer applications on boron uptake efficiency that may affects to the productivity of Thai rice are rarely investigated compared with the other crops. This study was carried out in two mains experiments as in the following details. The experiment one was to evaluate the responses of boron uptake and productivity on soil boron fertilizer applications in Khao Dawk Mali 105 (KDML105) rice variety grown under different water managements. The experiment was arranged in 2×4 factorial in CRD with four independent replications. This experiment was conducted in the wet season in 2022 comprising of four boron fertilizer applications as 1) the control with no boron, 2) boron fertilizer application at tillering stage, 3) boron fertilizer application at flowering stage, and 4) boron fertilizer application two times at tillering and flowering stages cultivated under two different water management; 1) non-flooded and 2) flooded conditions. The results showed that grain yield was not responded to boron application in all treatments, but plants grown under flooded condition had 15% higher grain yield than non-flooded condition. The number of spikelets per panicle was increased by soil boron fertilizer application at flowering, and two times at tillering and flowering stages in flooded and non-flooded conditions resulted from increasing boron concentration in different plant parts and total boron uptake, even though it was not affected on grain yield. This study indicates that applying B fertilizer at flowering and two times at tillering and flowering stages improved number of spikelets per panicle and boron use efficiency of KDML105 rice variety in both water conditions, especially in the flooded condition, promotes soil boron availability and the total plant uptake. The appropriate management of boron fertilizer trends to be one of the ways to increase rice production if the unfilled fertilized grains can be completely filled. The second experiment was to evaluate the effects of boron fertilizer applications and rice variety on boron uptake and yield production. This study evaluated the appropriate growth stage for B fertilizer applications to improve production in rice. Two premium Thai rice varieties (Khao Dawk Mali 105; KDML105, and Pathum Thani 1; PTT1) were grown in the field experiment. Soil boron fertilizer was applied as (i) no boron application (control); (ii) boron application at tillering stage; (iii) boron application at flowering stage; and (iv) boron application two times at tillering and flowering stages with four independent replications. The results showed that grain yield was increased 25.0% when boron was applied at flowering stage and 53.6% when applied boron two times at tillering and flowering stages in KDML105 compared with grain yield at 2.8 t ha-1 in no boron application, but grain yield was not responded to boron application in PTT1. The increased grain yield in KDML105 was from the attribution of number of panicles per plant, number of tillers with no panicle emergences, and the percentage of filled grain resulted by higher boron concentration all plant parts and the total boron uptake when boron was applied particularly at flowering stage and two time at tillering and flowering stages as it was indicated by the sharp relationship between grain yield and boron concentration in all plant parts of KDML105. Interestingly, applying boron was found to increase the percentage of grain setting which was in correlation with the boron concentration in all plant parts. In addition, it also enhances the boron use efficiency in two rice varieties. It is interesting to investigate the mechanisms involving the function of boron in molecular level during fertilization, grain filling until maturity by splitting boron application at this period. The information would be very useful to improve grain productivity in rice cultivation, especially in the area where boron is in deficient condition.