Increased rate of potassium fertilizer at the time of heading enhances the quality of direct seeded rice

Abstract

Background: Potassium (K) is not easily assimilated into organic matter but helps to improve rice quality. Paddy yield and its quality depend on the correct time of fertilization and harvesting (days after flowering) in the field. Methods: Changes in the grain quality of (Oryza sativa L.) were studied in a field experiment over two dry seasons using three rates of muriate of potash (MOP; 60% K 2 O) as 12.5, 25 and 37.5 kg/ha applied at the time of heading (7 weeks after planting-WAP). Paddy samples were harvested during 25, 30 (control), 35 and 40 days after 50% flowering (DAFF). Grain yield and physico-chemical characteristics of grain were studied after harvesting. Results: The impact of seasons and treatments' interactions was not statistically significant (P > 0.05) and, hence, data were averaged over two seasons. Length, breadth, true density and bulk density of rice grains were the highest with 37.5 kg MOP/ha applied at heading and harvested at 30-35 DAFF. Crude protein (6.24%) and crude fat (2.61%) contents in grains were the highest when harvested at 40 DAFF and 35-40 DAFF, respectively. Amylose content decreased with increased MOP rates at the time of heading and delayed paddy harvest. The highest average paddy yield (APY; 6.85 t/ha), head rice yield (HRY; 65%) and total rice milling yield (TMY; 67%) were recorded with 37.5 kg MOP/ha applied at heading of rice plant and paddy harvested at 35 DAFF. The APY, HRY and TMY were also 13.8, 7.7 and 5.9% higher, respectively, compared to the control. Applying K fertilizer at a rate 50% more (18.75 kg K/ha) than the recommended rate at the time of heading (7 WAP) and harvesting paddy at optimum maturity (35 DAFF), which is 5 days later than the recommendation, increase the yield and grain quality of direct seeded rice. Harvesting later than 35 DAFF resulted in a 10.5% loss of HRY (P < 0.05). Conclusions: The present study showed that K fertilizer applied at the rate of 37.5 kg MOP/ha at the time of heading 50% higher than the recommended rate is the best among K fertilizer treatments to obtain the highest HRY.

Yield, Grain Quality, and Starch Physicochemical Properties of 2 Elite Thai Rice Cultivars Grown under Varying Production Systems and Soil Characteristics

“…Good soil condition includes the availability and movement of water and air in the soil as well as the existences of organic matter (OM), lime requirement (LR), and three major elements (i.e., nitrogen (N), phosphorous (P), and potassium (K)) throughout the plant growth stages [26,[28][29][30]. These are greatly necessary for growth and development of the rice plant, and eventually improve its yield and grain eating and cooking quality [23,26,28,31]. Not only the nutrient deficiency condition but also the nutrient toxicity condition owing to excessive supplies of nutrients can enhance the invasion of pathogen and insects [32,33].…”

Nitrogen sources affected the biosynthesis of 2-acetyl-1-pyrroline, cooked rice elongation and amylose content in rice

“…Previous studies have shown that the number of spikelets per panicle, percentage grain filling and grain weight, were all affected by different nitrogen fertilizer [46,47]. Similarly [20], demonstrated that, Potassium source applied as panicle fertilizer significantly increases the grain yield and quality by helping in translocation of photosynthetic products and other plant metabolites, thus contributing to improved grain quality. It has also been reported that higher K rates result in a stronger aroma, whiter and glassier appearance and lower softness in basmati rice [48].…”

“…Previous studies have shown that 2AP content varies depending not only on the planting site and environmental conditions but also on the plant, genotype, cultivar and even part of the plant [24,49,50]. Also, knowing the role that potassium plays for nitrogen like ensuring efficient utilization of N [51], the low values obtained in the treatment of KNO 3 would be due to the need that potassium has only facilitated the assimilation of nitrogen without bringing a significant impact in the increase of 2AP [20]. In addition, nitrogen sources such as urea H 2 NCONH 2 and NH 4 HCO 3 present a great advantage for the availability of nitrogen for plant growth and for 2AP biosynthesis [21].…”

“…[19] found that 2AP content in grains was increased with increasing nitrogen application. Field crops generally take up potassium (K) faster than nitrogen (N) or phosphorus (P), where K also plays an important role in ensuring efficient nitrogen use with an input of KNO 3 for example [20]. Thus the K input plays a role in many important regulatory processes in the plant such as the quality of the rice grain related to 2AP [20].…”

“…Field crops generally take up potassium (K) faster than nitrogen (N) or phosphorus (P), where K also plays an important role in ensuring efficient nitrogen use with an input of KNO 3 for example [20]. Thus the K input plays a role in many important regulatory processes in the plant such as the quality of the rice grain related to 2AP [20]. Ammonium bicarbonate (NH 4 HCO 3 ), Nitrate (NO 3 ), Urea (H 2 NCONH 2 ) and other compound fertilizers are important and can affect crop growth, yields and therefore quality through the known effect of nitrogen on 2AP [21,22].…”