Consecutive Application Effects of Washed Rice Water on Plant Growth, Soil Chemical Properties, Nutrient Leaching, and Soil Bacterial Population on Three Different Soil Textures over Three Planting Cycles

Abstract

The benefits of washed rice water (WRW) as a plant fertilizer, particularly over a consecutive application period, are not well studied. An experiment was therefore carried out to determine: the continuous effects of applying unfermented (F0) and 3-day fermented (F3) WRW on the: (1) soil chemical properties, soil bacterial count, and the growth and plant nutrient content of a test crop, choy sum (Brassica chinensis var. parachinensis), grown on three contrasting soil textures (sandy clay loam, clay, and silt loam); (2) nutrient leaching losses from these three soils due to the continuous application of WRW; (3) crops’ improvement in water use, if any, in terms of its water productivity (WP) and water use efficiency (WUE); and (4) the relationship between soil bacterial count and plant growth parameters. The effects of F0 and F3 were compared with conventional NPK fertilizer and a control (only tap water; CON). Two factors, treatments and soil types, were used factorially in a randomized complete block design for three consecutive planting cycles. Results showed that NPK and F3 produced a significantly (p < 0.01) higher plant growth in terms of fresh and dry leaf weights and total leaf area by 5 to 61%, compared to that obtained in the other treatments. Furthermore, plants receiving either NPK or F3 had a significantly higher plant nutrient content (P, K, Ca, Mg, and Cu) in the third planting cycle. Clay soil treated with F3, NPK, and F0 had significantly higher NH4+, P, Ca, Mg, Zn, and B, by 19 to 152% relative to the other soils, irrespective of treatments. Soil nutrient leaching losses of P, K, Ca, Mg, Cu, Zn, and B decreased with successive planting cycles for all treatments. However, soils treated with either F3 or F0 experienced higher leaching of NH4+ and NO3− by 37 to 259% and 13 to 34%, respectively, relative to the NPK and CON. Plants treated with either NPK or F3 also had higher WP by 21 to 42% than the other treatments. For all the treatments, plants’ WUE increased with successive planting cycles; however, there was no significant difference between the treatments. F3 stimulated a significantly higher growth and yield of choy sum due to its nutrient and bacterial contents, and the continuous increase in plant growth with successive planting cycles indicated the carryover effects of the treatments, particularly by F3.

Combined benefits of fermented washed rice water and NPK mineral fertilizer on plant growth and soil fertility over three field planting cycles

“…No consistent pattern was observed in terms of increasing plant growth, nutrient content, nutrient uptake, or soil nutrient content in the subsequent planting cycles. These observations are in contrast to those reported by [ 19 , 21 ], who observed that the effects of WRW on the growth of choy sum and kangkung had amplified over time. During the first planting cycle, WRW-treated plants experienced lackluster growth that was only slightly or no better than that of the control plants that received only tap water.…”

“…Acknowledging the significance of WRW reuse in agriculture and recognizing the limitations of most existing studies, [ 19 ] recently conducted a comprehensive and scientifically rigorous investigation into WRW's use as a plant fertilizer. They found WRW contained, on average, in mg L −1 : 81 N, 16 NO 3 –N, 18.8 NH 4 –N, 1452 S, 65 P, 131 K, 24 Ca, 25 Mg, 0.18 Cu, 0.07 Zn, and 0.12 B.…”

“…[ [19] , [20] , [21] ] further tested the effects of three-day fermented WRW, along with NPK chemical fertilizer, on the growth of two commonly grown leafy vegetables, choy sum ( Brassica chinensis ) and kangkung ( Ipomoea reptans ), under rainshelter conditions. Their trials showed that the benefits of WRW had a carryover effect; that is, its effects intensified over time.…”

“…[ 2 , [19] , [20] , [21] ] concluded that WRW is useful as a plant fertilizer, particularly over the course of several planting cycles, and that WRW is akin to a sustainable liquid biofertilizer [ 22 ]. However, their trials were conducted under controlled conditions of a rain shelter.…”

Utilization Of Rice Waste Water on Biomass and Carotenoid Pigment Arthrospira platensis

“…Global demand for fresh water in 2025 is projected to increase by 55% (Park, 2013). The increase is due to climate change and an increase in world population, which prompted the United Nations to advocate for more effective water management (Paquin and Cosgrove, 2016), where wastewater is used and reused or recycled for other purposes, rather than being thrown away (Nabayi et al, 2022). The utilization of rice washing wastewater can be proven through research.…”