Improving rice yield (Oryza sativa L.) and selected soil physicochemical properties using organic amendments under water-saving irrigation
Rice provides calories to more than half of the world's population, but consumes excessive water compared to other staple crops. To minimize this excess water usage alternate wetting and drying (AWD) irrigation practices are considered an efficient technique in which soil is intermittently i...
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| Format: | Thesis |
| Language: | English |
| Published: |
2022
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/104420/1/AHMAD%20NUMERY%20ASHFAQUL%20-%20IR.pdf |
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| Summary: | Rice provides calories to more than half of the world's population, but consumes
excessive water compared to other staple crops. To minimize this excess water usage
alternate wetting and drying (AWD) irrigation practices are considered an efficient
technique in which soil is intermittently irrigated. The addition of suitable organic
amendments could help to retain soil moisture and improve physicochemical
properties. In this context, four experiments were conducted to evaluate the effect of
organic amendments on soil physicochemical properties for improved rice yield under
water-saving irrigation. At first, an incubation study was conducted to evaluate the
incorporation of five selected organic amendments—as follows: rice husk biochar
(RHB), oil palm empty fruit bunch biochar (EFBB), compost, rice husk ash (RHA),
and oil palm bunch ash (PBA), with a control (no amendment) on soil moisture storage
and some chemical properties of soil. The soil was incubated with five amendments for
60 days and sampled at 15-day intervals. After completion of the incubation, RHB
(0.46 g g-1) and EFBB (0.45 g g-1) exhibited greater gravimetric water content
compared to the control (0.16 g g-1). PBA treatment produced maximum soil pH (6.95)
compared to its initial value (5.01). EFBB finally contributed to the highest total
carbon (7.82%) and nitrogen (0.44%). PBA showed the highest available phosphorus
(P) and exchangeable potassium (K). The second study investigated the effect of
water-saving irrigation with biochar and compost on the growth, yield, water
productivity of rice and physicochemical properties of soil. A glasshouse experiment
was executed with two irrigation regimes namely AWD and continuous flooding (CF)
and four treatments including three types of organic amendments namely RHB, EFBB,
and compost applied at 4% (weight/weight), and recommended fertilizer dose (RFD).
Under the AWD irrigation regimes, maximum grain was produced by RHB (241.12 g)
and the lowest in the RFD (210.15 g), whereas under the same organic amendments
both AWD and CF produced similar grain yields. RHB and EFBB with AWD
irrigation showed better water productivity (WP) (6.30 g L-1 and 5.80 g L-1,
respectively) over control treatment under CF (3.94 g L-1). Within the same irrigation
soil pH, cation exchange capacity, total carbon (C), and nitrogen (N) are enhanced by
biochar and compost incorporation. RHB and EFBB significantly reduced soil bulk
density up to 0.88 g cm-3 from 1.12 g cm-3 and enhanced porosity up to 58.7%
compared to RFD in CF irrigation. The next study was conducted to investigate the
effect of biochars on rice yield, fertilizer N use efficiency, and recovery under watersaving
irrigation by a 15N isotopic tracer. Two types of irrigation AWD and CF, and
four types of biochar treatments such as RHB with 15N urea, EFBB with 15N urea, 15N
urea alone, and control, were applied. About 4% reduced grain yield (193.89 g pot-1)
was achieved by the AWD regime over the CF (202.57 g pot-1, whereas RHB and
EFBB with 15N urea significantly increased rice yield (up to 8.8%) compared to 15N
urea alone. RHB and EFBB with 15N urea enhanced the fertilizer N recovery from 15N
urea (0.59 g g-1 and 0.61 g g-1, respectively), over 15N urea alone (0.49 g g-1).
Agronomic use efficiency and partial factor productivity of N were accelerated by
RHB (32.77 g g−1 and 73.14 g g−1, respectively) and EFBB (33.77 g g−1 and 74.14 g
g−1, respectively). The last experiment was conducted to assess the effect of biochar
combined with fertilizer on physiological response, water productivity and nutrient use
efficiency (NUE) of rice, and changes in biochemical properties of soil under AWD
irrigation. Two types of irrigation practices such as AWD and CF and four types of
fertilizer combinations namely T1: 25% RHB+75% of recommended fertilizer dose
(RFD), T2: 25% EFBB+75% of RFD, T3: 100% RFD, and T0: 0% biochar and
fertilizer were assigned. The AWD irrigation produced a sharply reduced grain yield
(210.58 g pot−1) compared to CF irrigation (218.04 g pot−1), whereas the biochar
combination treatments T1 and T2 produced greater yields (260.27 g pot−1 and 252.12
g pot−1, respectively), which were up to 12.5% higher than RFD (231.27 g pot−1).
Within AWD, irrigation water usage by T1 and T2 (98.50 Land 102.38 L, respectively)
was profoundly reduced by up to 28.8% over CF with T3 (138.25 L), with improved
WP. The main effect of biochar treatment T1 and T2 also increased photosynthesis rate
(21.31 and 20.950 μmol m−2s−1, respectively) compared to RFD (17.63 μmol m−2s−1),
in addition to boosted agronomic efficiency of N, P and K compared to RFD.
Nevertheless, T1 and T2 significantly enhanced the total carbon and nitrogen;
dehydrogenase and urease enzyme activities also increased in both irrigation regimes.
The results reveal that the integrated application of RHB and EFBB with the AWD
regime highly reduces irrigation water and improves NUE, WP, and soil quality with a
minimum yield penalty. Overall, the biochars not only boosted the soil C content and
nutrient availability but also increased moisture content with better soil porosity. The
addition of biochar in AWD irrigation is could be an efficient management system for
improved rice yield with improved WP. |
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