april 2011 final

Philippine Journal of Crop Science (PJCS) April 2011, 36 (1):37-46 Copyright 2011, Crop Science Society of the Philippines

Agronomic Response of Lowland Rice PSB Rc 18 (Oryza sativa L.) to Different Water, Spacing and Nutrient Management Ruth O. Escasinas1* and Oscar B. Zamora2 1

Department of Agronomy and Soil Science, College of Agriculture, Visayas State University, Visca, Baybay, Leyte 6521-A, Philippines; 2 Crop Science Cluster, College of Agriculture, University of the Philippines Los Baños, College, Laguna 4031, Philippines; *Corresponding Author, [email protected] A field experiment was conducted for PSB Rc 18 in two cropping seasons at the experimental area of the Department of Agronomy and Soil Science, Visayas State University, Visca, Baybay, Leyte to examine the agronomic responses of lowland rice grown under different water, spacing and nutrient management. The wet season cropping was from 8 November 2007 to 29 February 2008 while the dry season cropping was from 14 April to 17 August 2008. Different sources of fertilizers were designated as the mainplot and plant spacing as the subplot nested within 2 water regimes i.e. continuous flooding (conventional) and no flooding (soil was saturated but not flooded). Lowland rice may not need continuous flooding in order to produce high grain yield. Yield of PSB Rc 18 under non flooded condition was significantly higher than under continuous flooding water management system by 12-15% with water saving of 52-53%. This is applicable in high rainfall areas such as in the Visayas State University. Reduced plant height was recorded under no flooding condition, a characteristic that imparts resistance to lodging even at high grain yield. Composted goat manure and compost mixture (G. sepium + goat manure + rice straw + carbonized rice hull) as organic fertilizers gave similar grain yield as inorganic fertilizer, implying that these materials are viable alternatives to expensive inorganic fertilizers. Plant spacing of 20 x 20 cm and 40 x 10 cm did not differ significantly in most agronomic characteristics as well as grain yield. However, in 20 x 20 cm spacing, transplanting and weeding were managed with less difficulty. Hence, 20 x 20 cm spacing is the appropriate distance of planting for optimum grain yield of PSB Rc 18 under organic production system. The treatment combination of no flooding, application of goat manure and closer spacing of 20 x 20 cm was the best combination that gave similar yield to PSB Rc 18 plants applied with inorganic fertilizer at 90-30-30 kg ha-1 NPK.

Keywords: agronomic response, lowland rice, nutrient management, root pulling resistance, spacing, water management

INTRODUCTION In the Philippines, rice production grew slowly for the past two decades (Sebastian et al. 2006). Yield growth has substantially declined from an average of 3.8% per annum in 1970 to 1986 to 0.9% yearly in 1986 to 2001. In contrast, population in the country is steadily growing at 2.5% annually. There is also an increasing trend in per capita rice consumption from 95 kg yr-1 in 1995 to 102 kg yr-1 in 2000. By 2009, it is projected that per capita rice consumption will increase to 121.8 kg yr-1 (University of Arkansas 2010). Therefore, the demand for rice has constantly outpaced the gains in production. As a result, net importation of rice has been increasing in the recent years. Production also became highly dependent on weather condition, which was highlighted by the El Niño phenomenon resulting in importation of more than 2 Mt in 1998. Among the rice producing regions in the country affected by these problems is Eastern Visayas (Region VIII). In 2007 and 2008, it ranked as the sixth

major rice producing region in the Philippines, producing 948,827 Mt in 2007 and 1,030,621 Mt in 2008 (DA-BAS 2009). In terms of area planted to rice, it ranked seventh with a total area of 276,537 ha. However, in terms of yield ha-1, it lagged behind Central Luzon, Cagayan Valley, Ilocos, Calabarzon, Northern Mindanao and Zamboanga Peninsula. These regions have average rice yields ranging from 3.79 to 4.52 Mt ha-1, while Eastern Visayas has only 3.73 Mt ha-1. To boost the rice production capacity of the region, there is a need to increase rice yield to more than 4.0 Mt ha-1. But it is not easy to attain this target considering the decreasing fertility of rice farms, the prevalence of pests and diseases and the ever increasing cost of commercial inputs, including inorganic fertilizers and chemical pesticides. Thus, there is an urgent need for the innovation of affordable and environment-friendly rice production technologies, such as organic agriculture technologies that suit local conditions that can be easily adopted by farmers.

High rice grain yield is achievable only with proper combination of variety, environment and agronomic practices (Yoshida 1977). Cultural manipulations of the growth of a rice crop in organic production system include changing the spacing recycling and use of organic fertilizer and alternative water management. Proper spacing results in better distribution of solar radiation and reduced phyllochron which consequently increase tillering resulting in higher yield. The use of organic fertilizer as alternative to chemical fertilizers would serve the dual purpose of minimizing pollution and utilizing manures for increasing soil productivity (Yadav and Lourduraj 2006). The rapid growth of population has resulted in significantly increased water demand. Agriculture is the largest consumer of water, particularly rice cultivation. With looming water scarcity, the sustainability, food production, and ecosystem services of rice fields are threatened, hence, there is a need to develop and disseminate water management practices that can help farmers cope with water scarcity in irrigated environments (Bouman et al. 2007). The field experiment was conducted to evaluate the agronomic responses of PSB Rc 18 under different water, spacing and nutrient management under VSU conditions. Specifically the experiment aimed to compare the performance of PSB Rc 18 under continuous flooding and no flooding water management system; to determine the appropriate distance of planting for optimum grain yield of lowland rice grown under organic production system and to evaluate the effects of different organic fertilizers on the yield and yield components of lowland rice.

MATERIALS AND METHODS Time, Place and Design of the Study This study was conducted at the experimental area of the Department of Agronomy and Soil Science, Visayas State University (VSU),Visca, Baybay, Leyte (100 N to 1240 E) during the wet and dry season. The wet season cropping was from 8 November 2007 to 29 February 2008 while the dry season cropping was from 14 April to 17 August 2008. The experiment was laid out in a nested design with complete blocks in 3 replications with organic fertilizers as the mainplot (F1- Composted goat manure, 3 t ha-1, F2-Compost mixture (Gliricidia sepium + goat manure + rice straw + carbonized rice hull, 1:1:1:1, 7 t ha-1, F3-Inorganic fertilizer at 90-3030 kg NPK, F4-Control, no fertilizer) and plant spacing (S1-20 cm x 20 cm, S2-40 cm x 10 cm, S3-40 cm x 40 cm) as the subplot nested within two water regimes i.e. continuous flooding (conventional) and no flooding or keeping the soil saturated but not flooded. 38

Cultural Management Practices Land Preparation The area was plowed and harrowed twice at weekly interval using hand tractor. After the last harrowing, the field was leveled and levees with appropriate height of 30.5 cm were constructed to avoid possible movement or contamination of nutrients from one plot to another. Each block was surrounded by a canal for irrigation and drainage. Seedlings Preparation and Transplanting PSB Rc 18 was used in this study since this variety is adapted to the locality and is commonly planted by the farmers in the area. Experience showed that this variety gave better performance even without pesticide application under VSU conditions (AB Escasinas 2006, personal communication). It is a medium maturing (123 DAS) lowland irrigated variety with erect leaf, high tillering capacity (14-17 productive tillers hill-1) and plant height of 102 cm. PSB Rc 18 is a high yielding variety with mean and maximum yields of 5.1 t ha-1 and 8.1 t ha-1, respectively (PhilRice 2007). PSB Rc 18 seeds were soaked in water for 24 hr and then incubated for 36 hr. Pre-germinated seeds were sown thinly and uniformly on raised seedbeds. To make pulling easier, the beds were kept saturated until about 3 d before transplanting. Ten-day old seedlings were transplanted with one plant hill-1 in an East to West row orientation following the spacing specified in the treatment. Single seedling was taken very gently between thumb and index finger at the base of the roots with some soil still attached to minimize transplanting shock. Missing hills were replanted 3-4 days after transplanting. Fertilizer Application Rice straw, goat manure, G. sepium and carbonized rice hull of equal volume were composted for 2 1/2 mo before the start of the experiment. Goat manure and compost mixture were analyzed for NPK, Zn and Cu at the Central Analytical Services Laboratory, PhilRootcrops Complex, VSU, Visca, Baybay, Leyte. Composted goat manure and compost mixture were incorporated into the soil two weeks before planting. The amount applied was based on its N content and recommended level of 90 kg N ha-1. For inorganic fertilizer treatment (F3), the basal application was 6030-30 kg ha -1. The remaining N (30 kg) was applied one month after planting. Water Management Continuous Flooding (Conventional, WM 1) - The field was continuously flooded up to 2 cm depth from 3 d after planting up to maximum tillering stage. Water level was increased to 5 cm at reproductive stage until 2 wk before harvest. To estimate the water applied a meter stick was set up at the center of the plot and

Rice response to different water, spacing and nutrient management

water level was recorded at 0800 h daily. The change in water storage was determined from the difference in initial reading and final reading. Rainfall and evaporation were gathered at the PAGASA station located 50 m away from the experimental site. No Flooding (WM 2) - The field was kept saturated by allowing entry of water but immediately drained to prevent flooding or submergence of the soil. Entry of water was allowed before the soil dried up or before it cracked. Water applied was estimated by using the continuity equation: Where: Q - Flow rate (m3 s-1) A - cross-sectional area of the inlet (m2) V - velocity of flow (m s-1) Pest Management A weed free condition was maintained throughout the duration of the experiment by using rotary hand weeder as well as manual weeding. For insect infestation, panyawan (Tinospora rumphii Boerl) + hot pepper + garlic + tobacco + soap extract was sprayed. Harvesting Harvesting was done when 90% of the grains had ripened. The harvested grains were cleaned and dried to about 14% moisture content. Data Gathered Agronomic Parameters 1. Plant Height (cm) was recorded from five randomly selected hills plot-1. The measurement was done from the ground level to the tip of the panicle. 2. Number of productive tiller per m2 was determined by counting all the tillers and the number of panicle-bearing tillers in one (1) m2. The number of tillers which bear no panicles or have less than five seeds per panicle was considered unproductive. 3. Panicle length (cm) was determined by getting the linear distance from the base of the panicle of the five sample plants used in the plant height measurement. 4. Filled spikelets per panicle was determined by manually counting all filled and unfilled spikelets of five (5) randomly selected panicles from each plot. 5. Grain weight per panicle (g) was taken from the same sample plants used for filled and unfilled spikelets count. 6. Weight of 1,000 seeds (g) was determined by weighing 1,000 seeds from each plot. Prior to measuring the weight, the moisture content was adjusted to 14%. 7. Grain yield (t ha-1) was taken from the harvestable area per plot of 8.16 m2. Grain RO Escasinas & OB Zamora

weight and moisture content were recorded. Yield was converted to kg ha-1 and adjusted to 14% MC and was then converted to t ha-1. 8. Root pulling resistance (RPR) was measured at flowering using a 100 kg spring balance to estimate the root strength (O’ Toole and Soemartono 1981). The base of the plant was tied using a jute rope attached to the spring balance. The highest value recorded in the spring balance when the plant is pulled from the soil is the RPR in kg. Soil Sampling and Analysis Soil samples were collected randomly from the experimental area within 0-20 cm depth before the conduct of the experiment. These samples were air dried and analyzed at the Soil Research Testing and Plant Analysis Laboratory, Department of Agronomy and Soil Science, VSU, Visca, Baybay, Leyte for the determination of the following soil chemical characteristics: pH, OM, total N and extractable P. The exchangeable K and cation exchange capacity (CEC) were analyzed at the Central Analytical Services Laboratory, PhilRootcrops Complex, VSU, Visca, Baybay, Leyte. For final soil analysis, soil samples were randomly collected from each treatment plot after harvest. Statistical Analysis The data were analyzed using the Statistical Analysis System (SAS ver 6.12). Mean comparison was done using Honestly Significant Difference (HSD) or Tukey’s test.

RESULTS AND DISCUSSION The soil used in this study had favorable organic matter content at 3.12% with moderate CEC at 22.10 me 100 g-1 and was therefore suitable for growth and development of the rice crop. Soil pH was acidic at 5.62 which is suitable for rice that grows in a wide range of pH varying from 4-8 (PCARRD 1986). Total N was low at 0.22%, potassium was moderate at 181.26 mg kg-1 but phosphorous was deficient at 8.32 mg kg-1. Plant Height Plants under no flooding condition were significantly shorter than those grown under continuous flooding in both cropping seasons (Table 1). Similar results were reported by Luikham (2001) and George et al. (2001) who reported that rice (var. Magat) had reduced plant height in aerobic soil; its height was substantially lower than its usual height of 1 m in flooded soil. This characteristic would likely contribute to lodging resistance even at high grain yield. Plants during the wet season fertilized with inorganic were significantly taller compared to the other treatments. This could be due to the immediate 39

Table 1. Plant height (cm) of lowland rice at maturity as affected by water management, fertilizer and plant spacing during wet (07-08) and dry (2008) seasons. Treatments Water Management Continuous Flooding (WM1) No Flooding (WM2) HSD 0.05 Fertilizer Composted goat manure (F1) Compost mixture (F2) Inorganic fertilizer (F3) Control (F4) HSD 0.05 Spacing 20 x 20 cm (S1) 40 x 10 cm (S2) 40 x 40 cm (S3) HSD 0.05

Wet Season

Dry Season

99.97 a 97.96 b 1.70

124.50 a 118.69 b 3.21

96.63 b 97.21 b 103.83 a 97.57 b 3.20 98.15 99.41 98.88 NS

123.27 ab 122.24 b 128.55 a 112.34 c 6.05 118.75 b 119.89 b 126.16 a 4.75

Means within a column followed by the same letters are not significantly different at 5% HSD.

release of nutrients by inorganic fertilizer and were made available for plant use at earlier period. In the dry season, the same treatment produced taller plants. However, this was statistically at par with those applied with goat manure in dry season only. Organic fertilizer released nutrients slowly hence its effect was observed in the dry season (2nd cropping) only. Unfertilized plants were the shortest. Plants at wider spacing (40 cm x 40 cm) were significantly taller compared to those plants at closer spacing during dry season only (Table 1). This could be explained by better access to nutrients, water and solar radiation that enhanced growth and development under this condition. This agrees with the findings of Vijayakumar et al. (2006) who reported that plants at wider spacing grew taller because of increased shoot:root ratio, ultimately the plants were able to get sufficient space to grow and the increased light transmission in the canopy leads to increased plant height. Panicle length Plant spacing, but not fertilizer and water management significantly affected panicle length during the wet season. Significant interaction between water management and fertilizer was likewise observed in the wet season. On the contrary, all the treatments significantly affected the panicle length during the dry season, compared to the control (Tables 2, 3, 4 and 5). Panicles of plants at closer spacing (20 cm x 20 cm and 40 cm x 10 cm) were shorter than those at wider spacing in both seasons (Table 4). Wider spacing resulted in longer panicles. This could be due to fewer plants per unit area and less competition for nutrients, water and solar radiation. Table 5 shows the effect of the interaction between water management and fertilizer on panicle length during the wet season. There was no difference in 40

panicle length in plants applied with goat manure and inorganic fertilizer as compared with the control. The shortest panicles were in plants applied with compost mixture grown under no flooding. This treatment was not significantly different from all other treatments with continuous flooding. During the dry season, plants applied with either organic or inorganic fertilizer, which were not significantly different from each other, gave longer panicles than the control plants (Table 3). Moreover, in the dry season, plants under continuous flooding had longer panicles than those under no flooding while in the wet season no significant difference was observed (Table 2). Productive Tillers per m2 Among the yield components, productive tillers are very important because the final yield is mainly a function of the number of panicle-bearing tillers per unit area (Baloch et al. 2006). The number of productive tillers was significantly influenced by water management, fertilizer and plant spacing (Tables 2, 3 and 4). There was no significant interaction among the treatments. Plants under no flooding condition had more productive tillers compared to plants under continuous flooding in both wet and dry seasons (Table 2). Increased tiller production under no flooding as reported by Vijayakamur at al. (2006) and Uphoff (2001) might be due to more availability of both oxygen and nitrogen in the root zone in the absence of continuous flooding. Plants applied with organic and inorganic fertilizers had higher number of productive tillers compared to the unfertilized plants (Table 3). Furthermore, closer spacing (20 cm x 20 cm and 40 cm x 10 cm) gave higher productive tillers m-2 compared to wider spacing in both seasons (Table 4). This could be due to more plant population per unit area under close spacing while the decrease in productive tiller m-2 at wider spacing (40 cm x 40 cm) was due to substantial decrease in population.


Table 2. Yield and yield components of lowland rice as affected by water management during the wet (07-08) and dry (2008) seasons.

Treatments Wet Season (07-08) Continuous flooding No flooding Dry Season (2008) Continuous flooding No flooding CV (%) (WS 07-08) CV (%) (DS 2008)

Panicle length (cm)

Number of productive tillers per m2

Number of filled spikelets per panicle

Weight of grains per panicle (g)

One thousand grain weight (g)

Grain yield (t ha-1)

24.18 a 24.35 a

258.54 b 289.55 a

127.29 b 141.30 a

3.23 b 3.65 a

25.74 a 26.45 a

4.45 b 5.12 a

29.05 a 28.56 b 4.24 10.15

236.63 b 275.45 a 23.69 21.42

134.94 a 132.59 a 7.63 18.41

3.40 a 3.34 a 6.50 12.60

25.02 a 24.58 a 10.51 4.87

4.23 b 4.74 a 11.26 4.99

Means within a column (per season) followed by the same letters are not significantly different at 5% level HSD.

Table 3. Yield and yield components of lowland rice as affected by fertilizer during the wet (07-08) and dry (2008) seasons.

Treatments

Wet season (07-08) Composted goat manure Compost mixture Inorganic Control Dry season (2008) Composted goat manure Compost mixture Inorganic Control CV (%) (WS 07-08) CV(%) (DS 2008)

Panicle length (cm)



Weight of grains panicle

Onethousand grain weight (g)


24.26 a 24.07 a 24.71 a 24.01 a

298.06 a 274.44 ab 289.10 a 234.58 b

132.08 a 128.84 a 142.98 a 133.27 a

3.50 ab 3.56 ab 3.61 a 3.30 b

26.82 a 26.70 a 25.27 a 25.56 a

5.27 a 4.93 a 5.35 a 3.59 b

29.16 a 29.21 a 29.64 a 27.20 b 3.91 5.17

279.18 a 271.88 ab 240.00 bc 234.10 c 23.62 23.28

134.04ab 132.06 b 144.41 a 124.53 b 3.24 13.87

3.35 ab 3.30 b 3.62 a 3.21 b 13.00 14.23

24.06 a 25.12 a 24.88 a 25.12 a 9.33 7.78

4.76 a 4.68 a 4.95 a 3.53 b 13.39 10.70


Table 4. Yield and yield components of lowland rice as affected by plant spacing during the wet (07-08) and dry (2008) seasons.

TREATMENTS Wet Season (07-08) 20 cm x 20 cm 40 cm x 10 cm 40 cm x 40 cm Dry Season (2008) 20 cm x 20 cm 40 cm x 10 cm 40 cm x 40 cm CV (%) (WS 07-08) CV (%) (DS 2008)

Panicle length (cm)



Weight of grains perpanicle (g)

One thousand grain weight (g)


23.87 b 24.10 b 24.82 a

318.13 a 323.35 a 180.26 b

127.18 b 125.88 b 149.82 a

3.31 b 3.18 b 3.23 a

25.98 a 25.78 a 26.53 a

5.49 a 5.53 a 3.34 b

28.17 b 28.49 b 29.74 a 3.44 3.49

288.75 a 285.42 a 193.96 b 17.11 15.23

125.36 b 124.14 b 151.78 a 11.68 9.64

3.23 b 3.15 b 3.72 a 9.62 10.13

25.14 a 24.35 aa 24.92 aa 8.44 8.10

4.48 a 4.71 a 3.74 b 9.99 9.25


Table 5. Panicle length (cm) of lowland rice as affected by water management and fertilizer interaction during the wet season (07-08). Panicle Length (cm) TREATMENTS Continuous flooding No flooding Composted goat manure Compost mixture Inorganic Control

23.73 b 24.42 ab 24.67 ab 23.89 ab

24.79 a 23.72 b 24.74 a 24.13 ab

Means followed by the same letters across water management and fertilizer are not significantly different at 5% HSD.

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Increased number of tillers per unit area with closer plant spacing was reported by Siddique et al. (1992), Vijayakamur et al. (2006), Baloch et al. (2002) and Yadao (2006). They attributed the increase to higher number of plants at closer spacing with lower number of tillers hill-1. Number of Filled Spikelets per Panicle Water management had significant difference but only during the wet season (Table 2). No flooding gave higher number of filled spikelets per panicle than those grown under conventional water management (continuous flooding). The interactions among different variables were not significant in both cropping seasons. There was a significant difference in the number of filled spikelets per panicle among fertilizer treatments in the dry season only (Table 3). Plants applied with inorganic fertilizer gave the highest filled spikelets which was not significantly different with those applied with goat manure. The lowest number of filled spikelets was in the unfertilized plants however, this was not significantly different to those applied with compost mixture. Significant differences in the number of spikelets per panicle were observed among the three spacing used in both seasons (Table 4). Higher number of filled spikelets per panicle was observed in plants grown at 40 cm x 40 cm than at 20 x 20 and 40 x 10 cm. This is because at wider spacing there is less competition among plants for light and other growth factors resulting in higher dry matter production, hence, higher filled spikelets per panicle. Weight of Grains per Panicle Significant difference in the weight of grains per panicle was observed among spacing in both cropping seasons (Table 4). Plants spaced at 40 cm x 40 cm produced significantly heavier grains compared to plants spaced at 20 cm x 20 and 40 cm x 10 cm,. This was due to more number of filled spikelets per panicle at wider spacing. The interaction between water management and fertilizer was significant during the wet season. Application of composted goat manure under no flooding condition resulted in heavier grains per panicle comparable to those applied with inorganic fertilizer while lighter grains was observed in the control plants under conventional water management (Table 6). Weight of 1,000 grains One thousand grain weight, an important yield determining component, is a genetic character least influenced by environment (Ashraf et al. 1999). There was significant interaction between water management and fertilizer during the wet season only. Higher 1000 grain weight was recorded in plants 42

applied with goat manure under no flooding conditions (Table 7). Lighter grains were recorded in the control plants grown under continuous flooding. Grain Yield Grain yield is a function of the interplay of various yield components such as number of productive tillers, spikelets per panicle and 1000-grain weight (Hassan et al. 2003). Highly significant differences among treatment means were observed due to water management, fertilizer and plant spacing in both cropping seasons. Likewise, there were significant interactions among the different variables. There was a highly significant interaction between fertilizer and spacing in both wet and dry seasons (Table 8 and 9). Grain yield of all fertilizer treated plots at closer spacing (20 cm x 20 cm and 40 cm x 10 cm) was significantly higher than those at wider spacing (40 x 40 cm). Similarly, the yield of the unfertilized plants was higher at closer spacing compared to wider spacing but was lower compared with fertilized plants. Control plants spaced at 40 x 40 cm had the lowest yield. Higher yield at closer spacing could be mainly attributed to the higher number of productive tillers per m due to relatively more number of plants per unit area (Table 4). Wider spacing on the other hand, consistently exhibited higher yield components such as panicle length, number of filled spikelets per panicle, and weight of grains per panicle due to less competition in growth factors hence, performed better as individual plant. The three-way interaction among water management, fertilizer and spacing was significant only during the dry season (Table 9). The treatment combination of no flooding, application of goat manure and closer spacing of 20 cm x 20 cm recorded the highest yield which was not significantly different from plants applied with inorganic fertilizer. This could be attributed to higher number of productive tillers under no flooding treatment during dry season (Table 2). Under non-flooded condition, there is abundant supply of oxygen to the root system. This improves metabolism and provides more energy for the growing plant. With more energy, roots are more developed and are more active in the uptake of nutrients. Furthermore, no flooding resulted in high root pulling resistance (Tables 10 and 11) which means better rooting in terms of depth and volume. More tillers mean greater number and density of roots and larger root system that supports more grain filling (Vallois et al. 2000). The grain yield in no flooding treatment was higher than that of the conventional water management during the wet and dry seasons (Table 2). This could be attributed to higher number of productive tillers m-2, filled spikelets per panicle and weight of grains per


Table 6. Weight of grains per panicle of lowland rice as affected by water management and fertilizer interaction during the wet season (07-08). Weight of Grains (g) Panicle-1 Continuous flooding No flooding

TREATMENT Composted goat manure Compost mixture Inorganic Control

3.22 ab 3.36 ab 3.32 ab 3.01 b

3.77 a 3.36 ab 3.90 a 3.57 ab

Means followed by the same letters across water management and fertilizer are not significantly different at 5% HSD.

Table 7. Thousand-grain weight of lowland rice as affected by water management and fertilizer interaction during the wet season (07-08). 1000-Grain Weight (g) Continuous flooding No flooding

TREATMENT Composted goat manure Compost mixture Inorganic Control

27.36 ab 25.86 abc 25.46 abc 24.28 c

27.77 a 26.11abc 25.08 bc 26.84 ab

Means followed by the same letters across water management and fertilizer are not significantly different 5% HSD.

Table 8. Grain yield of lowland rice as affected by fertilizer and spacing interaction during the wet season (07- 08).

Spacing

Composted goat manure

20 cm x 20 cm 40 cm x10 cm 40 cm x 40 cm

6.52 a 5.95 a 3.34 cd

Grain Yield (t ha-1) Compost mixture

Inorganic

5.54 a 5.97 a 3.27 cd

Control

6.18 a 5.80 a 4.07 bc

3.71 bc 4.40 b 2.67 d

Means followed by the same letters across fertilizer and spacing are not significantly different at 5% level HSD.

Table 9. Grain yield of lowland rice as affected by the interaction among water management and fertilizer and spacing during the dry season (2008).

Goat manure Continuous flooding 20 cm x 20 cm 40 cm x 10 cm 40 cm x 40 cm No Flooding 20 cm x 20 cm 40 cm x 10 cm 40 cm x 40 cm Mean

Grain Yield (t ha-1) Compost mixture

Inorganic

Control

Mean

4.68 bcde 4.99 abcde 3.22 fgh

4.96 abcde 4.18 cdefg 4.32 bcdef

5.31 abc 4.46 bcdef 3.77 defgh

3.71 efgh 4.55 bcdef 2.64 h

4.67 abc 4.54 bc 3.40 d

6.15 a 5.12 abcd 4.38 bcdef 4.76 a

5.19 abc 5.09 abcd 4.36 bcdef 4.68 a

6.08 a 5.58 ab 4.42 bcdef 4.94 a

3.82 defgh 3.72 efgh 2.84 gh 3.53 b

5.31 a 4.88 ab 4.00 cd

Means followed by the same letters across water management, fertilizer and spacing are not significantly different at 5% HSD.

Table 10. Root pulling resistance as affected by the interaction with water management and spacing at flowering during the wet season (07-08).

Spacing

Root Pulling Resistance (kg) Continuous flooding

20 cm x 20 cm

10.42 c

22.38 b

40 cm x 10 cm

12.04 c

24.21 b

40 cm x 40 cm

20.96 b

42.58 a

No flooding

Means followed by the same letter across water management and spacing are not significantly different at 5% level HSD.

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Table 11. Root pulling resistance as affected by the interaction of water management and spacing at flowering during the dry season (2008).

Spacing

Root Pulling Resistance (kg) Continuous flooding

No flooding

20 cm x 20 cm 40 cm x 10 cm 40 cm x 40 cm

18.62 d 21.50 d 42.33 b

35.92 c 36.88 c 53.08 a

Means followed by the same letters across water management and spacing are not significantly different at 5% level HSD.

panicle. This corroborates the results that continuous submergence is not essential for obtaining high rice yields (Guerra et al. 1998; Bhuiyan and Tuong 1995). In the dry season the number of filled spikelets and weight of grains per panicle were not significantly different hence, the increased in yield could be due mainly to greater number of productive tillers. This result conformed to the report of Baloch et al. (2006) that among the yield components, productive tillers are very important because the final yield is mainly a function of the number of panicles bearing tillers per unit area. The practice of keeping rice field not flooded but just keeping the soil saturated resulted in reduced water use by 52-53% and increased rice grain yield by 1215% (Table 12). Hatta (1967) reported that maintaining a very thin layer of water at saturated soil condition can reduce water applied to the field by about 40-70% compared with traditional practice of continuous shallow submergence without significant yield loss. Growing rice without flooding but just maintaining a wet soil condition from transplanting to maturity was more efficient in terms of water use than the conventional flooding system. During the wet and dry seasons, rice fields needs 491 and 938 liters of water to produce a kg of rice, respectively. However, under the conventional flooded condition, a kg of rice needs 1,210 and 2,201 liters of water during the wet and dry seasons, respectively (Table 13). This is very advantageous in areas where irrigation water is limited and rainfall is high. In a Type IV climate, such as at the Visayas State University, where the rainfall is high reaching an average of more than 300 mm during the conduct of the experiment and mean historical monthly rainfall of 254 mm for the past 32 years (Figure 1), rice productivity can be maintained at high level even without irrigation or impounding of water. On the other hand, the high yield due to the application of composted goat manure could be ascribed to the higher nutrient input including the trace elements (Cu and Zn) of composted goat manure than the compost mixture (Table 14). It contained 3.187% N, 0.448% P, 5.356% K, 28.50 ppm Cu, 224.45 ppm Zn and 29.726% OM. The higher nutrient content of goat manure especially nitrogen, as well as the gradual but continuous release of nutrients may have contributed to higher grain yield. Lowest yield was in 44

the treatment combination of continuous flooding, unfertilized plants and wider spacing of 40 cm x 40 cm. Root Pulling Resistance (kg) Root pulling resistance (RPR) at flowering was significantly affected by water management, fertilizer and spacing during the wet season but only by water management and spacing in the dry season. Significant interaction between water management and spacing on RPR was recorded in both cropping seasons (Tables 10 and 11). Highest root pulling resistance (RPR) was observed in the treatment combination of no flooding and wider spacing (40 cm x 40 cm). This was followed by no flooding and closer spacing (40 cm x 10 cm and 20 cm x 20 cm, respectively) which was similar with treatment combination of continuous flooding and wider spacing. The lowest was observed at treatment combination of continuous flooding and closer spacing. A similar trend was observed in the dry season cropping (Table 11). Root pulling resistance is influenced by soil type, soil moisture content at the time of measurement and operator’s skill during measurement (Marbun 2003). The significantly higher RPR at wider spacing was due to more tillers per hill resulting to more roots anchoring the soil. More tillers means greater number and density of roots. Hence, it is expected that plants at wider spacing are sturdier than those at closer spacing that experiences more intense competition, especially for solar radiation (both quality and quantity) that affects tiller production. Similar trend was observed in the dry season.

CONCLUSIONS Most agronomic characters were significantly affected by water management, fertilizer and spacing and some of their interactions. No flooding or just keeping the soil saturated but not flooded influenced most of the yield components of lowland rice. No flooding not only reduced water use by 52-53% but also increased the yield compared to continuous flooding treatment by 12-15% under VSU condition where rainfall is high. The use of composted goat manure and compost mixture as organic fertilizers in PSB RC 18 lowland


Table 12. Total amount of water used (m3 ha-1) throughout the growing season, yield and percent difference in water used and yield between two water management during wet (07-08) and dry (2008) seasons. Amount of water used (m3 ha-1)

Treatment Continuous Flooding No Flooding Difference (%)

Yield (t ha-1)

WS (07-08)

DS (2008)

WS (07-08)

DS (2008)

5,382.36 2,515.00 53

9,309.80 4,445.59 52

4.45 b 5.12 a 15

4.23 b 4.74 a 12

Means within a column followed by a common letter are not significantly different at 5% level HSD.

Table 13. Water productivity of lowland rice under continuous flooding and no flooding condition during the wet (07-08) and dry (2008) seasons at Visayas State University. Water Productivity (liter water per kg rice grain) Water productivity Irrigation Water productivity Irrigation+rainfall WS (07-08) (DS 2008) WS (07-08) (DS 2008) 1,210 2,201 4,561 5,500 491 938 3,404 3,841

Treatment Continuous Flooding No Flooding

Table 12. Chemical analysis of composted goat manure and compost mixture (goat manure + G. sepium + rice straw + carbonized rice hull) used as a source of fertilizer.

Organic Fertilizers

pH 1:2.5 ratio

Total N (%)

OM (%)

Total P (%)

Total K (%)

Total Cu (ppm)

Total Zn (ppm)

C/N

8.66

3.187

29.726

0.448

5.356

28.50

224.45

5:1

7.62

1.324

13.315

0.139

1.432

9.0

87.73

6:1

Goat manure* Compost mixture* (1:1:1:1) *Composted for 1.5 mo

optimum grain yield of PSB Rc 18 under organic production system and no flooding water management. Under VSU conditions, the treatment combination of no flooding, application of composted goat manure and closer spacing of 20 cm x 20 cm is the best combination for PSB Rc 18 comparable to plants applied with inorganic fertilizer at 90-30-30 kg ha-1 NPK. However, the economics of hauling and making goat compost needs to be considered. LITERATURE CITED

Figure 1. Mean monthly rainfall (mm) for the past 32 years (1976-2008) and actual rainfall (mm) during the conduct of the experiment rice could give yield comparable to inorganic fertilizer. These materials are viable alternatives to inorganic fertilizers. Closer spacing of 20 x 20 cm and 40 x10 cm give higher yield of PSB Rc 18 than 40 x 40 cm due to more number of plants per unit area. However for ease in transplanting and weeding operations, 20 cm x 20 cm is appropriate distance of planting for RO Escasinas & OB Zamora

Ashraf A, Khalid A, Ali K. 1999. Effect of seedling age and density on growth and yield of rice in saline soil. Pak J Biol Sci. 2(30):860 – 862. Baloch MS, Awa IU, Hassan G. 2006. Growth and yield of rice as affected by transplanting dates and seedling per hill under high temperature of Dera Ismail Khan, Pakistan. Journal of Zhejiang University Science. 7(7):572 – 579. Bhuiyan SI, Toung TP. 1995. Water use in rice production: Issues, research opportunities and policies implications. Paper presented at the Inter -Center Water Management Workshop, 29-30 September 1995 Colombo Sri Lanka: International Irrigation Management Institute. Geneva: World Health Organization. 45

Bouman BAM, Lampayan RM, Toung TP. 2007. Water management in irrigated rice: coping with water scarcity. Los Baños, Philippines: International Rice Research Institute. 54 p. [DA-BAS] Department of Agriculture-Bureau of Agricultural Statistics. 2009. Agri Performance. http://www.bas.gov.ph. (Accessed: 6 January 2009) George T, Magbanua R, Roder W, Van Keer K, Trebuil G, Reoma V. 2001. Upland rice response to phosphorus fertilization in Asia. Agron J. 93:1362-1370. Guerra LC, Bhuiyan SI, Toung TP, Barker R. 1998. Producing more rice with less water from irrigated systems. Swim Paper 5. Colombo (Sri Lanka), International Irrigation Management Institute. 26 p. Hatta S. 1967. Water consumption in paddy field and water saving rice culture in the tropical zone. Jpn. Trop. Agric. 11:106-112. Hassan G, Khan NU, Khan QN. 2003. Effect of transplanting date on the yield and yield components of different rice cultivars under high temperature of D. I. Khan. Sci. Khy. 16(2):179 – 137. Luikham K. 2001. Management of irrigation water and advanced method of nitrogen application on hybrid rice. [Dissertation] Tamil Nadu Agricultural University, Coimbatore. Marbun O. 2003. Agronomic performance of the system of rice intensification (SRI) and its acceptability to the farmers in Pila, Laguna, Philippines. [Ph.D. Dissertation] College, Laguna, Philippines: University of the Philippines Los Banos. 100 p. (Available at UPLB Library). [NSO-RP] National Statistics Office. 2009. Republic of the Philippines. Philippines in Figures. http:// www.census.gov.ph (Accessed: 16 October 2009). O’Toole JC, Soemartono C. 1981. Evaluation of a simple technique for characterizing rice root systems in relation to drought resistance. Euphytica. 30:283-290. [PCARRD] Philipine Council for Agriculture, Forestry and Natural Resources Research and Development. 1986. Environmental adaptation of crops. Book Series No. 37. PCARRD Foundation Inc. Los Banos, Laguna, Philippines. 289 p.

46

[PhilRice] Philippine Rice Research Institute. 2007. PalayCheck System for Irrigated Lowland Rice. PhilRice, Maligaya, Science City of Muñoz, Nueva Ecija. 90 p. Sebastian LS, Bordey FH, Gonzales LA. 2006. Embracing hybrid Rice: Impacts and Future Directions. SEARCA Agriculture & Development Discussion Paper Series No. 2006 -1. SEARCA, College, Los Baños, Laguna. 12 p. Siddiqui MRH, Lakpale R, Tripathi RS. 1999. Effect of spacing and fertilizers on medium duration rice (Oryza sativa) varieties. Ind. J. Agron. 44:310312. Uphoff N. 2001. Scientific issues raised by the system of rice intensification. A less water cultivation system. In: Hengsdijk, H. and Bindraban P. (editors). Water Saving Rice Production Systems. Proc. International Workshop on Water Saving Rice Production Systems. China, 69-82 pp. University of Arkansas. 2010. Per capita rice consumption of selected countries. www.uark.edu. (Accessed: 7 November 2010) Vallois P, Uphoff N, Collick A. 2000. Malagasy system of rice intensification. Http://www.simicro.mg/ ipnr/IPNRenDi.htm. 14 p. (accessed: 16 Dec. 2006) Vijayakamur M, Ramesh S, Prabhakaran NK, Subbian P, Chandrasekaran B. 2006. Influence of system of rice intensification (SRI) on growth characters, days to flowering, growth analysis and labour productivity of rice. Asian J of Plant Sci. 5(6):984 - 989. Yadao AC, Zamora OB. 2007. Comparison of the system of rice intensification and conventional production in Ilocos Norte, Philippines. Philipp J Crop Sci 32(2): 99-107.

Yadav BK, Lourduraj AC. 2006. Effect of organic manures and Panchagavya spray on yield attributes, yield and economics of rice (Oryza sativa L.). Crop Res. 31: 1-5. Yoshida S. 1977. Rice. In: Ecophysiology of Tropical Crops. Ed. by P. T. Alvim and T. T. Kozlowski. Academic Press, New York. 502 p.
