Abstract: In order to study the effect of cutting time and cutting height on yield and yield components of ratoon rice (Oryza sativa L.) Tarom langrody variety a field experiment was carried out in the field of Ghaemshahr Azad University in 2007. Experimental design was arranged in spilt plot in basis of Randomized Completely Block Design with four replications. Some agronomical traits such as numbers of effective tiller hill-1, panicle number m-2, total spikelet panicle-1, filled spikelets percentage, 1000 grains weight, grain and biological yield and harvest index were measured. Results showed that the effect of cutting time on number of effective tiller hill-1, panicle m-2, percent filled spikelet panicle-1, grain yield and harvest index were found statistically significant. Cutting height had a significant effect on number of tiller in hill, number of effective tiller in hill, number of panicle m-2, filled spikelet panicle-1 percentage, grain yield and harvest index. Interaction among cutting time and cutting height on number of tiller hill-1, number of effective tillers hill-1, number of panicle m-2 percent filled spikelet panicle-1 were significant. According to results cutting time at physiological maturity and also cutting in 40 cm cutting height from soil surface for the best grain yield of ratoon rice were recommended.
INTRODUCTION
Rice (Oryza sativa L.) is an important primary crop in the world. It is the staple food for more than two third of the world,s population. One of the several ways for increasing income of rice farmers is increasing of land utility. Reharvesting or ratoon cropping is one of the most important factors for increasing rice production and income of rice farmers. Ratoon cropping of rice is the practice of obtaining a second crop from the stubble of a previously harvested (main) crop (Turner and Junes, 1993). Enhances rice grain yields without increasing land area because it provides higher resource use efficiency per unit of land area and per unit of time (Bond et al., 2005). Ratooning of rice may be agronomically possible in climates when the crop season is too short to produce two rice crops but factors in influencing ratoon rice yields are not well understood. Ratoon affected by some factors like variety, planting space, cutting height, pest and diseases, weed, planting date of main plant, soil fertility, Total nonstructural carbohydrates, leaf agedness, heat degree, light radiation and growth regulators. Cutting height had different effect on ratoon yield. Some ratoon characteristics that affected by cutting height are grain yield, tillering and growth period length. For increase rice ratoon grain yield cutting height must be 0-50 cm from soil surface (Turner, 2007). Pirdashti et al. (2006) suggested that most ratoon yield was produced at 15 cm cutting height. Some reports showed that decreased in cutting height causes delaying in ratoon grain maturity (Rahman et al., 2007). Ting and Liu (1996) showed that cutting height at 5 to 15 cm had not significant effect on biological yield of rice ratoon in a experiment. Jason (2006) reported that cutting at appropriate height had positive effect on ratoon yield. Ting and Liu (1996) suggested that the most ratoon yield were produced in cutting height at 5 cm. the ratoon crop matures earlier, it has been reported that days to maturity of the ratoon crops are 65% less than the main crop. It requires 50-60% less labour. Require less water inputs, water use efficiency is high and crop use 60% less water than the main crop. The production cost is lower due savings in land preparation, transplanting or direct seeding and crop maintenance during early growth (Rahman et al., 2007).
For better yield of ratoon crop is possible by adopting appropriate management practices for main crop as well as to ratoon crop. These management practices include land preparation, adequate plant density and spacing, use of appropriate cultivars, water management, application adequate rate of fertilizers, appropriate height of cutting and control of diseases, insects and weeds (Wilson, 2001). Little specific information is available on the effect of many main crop management practices on ratoon crop performance. The main objective of this study was to evaluate the effect of main crop harvest cutting height and time on ratoon crop agronomic performance, yield and yield components.
MATERIALS AND METHODS
The experiment was conducted at the field of Ghaemshahr Azad University, Iran
(52°22’ N, 36°28’ E, altitude 28 m) in 2007. This experiment was laid
out in split plot in basis of Randomized Completely Block Design with four replications.
The soil total N and organic carbon contents were low. The available P and exchangeable
K contents are medium (Table 1). The plot size was 15 m2.
Main factor was cutting time in two levels (T1: the physiological
maturity and T2: 10 days after the physiological maturity) and minor
factor was cutting height from the soil surface in five levels (H1:
ground cutting, H2: 10, H3: 20, H4: 30 and
H5: 40 cm). All plots were fertilized with 100 kg P2O5
ha-1 and 100 kg K2O ha-1 before transplanting.
The applied nitrogenous fertilizer was 50 kg N ha-1 urea in ratoon
crop. Recommended agronomic all practices were followed and crop was harvested.
Six hills (excluding border hills) were randomly selected from each plot for
measure yield components. Grain yield was determined from harvest area of 5
m2 adjusting to 14% moisture content. All statistical tests were
done using the Statically Analysis System (SAS, 1996) and
mean valves were compared by Duncan Multiple Range test (DMRT).
| Table 1: | Physical and chemical properties of the top soil in the experimental field at Ghaemshahr Azad University |
RESULTS AND DISCUSSION
Cutting height: Results showed that cutting height had significant effect on number of tillers per hill and filled spikeletes percentage at 1% probability level also number of effective tillers hill-1, number of panicle m-2 and grain yield were influenced significantly by cutting height at 5% probability level. Most number of tillers hill-1, number of effective tillers hill-1 and grain yield were obtained in H5 cutting height. Most number of panicle m-2 (120.8) and filled spikelets percentage (79.82) were obtained in H3 and H4 cutting height, respectively. Pirdashti et al. (2006) showed that the highest number of tiller hill-1, highest number of effective tillers hill-1 and panicle m-2 were produced in 40 cm from soil surface cutting height. Cutting height had not significant effect on number of spikelet panicle-1, 1000 grain weight, grain and biological yield and harvest index.
Cutting time: The cutting time had a significant effect on number of effective tillers hill-1, panicle m-2, percent of filled spikekets, grain yield and harvest index at 0.01 probability level (Table 2). The highest number of effective tillers hill (8.66), panicle m-2 (138.6), percent of filling spikelets (82.59), grain yield (1294.1 kg ha-1) and harvest index (30.5) were obtained in harvesting physiological maturity (Table 3). This was perhaps due to decreased to delay cutting time and decreased in temperature cause reduce in yield and component yield. Cutting time had not significant effect on number of tillers hill-1, number spikelets per panicle, 1000 grain weight and biological yields. Results of this study are in agreement with those Thuamkham (2003) were obtained.
Interaction of cutting time and cutting height: Effect of cutting time
and cutting height on yield and components yield are presented in Table 4. The
highest number of tillers (17.33) and effective tillers hill-1 (10.23),
panicle m-2 (163.7) were obtained in first cutting time (physiological
maturity) in case of cutting height of 40 cm (Table 4). Some reports stated
that the highest number of tillers hill-1 and panicle m-2
were obtained in physiological maturity in cutting height of 40 cm.
| Table 2: | Mean squares of yield and yield components in ratoon rice (Tarom Langrodi Variety) |
df: Degree of freedom, CT: Cutting time, CH: Cutting height * and **: Significant at 5 and 1% a probability levels, respectively |
|
| Table 3: | Effects of cutting time and cutting height on the yield and yield components in ratoon rice (Tarom Langrodi Variety) |
| Means with similar letter(s) in each column are not significantly different at the 0.05 probability level according to Duncans Multiple Rang test, T1: Physiological maturity, T2: 10 day after physiological maturity, H1: Ground cutting, H2: 10 cm cutting height of soil surface, H3: 20 cm cutting height of soil surface, H4: 30 cm cutting height of soil surface, H5: 40 cm cutting height of soil surface | |
| Table 4: | Interaction effects of cutting time and cutting height on the yield and yield components in ratoon rice (Tarom Langrodi Variety) |
| T1: Physiological maturity, T2: 10 day after physiological maturity, H1: Ground cutting H2: 10 cm cutting height of soil surface, H3: 20 cm cutting height of soil surface, H4: 30 cm cutting height of soil surface, H5: 40 cm cutting height of soil surface, Means with similar letter(s) in each column are not significantly different at the 0.05 probability level according to Duncans Multiple Range test | |
The highest percent filled spikelets (88.87) and the lowest (61.70) were found in third cutting height in ground cutting height and second cutting time (20 day after physiological maturity) in cutting height of ground cutting, respectively (Table 4). Grain yield was not influenced significantly by interaction of cutting time and height. However the mean values showed that the highest grain yield (1587 kg ha-1) was observed in first cutting time in cutting height of 40 cm. The least grain yield (691.7 kg ha-1) was produced in two cutting time in for cutting height 30 cm.