Effect of jajar legowo planting system on microclimate factors, growth, and rice yield

. Climate change, especially global warming, affects plant physiology and crop yields. Jajar Legowo (Jarwo) planting system, with the existing planting alleys that some farmers have applied, needs to be sufficiently identified for changes in microclimate factors, growth, and rice yield. This study aims to identify the microclimate factors, growth, and rice yield in this planting system. The research was designed through field experiments in rice fields with the Jarwo 2:1, 3:1, and 4:1 planting systems. The research variables included microclimate factors (temperature, humidity, and light intensity), rice growth, and yield. The results showed that the sunlight intercept in each Jarwo planting system was not different. The highest average temperature was recorded in the Jarwo 2:1 system and the lowest in the Jarwo 4:1. The highest average humidity was recorded in the Jarwo 4:1 system and the lowest in the Jarwo 2:1 system. The study's results noted no significant difference in the variables of plant height, total number of tillers, number of productive tillers, and grain weight per panicle. The observation of grain weight per clump Jarwo 3:1 is significantly different from Jarwo 4:1. The existence of alleys in the Jarwo planting system does not significantly affect plant growth and yield.


Introduction
Climate change impacts various aspects, one of which is agriculture.Climate change, especially global warming, causes changes in weather, temperature, and humidity, which will affect plant physiology [1][2][3].Rice, as the staple food of Indonesian society, is widely cultivated with various cultivation technologies, including the Jajar Legowo (Jarwo) planting system [4,5].There are several Jajar Legowo planting systems, namely 2:1, 3:1, 4:1, and 5:1.Research on this system includes observing the microclimate [6], as well as the effect of the microclimate on rice tillers and plant height where the number of tillers in the Jajar Legowo system is higher than that in the System of Rice Intensification (SRI) [7].In each of these systems, there is the potential for differences in the formed microclimate.Microclimate is a local climate condition that directly influences certain physical characteristics of the environment [4].
Several studies related to applying Jajar Legowo have been carried out.In previous studies, the microclimate parameters measured in the Jajar Legowo system were temperature, relative humidity, and sunlight intensity [6].This study observed various Jajar Legowo planting systems, namely 2:1, 3:1, 4:1, 5:1, and 6:1, compared to the conventional system as a control.This study concluded that several Jajar Legowo systems did not affect the microclimate in temperature, relative humidity, or sunlight intensity.This research aims to identify the effect of Jajar Legowo 2:1, 3:1, and 4:1 planting systems on microclimate factors, growth, and rice yields.

Methodology
This research was conducted in Nglangun Hamlet, Karanglo Village, Polanharjo District, Klaten Regency, Central Java, from October to December 2022.Geographically, the research area is at 7°36' 51.9"South Latitude, 110° 39' 32.4" East Latitude ± 200 masl.The research was conducted on a site of 1800 m 2 by planting local Klaten Menthik Wangi rice.The materials used in this study were Menthik Wangi rice seeds, meters, and cameras.The research was carried out by field experiments, with the Jajar Legowo treatment 2:1, 3:1, and 4:1.Each Jajar Legowo system uses a spacing of 25 cm x 12.5 cm with a Legowo width of 50 cm.The study was conducted on a single plot with an area of 600 m 2 for each plot with random placement of the plots.The total land area for the three Jajar Legowo systems is 1800 m 2 .
Microclimate observations used a lux meter, minimum-maximum thermometer, and thermohygrometer.Observations of air temperature and humidity were observed between 07.00 and 09.30 (Western Indonesia Time, WIB) using a thermohygrometer.Observations of air temperature and humidity under the canopy of each Jajar Legowo plot were carried out three times at different points.Light intensity was observed using a lux meter to measure the light intensity above and below the plant canopy.The light intercept on each plot is then calculated.
Plant growth observations were made once a week in each plot.Observations of temperature, humidity, and sunlight intensity, as well as observations of plant height, total tillers, number of productive tillers, grain weight per panicle, and grain weight per clump for each plot, were carried out in clumps on the edge of the Jajar Legowo alley and the middle clumps between the Jajar Legowo alley, 30 clumps each.Plant height was observed in 90 edge clumps and 60 middle clumps from each plot weekly.Observational data were analyzed descriptively with the T-test and displayed with a histogram analysis of each research variable.

Microclimatic observation
The lowest air temperature was obtained on the 3 rd week of observation at 29°C, while the highest was on the 11 th week at 37.5°C.The lowest air humidity in the 5 th week was 53.67%, and the highest in the 7 th week was 90%.Both observations can be seen in Figure 1.Microclimatic observations showed the highest average temperature in Jajar Legowo 2:1 and caused the average humidity in the Jajar Legowo planting system to be the lowest compared to other planting systems.Meanwhile, the lowest average temperature was found in the Jajar Legowo 4:1 planting system with the highest average humidity.This is due to the large number of Legowo alleys in the 2:1 planting system, so much sunlight enters the plant canopy.This condition is in accordance with previous research that the wider the Legowo distance will cause an increase in air temperature, lower humidity, and increase the intensity of sunlight [8].Light intercept is the percentage of sunlight that reaches the plant [9].Interception of light during the study period ranged from 70% to 95%.Observations of light interception showed that at the 9 th week of observation or the age of the plant around ten weeks after planting (WAP), there was an increase in light interception but tended to decrease closer to harvest.This is in accordance with previous research that the amount of radiation intercepted by plants increases with increasing age of the plant and decreases again before harvest [10].

Plant growth and yield
Based on the results of the T-test, plant height between Jajar Legowo was not significantly different, but Jajar Legowo 4:1 showed the highest average, i.e. 124.65 cm (see Figure 2).This is in accordance with research, which states that the plant height of the local variety Irkasuma Merah showed no significant difference in the treatment of the Jajar Legowo 2:1 and Jajar Legowo 4:1 planting systems [11].Different results were obtained by research where the planting system significantly affected plant height, where the Jajar Legowo 2:1 treatment had taller plants than the Jajar Legowo 4:1 and tiles (20x20cm) [12].The conditions that occurred in this study were thought to be caused by the metabolic rate in plants, which significantly determines plant growth during the vegetative phase.In this process, apart from being influenced by the cultivation techniques used, it is also influenced by the varieties of rice planted and the environmental conditions of the plantings.Plant growth in Jajar Legowo 4:1 was the highest compared to other Jajar Legowo systems.This is in accordance with two previous studies, which stated that plant height in applying Jajar Legowo 4:1 was higher than Jajar Legowo 2:1 and 3:1 [13,14].This growth was not only influenced by edge plants but also due to plant population density.In addition, the growth in Jajar Legowo 4:1 was higher, allegedly due to the condition of the plot closest to the water source, so plant growth was more fertile than other Jajar Legowo.
Based on the T-test between Jajar Legowo, the total number of tillers did not differ significantly.As seen in Figure 3, the highest number of tillers was in Jajar Legowo 4:1 and the least in Jajar Legowo 2:1.This is different from two previous studies, which stated that higher plants use more assimilate for the formation of stems and leaves than for the formation of tillers [13,15].In addition to the influence of population density, the formation of tillers is also influenced by water availability so that even though the plant growth is high, the number of tillers is also higher.Based on observations, the average number of productive tillers in edge clumps was 16.23, while the average total tiller was 16.62.This data shows that the percentage of productive offspring to the total number of offspring was 97.65%.Meanwhile, observations in the middle clump showed an average of 16.4 productive tillers and an average of 17.13 total tillers.From this data, the percentage of productive tillers in the total number of tillers in the middle clump was 95.74%.The number of productive tillers in each Jajar Legowo planting system in the edge and middle clumps based on the results of the T-test was not significantly different, and the comparison between Jajar Legowo was also not significantly different.The average number of productive tillers from each Jajar Legowo planting system was relatively the same, with the highest number of tillers in Jajar Legowo 3:1 (see Figure 4).Productive tillers are influenced not only by the capture of solar radiation by the plant canopy but also by environmental conditions, one of which is the availability of water and nutrients.The formation of productive tillers does not only depend on the number of tillers formed but can also be influenced by environmental factors [16].Other studies have also confirmed that rice plants have the potential to form productive tillers based on the number of tillers, but this is not always the case because tiller formation is also influenced by the environment [17].Tall plants use more assimilates for developing stems and leaves than for developing tillers [15].Apart from the influence of population density caused by the use of Jajar Legowo 4:1, the formation of tillers is also influenced by water availability.
The grain weight per panicle was observed just before harvest by taking observational samples from each Jajar Legowo plot of 30 clumps.The weight of grain per panicle in several planting systems of Jajar Legowo based on the T-test was not significantly different.Still, Jajar Legowo 4:1 tended to be the highest, namely 4.39 grams, compared to other Jajar Legowo.The grain weight per panicle is influenced by the amount of grain per panicle.The highest weight was obtained at Jajar Legowo 4:1, and the lowest was at Jajar Legowo 2:1 (see Figure 5).These results are in accordance with research that Jajar Legowo 2:1 has the lowest number of grains per panicle [14].Different results were obtained in other studies comparing Jajar Legowo 2:1 and 4:1, that the number of grains per panicle Jajar Legowo 2:1 was more than Jajar Legowo 4:1 [13].This difference in yield is thought to be influenced not only by environmental conditions but also by the type of variety planted.Although different results were obtained, the Jajar Legowo planting systems were generally not significantly different.
Based on the results of the T-test, there was no significant difference in grain weight per clump between the edge clumps and the middle clumps.As seen in Figure 6, there was a significant difference in grain weight per clump between Jajar Legowo 3:1 and Jajar Legowo 4:1 based on the results of the T-test.The highest grain weight per clump was in Jajar Legowo 4:1 of 59.39 grams, and the lowest was in Jajar Legowo 3:1 of 49.23 grams.These results are in accordance with research, which states that Jajar Legowo 4:1 gives the highest grain yield compared to Jajar Legowo 2:1, 6:1, and 8:1 [18].Other studies obtained different results; namely, the highest grain yield was obtained at Jajar Legowo 2:1 [13].This difference in yield is thought to be due to many factors affecting crop productivity.Although the Jajar Legowo system provides the potential for more optimal utilization of sunlight and weed control due to the presence of alleys, environmental factors such as water availability significantly affect rice growth and yield.Similar results were also found in the sorghum study, where a better microclimate resulted in higher yields [19].

Conclusion
Applying the Jajar Legowo planting system 2:1, 3:1, and 4:1 did not give a significant difference in the variables of plant height, total number of tillers, and number of productive tillers.However, in the parameter of grain weight per clump, there was a significant difference between the Jajar Legowo 3:1 and 4:1 planting systems.The Jajar Legowo 4:1 planting system gives the highest plant growth and grain yield.

Fig 3 .
Fig 3. Total number of tillers observation