The effect of tree shading on soil temperature at Arabica coffee plantation (Coffea arabica L.)

Coffee is a group of plants that require partial light (C3), whose cultivation combines the use of shade trees and cultivated plants with the aim of increasing production and maintaining the microclimate around the cultivated plants. The shade provided by shade trees will have a significant effect on soil temperature and water content. The growth and development of a cultivated plant is strongly influenced by water content, on the other hand, water content also affects soil temperature. The optimal air temperature needed by Arabica coffee plants is 18-21°C, while the soil temperature suitable for Arabica coffee plants is 21°C. The research was needed to determine the effect of shade tree type on the soil temperature of Arabica coffee plants. This research was at the Koperasi Ribang Gayo Musara, Pantan Musara Village, Pegasing Subdistrict, Central Aceh District, Aceh Province. This research used a non-factorial randomized block design with five treatments and four replications. Treatments consisted of shade tree type on coffee plants were control/no shade, small lamtoro shade (Leucaena leucocephala ssp. leucocephala), big lamtoro shade (Leucaena leucocephala subsp. glabrata), banana shade (Musa paradisiaca L.), avocado shade (Persea americana Mill.). The results showed that the shade tree type had a significant effect on soil temperature at a depth of 0, 10, and 20 cm. Coffee plants that were shaded by avocado trees have better temperatures for coffee plants and can reduce soil temperature until they reach optimal temperatures.


Introduction
Coffee is a group of plants that require partial light (C3), whose cultivation combines the use of shade trees and cultivated plants with the aim of increasing production and maintaining the microclimate around the cultivated plants.The shade provided by shade trees will have a significant effect on soil temperature and water content.The growth and development of a cultivated plant is strongly influenced by water content, on the other hand, water content also affects soil temperature.The optimal air temperature needed by Arabica coffee plants is 18-21 0 C, while the soil temperature suitable for Arabica coffee plants is 21 0 C [1].The level of shade required by coffee plants varies according to the growth phase and conditions of the coffee plant.In the seedling phase or young age, the level of shade required is higher than in the adult phase or generative growth phase [2].Plant age and plant combinations are also thought to influence soil temperature fluctuations at different depths [3].Soil temperature is one factor in plant growth as important as water, air and nutrients.Soil temperature plays a role in 1297 (2024) 012029 IOP Publishing doi:10.1088/1755-1315/1297/1/012029 2 determining chemical reactions and soil microbial activity that can break down compounds Certain organics become nutrients and influence soil temperature seed germination and sprout growth [4].
The introduction of shade trees in agroforestry systems plays an important role in adapting coffee to shaded conditions to lower respiration rates and light compensation points.This plays a very important role in the growth and production of coffee plants in meeting their need for light as C3 plants.These changes will involve the ability of the species that make up agroforestry to adapt both morphologically and physiologically to various microclimatic conditions, especially the ability of coffee plants to adapt [5].
However, the effect of shade tree on coffee depends on the shade tree used.The use of different shade trees causes varied microclimatic conditions.Therefore, the research was needed to determine the effect of shade tree type on the soil temperature of Arabica coffee plants.

Materials and methods
This research was conducted at the Koperasi Ribang Gayo Musara, Pantan Musara Village, Pegasing Subdistrict, Central Aceh Distric, Aceh Province.Research implementation from June to August 2023.The tools of research were a hygrometer, anemometer, lux meter and thermometer.The experiment was done at Arabica coffee (Coffea arabica L.) plantation with type of shading trees as a research factor.

Figure 1. Soil temperature measurement
Soil temperature measurements were carried out three times a day, at morning (07.00-08.00WIB), noon (12.00-13.00WIB), and afternoon (17.00-18.00WIB).Soil temperature measurements were done every day for 8 weeks.Soil temperature measurements were carried out using a stick thermometer at a depth of 0, 10, and 20 cm from the top of the soil surface.

Shade tree effect on soil temperature at depth 0 cm
The shade tree type had a significant effect on soil temperature at a depth of 0 cm but was very fluctuating.From the 1 st to 4 th weeks, all treatments in the morning, noon and afternoon had not significant effect on soil temperature at a depth of 0 cm, but during the 5 th to 8 th weeks at the noon showed that the shade tree type had a significant effect on soil temperature at a depth of 0 cm (Table 1 and Fig. 2).
The soil temperature in the morning at a depth of 0 cm was very significantly different in the 7 th week with the lowest temperature found in the banana shade at 17.00 0 C, while the highest temperature was in the control (not shaded) at 17.92 0 C. The same condition also in the 8 th week, where the shade tree type had a very significant effect on soil temperature in the morning.The lowest soil temperature was obtained in the avocado shade with an average temperature of 16.79 0 C, while the highest temperature was in the control with an average temperature of 18.08 0 C. The measurement at the 8 th week, where the shade tree type had a significant effect on soil temperature in the noon.The lowest soil temperature was obtained in the avocado shade with an average temperature of 22.17 0 C, while the highest temperature was in the control with an average temperature of 25.04 0 C. Observations in the 5 th week during the day showed that coffee plants that were not shaded had an average soil temperature that was quite high (22.500 C).Meanwhile, shaded coffee plants had a temperature range of 21.38 0 C to 22.25 0 C. The best treatment was found in big lamtoro with a soil temperature was 21.38 0 C. Observations for the 5 th week in the afternoon showed that coffee plants with avocado shade had the lowest temperature (18.08 0 C).The highest soil temperature was found in the banana shade treatment (18.92 0 C).In the afternoon at 6 th and 7 th week the lowest soil temperature was found in the shade of the avocado.Even though in the 8 th week the soil temperature was the lowest in the small lamtoro and big lamtoro shade with a temperature of 19.73 0 C. The avocado shade had a very slight difference in soil temperature with temperature 19.74 0 C. The difference in soil temperature at a depth of 0 cm can be seen in Table 1.
Based on Table 1, it can be seen that during the day, coffee plants shaded by avocado trees have lower soil temperatures than other shaded trees.Avocado trees can provide nearly optimal soil temperatures for coffee plants, but it is feared that avocado trees can become rivals for the coffee plants themselves in finding nutrients.Apart from sunlight, there are many factors that affect soil temperature directly, such as local weather and climate, rainfall intensity.

Shade tree effect Soil temperature at depth 10 cm
The shade tree type had not significant effect on soil temperature at a depth of 10 cm except for a few weeks.The type of coffee plant shade has a significant effect on the average morning soil temperature in the 1 st week.The lowest average temperature can be found in coffee plants shaded by avocado plants (17.75 0 C), while the highest soil temperatures were found in coffee plants shaded by big lamtoro.
The average soil temperature in the afternoon of the 7 th week was significantly effect on all treatments.The lowest temperature was found in the avocado shade (19.92 0 C), while the highest temperature was found in the small lamtoro shade with a temperature of 20.79 0 C.
During the day of the 8 th week, the shade tree type had a very significant effect on soil temperature at a depth of 10 cm.The lowest air temperature was still found in coffee plants with avocado shade with an average temperature of 19.21 0 C. On the other hand, the highest temperature was found in coffee plants that were not shaded or control with 21.13 0 C.
In Figure 3, the average soil temperature at a depth of 10 cm was quite stable and did not fluctuate.The temperature that varies between weeks can be caused by local weather and climate.The type of shade itself did not show any significant effect on soil temperature at a depth of 10 cm.The difference in soil temperature at a depth of 10 cm can be seen in Table 2 and Figure 3.

Shade tree effect Soil temperature at depth 20 cm
At a depth of 20 cm, the soil temperature becomes more stable than the 0 cm and 10 cm depths.This was because stress and microclimate from the soil surface do not have a direct effect on soil temperature at this depth.The soil temperature will be more stable even though the surface temperature is very high.Areas that are not in contact with air temperature and direct sunlight, evaporation takes place slowly [6].[7].Futhermore, other factors are solar radiation, clouds and rainfall rain, wind and air humidity meanwhile internal factors, namely soil texture, structure and soil water content, organic matter content and earth color [8] are affected by the interaction of multiple factors, air temperature was found to be the main driving variable for the changes in soil temperatures [9].The shade tree type had not significant effect on soil temperature at a depth of 20 cm.The significant effect was found on the morning of the 6 th week.The lowest average soil temperature in the morning at a depth of 20 cm was found in coffee plants in the shade of small lamtoro with a temperature of 19.13 0 C, while the highest temperature was found in the shade of avocado (19.42 0 C).For the difference in average weekly temperature at a depth of 20 cm can be seen in Table 3 and Fig. 4. In general, the minimum temperature in the atmosphere occurs after sunrise, which is around 6 am in the morning, while the minimum temperature in the ground will experience a delay.For a soil depth of 5 cm the minimum temperature occurs at 8 am, for a depth of 10 cm occurs at 9 am, and for a depth of 20 cm occurs at 11 am.Heat that is conducted to the deeper soil layers will be absorbed by the soil layers through which it passes.As a result, the temperature of the soil in the lower layer will be lower than the temperature above it.
The maximum temperature in the atmosphere occurs at around 1 pm while the maximum temperature in the ground will occur after the time of maximum air temperature.The maximum soil temperature for a soil depth of 5 cm occurs after 2 pm, for a depth of 10 cm occurs at 3.30 pm and for a soil depth of 20 cm occurs at 6 pm or later [10].

Conclusions
The shade tree type has a significant effect on soil temperature at a depth of 0, 10, and 20 cm.Coffee plants that were shaded by avocado trees have better temperatures for coffee plants and can reduce soil temperature until they reach optimal temperatures.

Figure 3 .
Figure 3. Average Soil temperature at depth 10 cm

Figure 4 .
Figure 4. Average Soil temperature at depth 20 cm

Table 1 .
Average of soil temperature at 0 cm depth

Table 2 .
Average of soil temperature at 10 cm depth

Table 3 .
Average of soil temperature at 20 cm depth . Although soil temperatures