Introduction
The development of dry land agriculture in Indonesia has enormous hopes in realizing resilient agriculture in the future considering the potential and land area is much larger than wet land. Corn is an agricultural commodity that is needed in quite large quantities, so it is not surprising that the government has decided that corn is an imported commodity. It is estimated that more than 58% of domestic corn needs are used for feed, while only around 30% is used for food, and the rest is for other industrial needs and seeds [1] One of the determining factors in the availability of corn is the readiness of the land for cultivation.
Evaluation of land suitability is very necessary for planning productive and sustainable land use. The use of computer-based technology to support planning is increasingly necessary to analyze, manipulate, and present information in tabular and spatial form. Create a model that provides a description, explanation, and estimate of a factual condition. [2] One technology for evaluation is a methodGIS (Geographic Information System), through GIS, can make it easier to match the level of suitability according to the growing requirements of corn plants. Land evaluation is the process of assessing the potential of land for certain land uses ([3] and evaluating a diversity of factors Land evaluation has an important role in the potential for agricultural efficiency and sustainable land use [4]. Inappropriate land use, apart from causing land damage, can also cause socio-economic problems, and can even destroy a previously existing culture. On the other hand, appropriate land use is the first step to support sustainable land conservation programs.
Tolitoli Regency with a land use area of 772,323 Ha (14 611 paddy fields and 757 712 Ha non-rice fields) [5]. In connection with this, research was conducted on evaluating land suitability for corn crops in Basi Dondo District, Tolitoli Regency. This research aims to evaluate the level of land suitability for corn crops in Basi Dondo District, Tolitoli Regency.
Methodology
The method used in this research is 2 things, namely the interview method and sampling using the purposive sampling method, which is based on the needs and objectives of making maps and land suitability analysis which is used to obtain representative elements of data on each land unit using GIS ( Geography Information System).
Data retrieval
To collect primary and secondary data, several data collection techniques were used, namely:
1. preparation and creation of work maps
2. Field survey
3. Carry out an inventory of potential resource data and information.
4. Analyze soil samples in the laboratory
5. Prepare a map of potential resources, opportunities, and regional development areas.
6. Data management and report preparation
Activities carried out at this preparation stage are arranging field surveys, collecting secondary data (both numerical data and spatial data or base maps) related to the implementation of the study, providing tools, materials, and plans for placing observation and collecting soil samples and area coverage. The base map is used as a guide in determining the boundaries of the mapping planning area and as a guide for determining observation points and taking soil samples because the map produced from this study is classified as a detailed scale.
The reference sources for collecting data are: Administrative maps, land cover maps, soil maps, slope maps, rainfall maps, and climate maps. Other data required for land suitability analysis is in the form of physical field data to obtain the results of soil chemical analysis, both intact soil and incomplete soil, using a hoe, soil drill, and sample ring.
Data analysis
Analysis of Soil Physical and Chemical Properties
Analysis of soil samples/samples was carried out at the Soil Laboratory, Faculty of Agriculture, Tadulako University, Palu, namely to determine the texture (clay, sand, and dust), while soil chemistry consisted of macro and micronutrients: Nitrogen (N Total), Phosphorus (P2O5), Potassium (K2O), Soil acidity (pH), Cation Exchange Capacity (CEC) and Organic C [6].
GIS analysis
GIS analysis is using various types of maps to view or match fields or areas that will be research objects according to certain objectives [7]. Some of the map attributes are overlaid to make it easier to determine land map units or land units because Each land unit has its properties and characteristics ([8]
Land Suitability Evaluation
The method used in evaluating land suitability is the limiting factor method, namely, each land quality is arranged sequentially from the best (lightest limiting factor) to the worst (the most severe limiting factor), and each land quality is arranged in a criteria table.
The optimum land quality for plant needs or land use is the limit for the most suitable land suitability class (S1). Meanwhile, land quality that is below optimum is the limit of the land suitability class between the quite suitable class (S2), and/or marginally suitable (S3). Outside these limits are lands that are physically classified as unsuitable (N) [9].
Parameters in Land Evaluation
Temperature
Temperature or temperature is the degree of hot or cold which is measured based on a certain scale using a thermometer. Land characteristics from the Soil Temperature (tc) variable used in assessing land suitability classes are determined from the average temperature characteristics.
Rainfall
Rainfall is the height of rainwater (in millimeters) that is received on the surface before experiencing surface flow and infiltration or seepage into the ground. This needs to be considered to increase corn production [10].
Humidity
Humidity is the amount of water vapor in the air. Humidity can be seen from the climate classification of a place. According to Schmidt and Ferguson, the type of rain in an area is determined based on the Q value, namely by considering the number of dry months and wet months in one year multiplied by 100%.
Soil Drainage
Soil drainage assessment consists of Fast, Somewhat Fast, Good, Somewhat Good, Somewhat Inhibited, Inhibited, Very Inhibited.
Soil Texture
It is the relative ratio of grains of sand, dust, and clay.
Nutrient Availability
What is measured in nutrient availability are C (%), N (%), C/N, P2O5 HCl 25% (mg/100 gr), K2O (Morgan) (ppm), P2O5 Bray (ppm), CEC (col( +)/kg clay), C-organic [11].
Results and Discussion
Result
In determining the research location, the GIS (Geographic Information System) method was used based on climate, soil, topography, and surface water resources [3]; [12], as well as slope and soil type [13], some of these parameters are limiting factors in corn cultivation [14] ; [15].
The results of the analysis of actual and potential land suitability maps in land map units (LMU) 1 – 5 for the area of corn plant development can be seen in the map image below:
Discussion
In principle, land suitability assessment is carried out by matching soil and physical environmental data with a land suitability table for corn plants which has been prepared based on land use requirements including commodity growth/living requirements. [16] In assessing land suitability, it is necessary to determine the actual state (actual land suitability) or the potential state (potential land suitability). The potential state is achieved after carrying out improvement efforts (Improvement = I) toward each limiting factor to achieve the potential state
Climate Suitability Evaluation
Climate greatly influences almost all aspects of agricultural activities, both in long-term and short-term processes, the need for climate information will directly influence planting patterns, types, and even government policy strategies. Climate change will also result in a decrease in crop yields which indirectly causes a decrease in farmers’ income [17]; [18].
Temperature
Temperature is an environmental factor that influences plant growth and development because every plant needs an appropriate temperature to grow and develop well. If plants are planted outside their climatic regions, their productivity is often not as expected [19]. The suitable temperature for corn plants is between 21- 28°C. This air temperature range is important in influencing the stages of plant development. The optimum air temperature for the photosynthesis process ranges from 10- 30°C [20]. If this temperature condition is adjusted to the suitability class for corn plants, it is included in class S1, which is very suitable because the temperature at the research location is 26,50C, which means this figure is between 21-28oC.
Rainfall
Rainfall is one of the climate elements that plays a very big role in supporting the availability of water on land. Rainfall greatly influences the growth and development of corn plants. To assess land suitability, it is usually expressed in terms of the amount of annual rainfall, the number of dry months, and the number of wet months. [21] groups regions based on the number of wet months and dry months respectively [22]. A wet month is a month that has rainfall >200 mm, while a dry month has rainfall of 100 mm) and is a dry month. (The trend of rising and falling temperatures is an indication that the possibility of rainfall in the last 10 years could reach greater amounts. Suitable rainfall (S1) for corn plants is 500-1200 mm on average/year [9], the results of the land evaluation analysis at the 5th SPL are only in the range > 1400 mm so it can be categorized as unsuitable (N).
Humidity
Air humidity affects the water content in the air and the air in the soil. The higher the humidity value, the higher the water content in the air. If the humidity is too high, it will reduce the evapotranspiration process and the absorption capacity of plant roots to obtain nutrients, whereas if it is too low, evapotranspiration will occur very quickly so that it is not balanced by the supply of water by the roots and causes the plants to wilt. The best humidity for corn plants is <75% [9]. The results of climate suitability analysis at the research location include quite suitable humidity (S2), namely 75 – 85 % actual with an average humidity of 83%.
Texture
Texture is a characteristic of a soil type that cannot be changed by agronomic treatment, but can only be done by managing it so that the soil moisture is optimal. If the soil contains a lot of clay, the soil can store large amounts of water, but the water does not easily seep into the soil because water will flow more easily on the surface and cause erosion, while sandy soil is more easily seeped and cannot store water. Soil texture is said to be good if the composition of sand, dust, and clay is almost balanced. This kind of soil is called clay soil. The finer the grains of sand, the stronger the soil holds water and nutrients. The texture suitable for corn plants is fine, somewhat fine, and medium [9]. The results of the actual suitability analysis at the research location are at a fine, rather fine level so it is classified as very suitable (S1) at LMU 5 Villages so that the texture in this area is not a limiting factor.
Drainage
Soil drainage is the speed at which water absorbs from the soil or the condition of the soil which indicates the duration and frequency of water saturation. Poor drainage makes it difficult for water to seep into the soil or it absorbs very easily so the water disappears quickly. The relationship between these parameters and climate parameters influences groundwater flow ([23]; [24].
Drainage suitability is very necessary for plants, [25] including for corn cultivation in Basi Dondo District, the results of the land evaluation are included in suitability class S1, namely very suitable.
Cation Exchange Capacity
Cation exchange capacity (CEC) is defined as the capacity of the soil to absorb and exchange cations in the soil. Soil colloids can absorb and exchange several cations, including Ca, Mg, K, Na, NH4, Al, Fe, and H. Bases that can be exchanged include Potassium (K), Sodium (Na), Calcium (Ca), and Magnesium (Mg) [26] Cation exchange capacity (CEC) is a chemical property of soil that is closely related to soil fertility. Soil with a high CEC can absorb and provide nutrients better than soil with a low CEC because these nutrients are not easily washed away by water [27]. The average CEC at the research location was classified as quite suitable (S2/SPL 2 and 4) ≤16 and very suitable (S1/SPL1.3) namely 22.93. To improve this limiting factor, it is necessary to limit and add organic or organic fertilizer. Soil with a high organic matter content has a higher CEC, likewise, young soil with a new level of weathering starting from soil with an advanced level of weathering has a low CEC value [28].
Soil Acidity (pH H2O)
pH is the level of soil acidity that regulates the absorption and distribution of cations by soil particles. High soil pH of less than 6 causes the elements Forfor, Calcium, Sulfur, Calcium, Magnesium, and Molybdenum to decrease rapidly, while soil pH higher than 8 will cause the elements Nitrogen, Iron, Manganese, Boron, Copper, and Zinc availability is relatively small [29]. The pH for corn plants is 5.5 – 8.2, while at the research location, the pH reaches 4.9 or marginally suitable (S3/ LMU 2) and very suitable (S1/ LMU 2,3,4 and 5) with a pH of 6.01. The way to overcome LMU 2 is by liming and adding organic materials.
C-Organic
C-organic or organic material content is plant remains that act as a reservoir for plant nutrients. The amount of organic C content in the soil can also determine the amount of organic matter content in the soil [30]. Organic matter is generally found on the surface of the soil, the amount is very small, around 3-5% but its influence is quite large on soil properties. Organic matter can function to improve soil structure, as a source of nutrients, the capacity to increase the CEC value of the soil, a source of energy for soil microorganisms, and increase the soil’s ability to retain water. C-organic for corn plants is suitable > 0.4% [9] at the research location in the very suitable category (S1), namely 0.76 – 3.01%. Organic materials increase soil fertility, plant growth, and higher crop yields [31].
Efforts to Improve Limiting Factors
Based on the analysis carried out, the limiting factors include Cation Exchange Capacity, pH, and C-Organic, then the characteristics of available nutrients, namely N-total, P2O5, and K2O, while the erosion hazard characteristics are slope and actual erosion hazard. Improvement of limiting factors for drainage is by improving the irrigation system. Improving the limiting factors for nutrient retention, including cation exchange capacity, pH, and organic C, can be done by liming and adding soil organic matter. Improvements in the limiting factors for available nutrients, including N-total, P2O5, and K2O, can be done with balanced fertilization with the right dose and at the right time. Improving the limiting factors for erosion hazards which include slopes can be done by making terracing, planting parallel to contours, cultivating land according to contours, and planting ground covers.
Conclusions
Based on the research results, the suitability of land for developing corn plants in Basi Dondo District, Tolitoli Regency is as follows:
a. The overall LMU (LMU 1- 5) which is the main limiting factor is high rainfall, and is in the category of Unsuitable Class (N), while other limiting factors are nutrient retention (S2), which can be increased to (S1) and Slope (S2 )
b. These limiting factors can be done by making terracing, planting cover crops, adding organic material, liming, and fertilizing.
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