Pemodelan pertumbuhan tanaman kedelai (Glycine max (L.) Merril) di bawah cekaman naungan.

Abstract

The objective of this research was to construct a model of soybean’s growth under shade stress. The steps in the modeling consisted of defining the problem, identification of system components, the formulation of models, simulations, validation, and verification of the model. The modeled problem was the system of soybean’s growth under shade stress. The modeled system included four sub-systems, namely: growth, development, shade stress, and water balance. Formulation of the model comprised of making the flow chart, the determination of relationships between variables, making the Model Construction Layer-Stella (MCL-S), and the Equation Layer-Stella (EL-S). Formulation of the model was conducted on each sub-system as a sub model. Sub model of plant growth was structured as a mass flow of energy in the process of photosynthesis, carbohydrate partitioning, and the process of respiration. Sub model of plant devolopment was structured as heat flow based on the concept of thermal units. Submodel of shade stress was based on the response variables to shade stress, i.e. the ratio of chlorophyll a/b, and light compensation point. Submodel of water balance was structured as a mass flow of water from the process of infiltration, evaporation and transpiration. Model Construction Layer -Stella was used for simulation by entering the model inputs. The required input were the value of shade level, the ratio of chlorophyll a/b, and light compensation point, field capacity, permanent wilting point, and agroclimate data elements. The simulation results of the organs and total dry weight of soybean cultivars Ceneng and Godek, showed logic (valid) results and in line with the results of the actual system (verified). The model can be used to predict growth of soybean plants under shade stress (soyLi model).

Pertumbuhan tanaman sebagai suatu proses yang sangat kompleks menja-dikan pertumbuhan tanaman sebagai objek yang cukup rumit untuk dipelajari apa adanya, sehingga diperlukan pendekatan pertumbuhan tanaman sebagai suatu sistem. Model merupakan penyederhanaan dari sistem, sehingga pemodelan merupakan pendekatan komprehensif untuk mempelajari pertumbuhan. Tujuan penelitian ini adalah untuk menyusun model pertumbuhan tanaman kedelai di bawah cekaman naungan melalui kegiatan pemodelan. Penelitian dilaksanakan dengan menggunakan penelusuran studi pustaka dan percobaan. Penelusuran studi pustaka dimulai bulan April 2010 sampai dengan Juni 2011. Percobaan dilakukan pada bulan Maret sampai dengan Juni 2011 di Kebun Percobaan Leuwikopo, Departemen Agronomi dan Hortikultura, Fakultas Pertanian, Institut Pertanian Bogor. Kegiatan pemodelan terdiri atas pendefinisian masalah, identifikasi kom-ponen sistem, penyusunan model, simulasi dan validasi, serta verifikasi model. Penyusunan model meliputi pembuatan diagram alir (flow chart), penentuan hubungan antar peubah, pembuatan model construction layer-Stella (MCL-S), dan penyusunan equation layer-Stella (EL-S).