APSIM-Tropical Pasture: A model for simulating perennial tropical grass growth and its parameterisation for palisade grass (Brachiaria brizantha)

Autor(es)

Bosi, Cristiam ^[1] ; Sentelhas, Paulo Cesar ^[1] ; Huth, Neil Ian ^[2] ; Macedo Pezzopane, Jose Ricardo ^[3] ; Andreucci, Mariana Pares ^[4] ; Santos, Patricia Menezes ^[3]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, ESALQ, Av Padua Dias 11, BR-13418900 Piracicaba, SP - Brazil

^[2] CSIRO, 203 Tor St, Toowoomba, Qld 4350 - Australia

^[3] Embrapa Pecuaria Sudeste, Rodovia Washington Luiz, Km 234, POB 339, BR-13563776 Sao Carlos, SP - Brazil

^[4] Lincoln Res Ctr, AgRes, Private Bag 4749, Christchurch 8140 - New Zealand

• Tipo de documento: Artigo Científico
• Fonte: AGRICULTURAL SYSTEMS; v. 184, SEP 2020.
• Citações Web of Science: 0

Resumo

Tropical grasses are used as forage, to produce energy from biomass, for land restoration and carbon sequestration, among other applications. Many modelling approaches have been employed to simulate tropical grasses growth, but these have several limitations that must be solved by adapting them or creating new models. This study aimed to develop a tropical pasture model in the Agricultural Production Systems Simulator (APSIM) modelling framework, and to parameterise it to simulate Brachiaria brizantha `BRS Piata' growth, under grazing and cut-and-carry management. For this, three field experiments were conducted in the South-east of Brazil where pasture growth was measured in a cut-and-carry system, with irrigated and rainfed treatments, and in a rainfed grazing system. Model evaluation was performed through precision and accuracy indices and simulation errors. Under cut-and-carry management, forage productivity was estimated with R-2 values from 0.89 to 0.94, Willmott agreement indices between 0.97 and 0.98, and Nash-Sutcliffe Efficiency values of 0.88 to up to 0.92. This demonstrates the capacity of the APSIM-Tropical Pasture model to simulate tropical pastures. Simulation of phenology, early growth after sowing, partitioning and senescence during flowering, and reallocation and retranslocation of plant dry matter and nitrogen were important aspects for this capacity. Then, APSIM-Tropical Pasture can be used to simulate tropical pastures, but several requirements for further improvements have been identified, such as to improve the simulations of flowering for palisade grass, N effects on pasture yield, reallocation and retranslocation processes. Under grazing management, forage productivity was estimated with R-2 = 0.80, Willmott agreement index of 0.91, and Nash-Sutcliffe Efficiency value of 0.62. Despite these reasonable results, simulations presented problems, since does not take into account the effect of grazing animals on pastures. This indicates that, in its current form, APSIM-Tropical Pasture is not able to simulate pastures under grazing effectively. However, this simulation of grazed system was important to identify main modelling constraints and direct future research to improve knowledge of processes and interactions needed for pasture model development. (AU)

• Processo FAPESP: 16/01532-4 - Parametrização do modelo APSIM para estimar as interações entre árvore e pastagem e o crescimento do capim Piatã em sistema silvipastoril
• Beneficiário: Cristiam Bosi
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Doutorado
• Processo FAPESP: 14/11931-8 - Parametrização e avaliação de modelos mecanísticos para estimativa da produtividade de Urochloa brizantha cv. Piatã em sistema silvipastoril
• Beneficiário: Cristiam Bosi
• Modalidade de apoio: Bolsas no Brasil - Doutorado