Yield performance of four soybean varieties in rainfed lowland areas

Introduction

The average of national soybean demand is around 2,400,000 t per year. Meanwhile, domestic production is only to reach 800,000 t (33.33%) of the national need (Directorate General of Food Crops, 2017). To fulfill these food needs, additional imports are needed. According to Harefa (2013) that Indonesia's dependence on imports is due to domestic soybean production does not suffice national needs, while soybean demand increases every year. Therefore, soybean development in several central provinces needs to be improved. 

Soybean planted area and harvested area in South Sulawesi from 2006 to 2010 fluctuated with an average of 22,307 ha and 17,009 ha, respectively (Dinas Pertanian Tanaman Pangan dan Hortikutlura Provinsi Sulawesi Selatan, 2013). Meanwhile, soybean production and productivity in the period of 2014 to 2018 in South Sulawesi were 47,179 t and 1,512 t/ha, respectively (Kementerian Pertanian, 2018). To increase the production and productivity of soybeans, it is necessary to support new high-quality seed varieties. One of the new high yielding varieties is Biosoy.

Adaptive superior varieties and the use of quality seeds are important components to meet the demand for soybeans (Sumarno and Adie, 2010; Adisarwanto et al., 2013). The use of certified superior varieties seeds is believed to be able to make a real contribution to increasing crop productivity (Nugrahaeni et al., 2008, Directorate General of Food Crops, 2015). In 2008, the use of certified soybean seeds at the farm level was only 2% (Suastika and Kariada, 2012). Hanafi et al. (2014) reported that one of the causes of the decline in soybean production was due to the unbalanced availability and need for superior soybean seeds in the field. The need for quality seeds in each growing season often cannot be fulfilled due to limited availability in the field, so farmers use consumption soybeans as seeds. Furthermore, Mejaya (2011) reported that until now the use of superior soybean varieties has only reached 20% and the use of certified seeds is only 10%.

This is driven by the shelf life of soybeans which are not durable, so it is necessary to have a good seed system so that seeds are available when needed at affordable prices. 

The soybean varieties recently released by Balai Besar Penelitian dan Pengembangan Bioteknologi dan Sumberdaya Pertanian are Biosoy 1 with a potential yield of 3.3 t/ha and Biosoy 2 3.5 t/ha. Both varieties have wide yield stability in various test locations. The Biosoy 1 and Biosoy 2 lines had relatively the same age (83-84 days), or 7-8 days deeper than the Grobogan variety and 3-4 days earlier than Anjasmoro. The number of pods of these two varieties was more than that of the Grobogan variety but less than the number of pods of Anjasmoro. Seed size can be seen from the weight of 100 seeds of Biosoy 1 and Biosoy 2, respectively 21.74 and 22.35 g/100 seeds, much larger than Anjasmoro's 16.14 g/100 seeds and also larger than Grobogan's 20.72 g/ 100 seeds. The Biosoy 1 and Biosoy 2 varieties have large and sturdy stems characterized by wide stem diameters. Morphologically, Biosoy 1 has a different flower color and hypocotyl color. Biosoy 1 flower color and hypocotyl color is green, while Biosoy 2 flower color and hypocotyl color is purple (Balai Besar Penelitian dan Pengembangan Bioteknologi dan Sumberdaya Pertanian, 2019). This indicates the importance of new high yielding varieties to be introduced and adapted in soybean production centers. The purpose of this study was to determine the growth and yield performance of four soybean varieties in rainfed rice fields in Maros Regency.