Effects of Closing Cut Date and Nitrogen Fertilization on Seed Yield and Seed Quality in Two Novel Cultivars of Urochloa spp.

Abstract

Two field trials were conducted in Thailand to determine an appropriate closing cut date (CCD) and rate of nitrogen application (N-rate) to maximize seed yield and seed quality of the two novel cultivars (cv.) of Urochloa spp. (Synonym Brachiaria spp.), cv. ‘OKI-1’ (an open-pollinated tetraploid Urochloa ruziziensis (R. Germ. and C.M. Evrard) Crins originated from cv. ‘Miyaokikoku-ichigou’) and cv. ‘Br-203’ (U. ruziziensis cv. ‘Miyaokikoku-ichigou’ × U. hybrid cv. ‘Mulato’). The following treatments were evaluated in this study: four CCDs (uncut, 15 June, 1 July, and 15 July) and four N-rates (0, 50, 100, and 150 kg/ha). The cv. ‘OKI-1’ showed somewhat differences in tiller number/m2 (TN), fertile tiller percentage (FTP), inflorescence number/tiller (IN/T) and spikelet number/raceme (SN/R) with the CCD, while the cv. ‘Br-203’ showed only in SN/R. However, TN and SN/R were highest for 15 June, and FTP and IN/T were highest for 1 July in cv. ‘OKI-1’. The cv. ‘OKI-1’ showed the highest total seed yield (TSY), pure seed yield (PSY), and pure germinated seed yield (PGSY) for 1 July, followed by 15 June, and the cv. ‘Br-203’ showed the highest TSY, PSY, and PGSY for 15 July, followed by 1 July. Nitrogen (N) fertilization showed a negative effect on TSY for both the cultivars due to the higher N content in the soil. Withholding N fertilizer, a CCD in late-June to early-July and early-July to mid-July is recommended for cv. ‘OKI-1’ and cv. ‘Br-203’, respectively.