Towards the improvement of furrow irrigation for sugar cane crops in Colombia: a comparative study

Abstract

Sugar cane in the valley of Cauca river, Colombia, is grown in approximately 250.000 ha. The predominant irrigation system is by furrows, used in over 80% of the area. Due to climatic change, rain distribution has become unpredictable. In addition, the increase of the area planted has caused a decrease in the availability of water per hectare. An experiment was developed aimed at finding alternative surface irrigations which could reduce water consumption during the growing cycle, without lowering productivity. It was carried out on a soil of fine francose texture, with a furrow slope of 0,6%, during three successive cuts (plant cane and two ratoons). In this experiment, different modalities of irrigation were compared, using two flows per furrow: traditional flow (3L /s per furrow) and low flow (0,5 L/s per furrow), in comparison to a control treatment without irrigation. Different irrigation modalities in every furrow were established taking into account the distribution of the harvest residue on the field. The following irrigation modalities were tested: every furrow (EF), four furrows irrigated by one without irrigation (4x1), two furrows irrigated by one without irrigation (2x1), one furrow irrigated by one without irrigation (Alternate Furrow: AF), two furrows irrigated in alternating way by tree without irrigation (2x3 alternating-alternating), and one furrow irrigated in alternating way by two without irrigation (1x2 alternating-alternating).No differences were found in the use of water, or crop yield due to the flows used, for the same modality. However, the results showed differences in the amounts of water used, according to the modality of irrigation. Water saving was: 56% in 1x2 alternating -alternating, 52% in 2x3 alternating-alternating, 45% in AF, 19% in 2x1, and 5% in 4x1, compared to the modality of EF. Low flow irrigation in flat areas and fine-texture soils also showed to be viable. RESUMO:A cana de açúcar no vale do rio Cauca (Colombia), é cultivada em cerca de 250000 ha. O sistema de irrigação predominante é a irrigação por sulcos é utilizado por mais de 80% da área semeada. Atribuível à mudança climática, a distribuição de chuvas tem se tornado cada vez mais incerto que, juntamente com o aumento da área cultivada, tem causado uma diminuição na disponibilidade de água para irrigação.Com o objetivo de estudar alternativas de irrigação de superfície, o que levaria a reduzir o consumo da água de irrigação para um ciclo da cultura, sem reduzir a produtividade da cultura, foi desenvolvida uma pesquisa na qual foram comparadas diferentes modalidades de irrigação, e dois caudais por sulco: o caudal tradicional (3 L/ s-sulco) e o caudal reduzido (0, 5 L/ s-sulco) em comparação com um controle sem irrigação.As modalidades de irrigação utilizados foram estabelecidos considerando o arranjo dos resíduos das culturas no campo; os tratamentos avaliados foram: irrigação em todos os sulcos (SC), quatro sulco com irrigação por um sem irrigação (4x1), dois sulcos com irrigação por um sem irrigação...