عنوان مقاله [English]
Application of organic fertilizers in sustainable agriculture systems improves yield sustainability of field crop. Safflower (Carthamus tinctorius L.) is native to Middle East and belongs to the Asteraceae family. It is resistant to saline conditions, water stress, and can reach the deep-lying water of soil. The humic acid (HA) mentioned as an environmentally friendly, organic matter with low levels of hormonal-like compounds is useful in improving agriculture production (Samavat and Malakuti 2006). The HA influence on plant growth depends on the source, concentration and molecular weight of the substance. Vermicompost is produced by earthworms, mainly Eisenia foetida, it has higher levels of available nutrients compared to the original materials of composts produced by other methods. Recent evidences suggest that using different amounts of vermicompost increased vegetative traits and concentration of minerals in sunflower. However, there has been little discussion about organic farming of safflower. The main objectives of the present study were to determine the effect of organic treatments on yield, yield components, and growth indices of safflower and to compare it with conventional agriculture.
Materials and methods
This research was conducted in Agricultural and Natural Resources Research Station in Kerman, Iran during 2012–2013. It was carried out in a randomized complete block (RCB) design and had three replications. The current research has been performed to investigate the effects of two different sources of organic fertilizer on spring safflower. Four levels of vermicompost (V: 0, 3, 6 and 9 t ha-1) were considered in the main plots. Liquid humic acid at four different concentrations (HA: 0, 1000, 2000 and 3000 ppm) were examined and kept in the subplots. Humic acid as a foliar treatment on leaf surface was applied twice at the beginning of stem elongation and at flowering times. In this study, aimed to compare organic farming with conventional farming, inorganic fertilization was considered as a conventional agriculture (CA) for each replication. Growth indices were assessed based on the growing degree days (GDD). After harvested, the head number per plant, seed number per head, 1000 seed weight and seed yield were evaluated. Also, two separate statistical analyses were used for comparison organic treatments with each other and conventional agriculture with organic treatments.
Results and discussion
The results showed that the maximum LAI, TDW and CGR have been determined at 9 t ha-1 vermicompost and 3000 ppm humic acid in CA. Likewise, the results indicated that vermicompost leads to a significant increase in seed yield, flower yield and yield components except 1000 seed weight. Head number per plant, seed number per head and seed yield were affected by humic acid treatments and increased significantly from 1000 to 3000 ppm. However, 1000 seed weight decreased with the increasing concentration of humic acid. It should be mentioned that, 9 t ha-1 vermicompost and 3000 ppm humic acid produced the highest head number per plant (24.75), seed number per head (56.71) and seed yield (4268.17 kg ha-1) in two years that in comparison with CA were increased 79.22%, 30.37% and 89.49%, respectively.
The results of this study indicated that acceptable yield was obtained with increasing HA concentration at lower levels of vermicompost compared to the higher amount of vermicompost without HA that is economically beneficial. For example, application of 6 t ha-1 vermicompost + 3000 ppm HA had higher seed yield (3027.08 kg ha-1) than 9 t ha-1 vermicompost without foliar application of HA (2722.5 kg ha-1), although there was no significant difference between them.