Root distribution of cactus pear genotypes under different soil water replacement levels

ABSTRACT Knowledge of the cactus pear root distribution system can improve management of the plant by defining the areas of soil best suited to fertilizer application and the installation of soil moisture sensors under irrigation. Thus, the aim of the present study was to assess the root distribution of cactus pear genotypes under different water replacement levels. To that end, a field experiment was conducted in a randomized block design, using genetic material from two cactus pear genotypes (Opuntia fícus-indica Mill. and Nopalea cochenillifera Salm-Dyck) and six water replacement levels based on reference evapotranspiration - ET0 (T1, no irrigation; T2, 15%; T3, 30%; T4, 45%; T5, 60% and T6, 75% of ET0), arranged in split-plot, with irrigation treatments allocated to the plots and the genetic material to the sub-plots, and three replicates. The roots of the cultivars were collected for analysis of root length density (RLD) 390 days after planting. The RDL of very fine roots declines as depth and distance from the plant base increases and total, fine, small and medium RDL rise at higher water replacement levels; 75% of ET0 near the plant base increases RDL; all the root diameter classes are concentrated at a distance of 0-0.20 m from the plant base and depth of 0.10 to 0.25 m; the RDL percentage is higher for the Gigante genotype and Miuda exhibits better root distribution.

Adapting Root Distribution and Improving Water Use Efficiency via Drip Irrigation in a Jujube (Zizyphus jujube Mill.) Orchard after Long-Term Flood Irrigation

Jujube tree yields in dryland saline soils are restricted by water shortages and soil salinity. Converting traditional flood irrigation to drip irrigation would solve water deficit and salt stress. The root distribution reacts primarily to the availability of water and nutrients. However, there is little information about the response of jujube roots to the change from flood irrigation to drip irrigation. In this context, a two–year experiment was carried out to reveal the effects of the change from long–term flood irrigation to drip irrigation on soil water, root distribution, fruit yield, and water use efficiency (WUE) of jujube trees. In this study, drip irrigation amounts were designed with three levels, i.e., 880 mm (W1), 660 mm (W2), 440 mm (W3), and the flood irrigation of 1100 mm was designed as the control (CK). The results showed that replacing flood irrigation with drip irrigation significantly altered soil water distribution and increased soil moisture in the topsoil (0–40 cm). In the drip irrigation treatments with high levels, soil water storage in the 0–60 cm soil layer at the flowering and fruit setting, and fruit swelling stages of jujube trees increased significantly compared with the flood irrigation. After two consecutive years of drip irrigation, the treatments with higher irrigation levels increased root length density (RLD) in 0–60 cm soil depth but decreased that in the 60–100 cm depth. In the horizontal direction, higher irrigation levels increased RLD in the distance of 0–50 cm, while reducing RLD in the distance of 50–100 cm. However, the opposite conclusion was obtained in W3 treatment. Additionally, in the second year of drip irrigation, W2 treatment (660 mm) significantly improved yield and WUE, with an increasing of 7.6% for yield and 60.3% for WUE compared to the flood irrigation. In summary, converting flood irrigation to drip irrigation is useful in regulating root distribution and improving WUE, which would be a promising method in jujube cultivation in arid regions.

Coarse root distribution of Vatica pauciflora (Korth.) Blume in different soil slopes as revealed by root detector

Tree roots have an essential role in absorbing water and nutrients from the soil and supporting tree stability. As an anchor for the tree, the environment can significantly affect root structure but it is rarely investigated due to below ground distribution. The study was aimed to determine the distribution of coarse roots of Vatica trees (Vatica pauciflora) which grows in different soil slopes. Six mature Vatica trees at Bogor Botanical Garden were selected in this study. Root detector as the main tool based on acoustic method was used to evaluate the root distribution. Analysis photogrammetry was carried out to complement the root detector results. The results found that the root detector only can evaluate the radial distribution of coarse root, while root distribution on downward soil cannot be detected. The condition of the site with different slope categories (e.g., flat to steep) affected root distribution patterns. A study on root distribution was useful to assist the evaluation of tree stability and to support arboriculture study.

Study of rice root distribution patterns for breeding of drought tolerant varieties

Root growth and development is one of the morphological characters which related to drought tolerant traits. This study aims to evaluate the root distribution pattern of 30 rice genotypes to support the breeding of drought tolerant varieties. The research was conducted in ICRR greenhouse in Sukamandi, Subang, Indonesia from October to December 2015. Thirty rice genotypes, consisting of cultivars, promising lines (prior to be released as new varieties), and check varieties, were arranged using randomized complete block design with three replications. Seed were planted in mini pots containing a mixture of sand and soil media with a concave sieve at the top. The filter is divided into three zones, namely upper (1), middle (2), and lower (3). The pot was placed in a plastic box filled with water to maintain the humidity. The results showed that Mekongga had the number of tillers, the number of fresh leaves, the number of roots in zone 1, and the total number of roots significantly higher than the best check variety, Salumpikit. In this study, it was found that the amount of metaxylem between genotypes was different. Salumpikit has the most metaxylem among other genotypes. Further research is expected to be carried out both in drought and optimum condition as a control to see the correlation between root architecture with drought tolerance in the field.