EFFECTS OF SOIL WATER AVAILABILITY AND ORGANIC MATTER CONTENT ON FRUIT YIELD AND SEED OIL CONTENT OF CASTOR BEAN1

ABSTRACT The objective of this study was to assess the sensitivity of the castor bean cultivar “BRS 188 Paraguaçu” to available soil water for plants and soil organic matter content based on their effects on fruit yield and seed oil content. A 2 × 4 factorial experiment was conducted from October 2008 to March 2009 under field conditions using randomized complete block design; two soil organic matter contents (5.0 and 25.0 g·kg−1) and four available soil water levels for plants at the irrigation time (70, 80, 90, and 100% of the total available soil water) with three replicates were tested. On each experimental unit measuring 100 m2, 50 plants were cultivated with a spacing of 2 m × 1 m (24 useful and 26 border plants). Analysis of variance (F test) was performed; qualitative factors (soil organic matter) were compared by Tukey's test and quantitative factors (available soil water) by regression analysis. Increased soil organic matter and available soil water for plants substantially increased productivity; however, seed oil content, mean 100-seed mass, mean 100-fruit mass, and seed:fruit ratio were affected by available soil water content alone. Therefore, the tested cultivar is sensitive to reduced available soil water content, which severely decreases its productivity.

摘要 本研究旨在基于土壤有机质（soil organic matter）含量与植物有效土壤含水量（available soil water）对蓖麻品种“BRS 188 Paraguaçu”的果实产量及种子含油率的影响，评估该品种对这两种土壤因子的敏感性。本研究于2008年10月至2009年3月在田间条件下开展，采用随机完全区组设计（randomized complete block design）设置2×4析因试验（factorial experiment），共设置2个土壤有机质含量梯度（5.0与25.0 g·kg⁻¹）、4个灌溉时期植物有效土壤含水量梯度（占总有效土壤含水量的70%、80%、90%与100%），并设置3次重复。每个试验单元面积为100 m²，种植50株蓖麻，种植规格为2 m×1 m（其中24株为实测株，26株为边际株）。采用方差分析（analysis of variance，F检验）对数据进行统计分析；其中定性因子（土壤有机质）采用Tukey检验（Tukey's test）进行多重比较，定量因子（有效土壤含水量）则采用回归分析进行解析。提升土壤有机质含量与植物有效土壤含水量均可显著提高蓖麻产量；但仅有效土壤含水量会对种子含油率、百粒重、百果重及种果比产生影响。因此，供试蓖麻品种对有效土壤含水量降低具有敏感性，该胁迫会显著降低其产量。