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 本研究旨在以果实产量与种子含油率为响应指标，评估蓖麻品种"BRS 188 帕拉瓜苏"对植株可利用土壤水（available soil water）与土壤有机质（soil organic matter）含量的敏感性。本试验于2008年10月至2009年3月在田间开展，采用完全随机区组设计，设置2×4因子试验方案：设置2个土壤有机质含量水平（5.0与25.0 g·kg⁻¹）、4个灌溉时植株可利用土壤水水平（占总可利用土壤水的70%、80%、90%、100%），每个处理设置3次重复。每个试验小区面积为100 m²，种植50株蓖麻，株行距为2 m × 1 m，其中24株为有效植株，26株为边界植株。采用方差分析（analysis of variance, F检验）对试验数据进行统计分析；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（可利用土壤水）则采用回归分析（regression analysis）。提升土壤有机质含量与植株可利用土壤水水平可显著提高产量；但种子含油率、百粒重、百果重以及种果比仅受可利用土壤水含量的影响。综上，供试蓖麻品种对可利用土壤水含量降低较为敏感，土壤有效水不足会显著降低其产量。