Growth and chlorophyll in noni seedlings irrigated with saline water in substrate with vermicompost

ABSTRACT Irrigation is a limiting factor for the development of crops, and all water sources contain salts, which can accumulate in the soil and in the plant, compromising its development. The use of vermicompost is one of the alternatives to mitigate the negative effects of salts on plants. This organic compost is a soil conditioner and a nutrient source for plants. Thus, this study aimed to evaluate the growth and chorophyll of noni (Morinda citrifolia L.) in response to the salinity of irrigation water in substrates with and without vermicompost. A completely randomized design in a 4 × 3 factorial scheme was used, corresponding to four levels of electrical conductivity of the irrigation water (0.5, 1.5, 3.0 and 4.5 dS m-1), in three soil substrates (without humus, with 33.33 and 66.66% of humus). Three months after germination, the following variables were evaluated: plant height; stem diameter; number of leaves; chlorophyll index (a, b and total) in the leaves; and fresh and dry matter of shoots and roots. The increase of salinity in irrigation water negatively influences growth in height, stem diameter, biomass production and chlorophyll a and total indexes, but with lower intensity in substrates with humus, that improves the fertility of the substrate and favors the growth of noni plants, regardless of the salinity of the irrigation water; however, its beneficial effect decreases with the intensification of electrical conductivity of irrigation water.

摘要
灌溉是作物生长发育的限制性因素，且所有水源均含有盐分，盐分可在土壤与植株体内累积，进而损害作物生长发育。施用蚯蚓粪（vermicompost）是缓解盐分对植株负面影响的可行途径之一，该有机堆肥兼具土壤改良剂与植物营养源的双重功能。据此，本研究旨在探究施用与未施用蚯蚓粪的基质中，诺丽（Morinda citrifolia L.）的生长及叶绿素水平对灌溉水盐度的响应规律。
本研究采用4×3因子完全随机试验设计，设置4个灌溉水电导率梯度（0.5、1.5、3.0及4.5 dS·m⁻¹），并搭配3种土壤基质处理：不含腐殖质、添加33.33%腐殖质及添加66.66%腐殖质。播种发芽3个月后，对以下指标进行测定：株高、茎粗、叶片数、叶片叶绿素a、叶绿素b及总叶绿素指数，以及地上部与根部的鲜重和干重。
研究结果表明：灌溉水盐度升高会显著抑制诺丽的株高生长、茎粗发育、生物量累积以及叶绿素a与总叶绿素指数，但该抑制效应在添加腐殖质的基质中显著减弱；腐殖质可提升基质肥力，无论灌溉水盐度如何，均能促进诺丽植株生长，但其有益效应会随灌溉水电导率的升高而逐步减弱。