岸杂一号狗牙根草的缺镁症状及镁肥效应

MAGNESIUM DEFICIENCY SYMPTOM AND MAGNESIUM FERTILIZER EFFECT ON BERMUDAGRASS

在粤西地区玄武岩、花岗岩和浅海沉积物三种主要母质发育的砖红壤上,进行牧草(岸杂一号狗牙根草)镁肥盆栽试验。由花岗岩和浅海沉积物发育的砖红壤,不施镁时,各次收割的牧草干物质含镁量大都低于20%,并先后出现缺镁症状。其缺镁症状表现为斑状失绿,首先在两边叶缘出现近乎成对而对称的小黄斑,这些小黄斑进而向中央扩展连接,使叶子上半部分的绿色部分不连续,似念珠状。该牧草的缺镁临界指标为地上部干物质含镁(Mg)0.15%。牧草的镁肥效应因土而异,花岗岩发育的砖红壤,施镁处理牧草平均增产64.4%,镁肥效应最佳;浅海沉积物发育的砖红壤,施镁处理平均增产17.2%,肥效次之;玄武岩发育的砖红壤,镁肥效应不明显。在施用量不大的情况下,镁肥对牧草氮、磷、钾含量影响不大,对缺镁土壤来说,施镁使牧草生长良好,氮、磷、钾的总吸收量增加。

Twelve soils derived respectively from basalt, granite and marine deposit in the western parts of Guangdong Province were collected and for planting grass (Coastcross-1 Bermuda grass) in the greenhouse. Magnesium deficiency symptoms with chlorotic spots appeared in grass growing in the soils derived from granite and marine deposit, and plants responded well to magnesium fertilizer. Grass growing in soils derived from basalt showed no symptoms of magnesium deficiency, and did not respond to magnesium fertilizer. Incipient symptoms of magnesium deficiency appeared when the grass contained 0.15% Mg or less. Magnesium fertilizer had no strong influence on N, P and K concentration in the grass. But in magnesium deficient soils it made the grass grow well and increased the total N, P and K uptake of the grass significantly.