燕麦/小麦间作对小麦生长和锰营养的影响

The effects of intercropping oat and wheat on growth and manganese nutrition of wheat

通过根系分隔的盆栽试验,研究了燕麦小麦间作对小麦生长及其锰营养的影响。结果表明:根系不分隔处理,小麦地上部干重和植株吸锰量都高于其他两种分隔方式;而根系完全分隔处理,小麦地上部植株锰含量高于其他两种分隔方式;根系不同分隔方式对川麦28土壤DTPAMn含量几乎没有影响,小麦9023土壤DTPAMn含量则以完全分隔处理高于另外两种分隔方式。推测在该间作体系中,燕麦可能通过根系分泌物来活化土壤难溶性的锰氧化物,从而促进了小麦的生长,改善了小麦的锰营养,但因其竞争能力不如小麦而消弱了自身的生长。具体原因有待于进一步试验验证。试验还发现,种植燕麦后土壤的DTPAMn含量要高于种植小麦后的土壤,而且燕麦地上部植株锰含量也比小麦高,表明燕麦活化、吸收土壤锰的能力强于小麦。不同间作组合时,小麦各项研究指标无一致的规律性,说明在促进小麦生长、改善小麦锰营养的能力方面,本试验采用的3个燕麦品种之间无明显差异。

Manganese （Mn） deficiency in wheat is a typical nutritional problem on calcareous soils, especially under rice-wheat rotation system. However, wheat yield loss induced by Mn deficiency may be reduced through interactions between two crops with different Mn utilization potentials. In 2003, a pot experiment was conducted at a greenhouse of China Agricultural University to evaluate the effects of oat/wheat intercropping on growth and Mn nutrition of wheat grown in a Mn-deficient soil. The pot experiment included two factors： root-isolation （including solid barrier, mesh barrier and no barrier） and intercropping combination. Two wheat cultivars （Chuanmai28 and 9023） and three oat cuhivars （Bayou 1, Bayou 3 and Jizhangyou 4） were used in this experiment. Each of the 18 treatments （3×2 ×3） was replicated three times. All treatments received the same rates of Ca（NO3）2 （0.3 g N kg^-1）, Ca（ H2PO4 ）2 （0.2 g P2O5 kg^-1） and K2SO4 （0.3 g K2O kg^-1） as NPK fertilizers before planting. The ratios of N：P2 O5：K2O were 1.5：1：1.5. All plants were harvested after 2 months of growth. Shoot dry weight and Mn concentration were measured and shoot Mn uptake was calculated by multiplying biomass by Mn concentration. The original soil was an alluvial paddy soil with pH 7.69, O.M. 34.9 g·kg^-1, exchangeable Mn 1.0 mg·kg^-1, and active Mn 19.0 mg·kg^- 1. Wheat Mn-deficient symptoms were initially observed at the fourth-extended leaf stage of wheat, and the most serious symptoms of Mn deficiency appeared at the sixth-extended leaf stage. But the symptoms gradually diminished as air temperature increased, providing evidence that low temperature is a primary cause for wheat Mn-deficiency. The symptoms of Chuanmai 28 were more sensitive to serious than those of 9023 and no Mn-deficient symptoms of oat were observed, suggesting that Chuanmai 28 was more Mn deficiency than 9023 and both of these two wheat cultivars were more sensitive to Mn deficiency than three oat cuhivars. Compared with the solid barrier and mesh barrier treatments, complete root interaction （no barrier treatment） led to significantly higher shoot dry weight and Mn uptake of the two wheat cultivars. The shoot Mn concentrations of the two wheat cuhivars, however, were higher in the solid barrier treatment than in the other two treatments （ mesh barrier and no barrier）. The DTPA-Mn in soil grown oat was higher than grown wheat across barrier treatments and Mn concentration and Mn uptake of oat genotypes were much higher than those of wheat genotypes. Consequently, we speculate that oat may facilitate the growth and improve the manganese nutrition of wheat under intercropping by activating the insoluble soil Mn oxides with root secretion. Observed increased growth and higher Mn uptake of wheat intercropped with oat （no barrier） provide initial support for this hypothesis