陕北黄土丘陵沟壑区水土保持耕作及施肥下农田土壤种子库特征

为了探明多年免耕下农田恶性杂草发生的机理,提高保护性耕作下作物对农田恶性杂草持久稳定的抑制效果,依据陕西安塞田间4a的定位试验, 采用小区调查取样和室内实验相结合的方法,从物种组成、密度特征、多样性以及相似性特征等方面,研究了黄土丘陵旱作农区大豆(Glycine max)、玉米(Zea mays)、红小豆(Semen Phaseoli)、马铃薯(Solanum tuberosum)在翻耕化肥(CF)、翻耕有机肥(CM)、翻耕无肥(CN)、免耕化肥(NF)、免耕有机肥(NM)、免耕无肥(NN)等水平下的农田土壤种子库.结果表明: (1) 4种作物24种土样中共萌发出12个物种1965株幼苗,隶属于7科12属.1年生杂草占94%,棒头草(fugax nees ex steud)、苋菜(Acalypha australis)、马唐(Digitaria sanguinalis)、早熟禾(Poa sphondylodes)为优势种,占87%.(2)在0～20cm土层不同处理间,土壤种子库的密度变动于(282.9±63.4)～(7482.5±1078.3)粒·m- 2,其中,红小豆小区＞马铃薯小区＞大豆小区＞玉米小区;翻耕小区＞免耕小区;有机肥小区＞化肥小区＞无肥小区,差异极显著. (3)土壤种子库密度NM红小豆最高,NN玉米最低;丰富度指数CF大豆为2.30;NN红小豆为0.29;多样性指数NN大豆为5.56,CF红小豆为0.45;生态优势度NF玉米为1.35,CF大豆为0.17.玉米、大豆是黄土丘陵沟壑旱作农区免耕下农田抑制杂草最为适宜的作物, NM玉米、NF大豆和NM大豆是黄土丘陵沟壑旱作农区较优的耕作管理方式,其农田的生态效应是能够竞争性抑制恶性杂草的蔓延,优化土壤环境,杂草的多样性高且比较均衡,杂草的土壤种子库密度低.

The soil seed bank characteristics in cropland under different conservation tillage and fertilization regimes in Loess Hill and Gully Region

To better understand the mechanism of weed occurrence and suppression effect of crops on weeds, we conducted a 4-year field experiment in 4 crops under different tillage and fertilization regimes in Ansai, Shaanxi, China. The species composition, seed density, diversity and the similarity were measured in soil seed bank of soybean (Glycine max), corn (Zea mays), Red Bean (Semen Phaseoli ) and potato (Solanum tuberosum). The tillage and fertilization treatments in each crop included till-chemical fertilizer (CF), till-organic manure (CM), till no fertilizer (CN), no-till chemical fertilizer (NF), no-till-organic manure (NM), and no-till-no fertilizer (NN). The results showed that: (1) There were 12 weed species in 1965 seedlings from 24 soil samples in 4 crops. These species belonged to 7 families and 12 genuses and 94% of them were annual weeds. Bangtou grass (fugax nees ex steud), amaranth (Acalypha australis), large crabgrass (Digitaria sanguinalis) and Poa(Poa sphondylodes)were the dominant species and accounted for 87%;(2) In 0-20cm soil of different treatments, weed density ranged from (282.9 ± 63) to (7482.5 ±1078.3) seeds · m-2. There were significant differences (P<0.01) in weed density among crops, tillage systems, and fertilization regimes. The ranking of weed seed density was Red Bean plot> potato plot > soybean plot > corn plot among 4 crops, tillage plot > no-tillage plot between 2 tillage treatments, and organic fertilizer plot > Fertilizer plot > no fertilizer plot among fertilization treatments;(3) Soil seed bank had the highest weed density in NM Red Bean and the lowest density in NN corn. The rich index was the highest (2.30) in CF soybean and the lowest (0.29) in NN Red Bean. The diversity index was the highest in NN soybean (5.56) and the lowest in CF Red bean (0.45). The ecological advantage of NF corn was the highest (1.35) and that of CF soybean was the lowest (0.17). Among the fertilization treatments, the similar coefficient of soil seed bank ranged from 0 to 0.63 in tilled system and from 0.67 to 0.92 in no-till system. As a result, corn and soybean were optimal crops to inhibit weeds in the dry land farming region of the Loess Plateau, and the best treatments were NM corn, NF soybeans and NM soybean. The ecological benefits of these crops include inhibiting the spread of weeds competitive to crop, maintaining high diversity and equilibrium of weeds, decreasing weed density in soil seed bank and optimizing soil environment.