# Maize Replacement for Controlling Invasive _Eupatorium adenophorum_
## 3 Results and Discussion
### Implications for Agriculture  
_E. adenophorum_ could readily propagate by sexual or asexual reproduction [42]. _E. adenophorum_ could produce about 260 to 280 thousand seeds per square meter, and residue rhizomes or stems could also sprout new buds. It had a strong advantage in resource competition for up to 15 years [43]. Subsequently, _E. adenophorum_ decreased dramatically in seed yield and entered a senescence phase, reducing the competition for resources between _E. adenophorum_ and other plants. During this period of natural community succession, _E. adenophorum_ successfully competed with other plants for water and fertilizer, which reduced soil fertility and caused land degradation [44; 45; 46]. Invasion of _E. adenophorum_ could destroy the local plant ecosystem within several years. The technology of replacement control eliminated _E. adenophorum_ habitat by reducing the seed bank and removing the current community of plants. Many _E. adenophorum_ seeds in the surface soil layer are plowed into deeper soil layers (Figure 2a) because the germination rate is inversely proportional to seed depth [26] and plowing reduced seedling emergence. Ungerminated seeds would be buried deeper in soil and died after many cycles of plowing and replacement planting. The surface seed bank that had potential to become a new population was effectively reduced. Both the plant height and total leaf area in the maize treatments were larger than _E. adenophorum_ in the CK and CS treatments (Tables 3 and 4). Tall and leafy maize plants effectively intercepted illumination that would have reached the seeds of _E. adenophorum_. The light penetration rates in the M2, M3 and M4 treatments at 10 cm off the ground ranged from 2.32 to 3.63% (Figure 3b). In comparison, the penetration rates in the M1 treatment at different heights above ground were 100%. According to the control effect (100%) of maize replacement, the seed germination rate of _E. adenophorum_ was greatly inhibited by maize (Tables 3 and 4). This result was attributed to the large amount of light required for seed germination [47]. Furthermore, replacement planting (in the M2, M3 and M4 treatments) with commercial crops limited weed community recovery, enhanced the control effect and released space to facilitate ecosystem recovery [12]. The control mechanism is shown below: both _E. adenophorum_ and maize germinated with the advent of the rainy season. Maize seedlings broke through the top soil one week after seeds were sowed and entered the jointing stage within 30 d. During the vigorous growth period (about 63 d), maize captured most of the available light resources due to its high stalk and canopy density. This monopoly of light capture was an advantage sustained to harvest (about 130 d). During its growth period, maize sprouted and grew faster than _E. adenophorum_. Maize gradually formed a shielding, which resulted in the canopy layer suppressing weed germination and seedling emergence. Maize was superior in individual resource competition and became the dominant species, achieving effective weed control [48]. In niche theory, the large leaves and high ground-coverage of maize