Very slightly differences on plant growth occurred within a range of weed control strips from 50 up to 150 cm, for both plant height and stem diameter, according to the adjusted regressions. In this sense, the results are in accordance with those ones presented above, so that the weed control should be performed within a range strip between 50 cm and 150 cm.Now, analyzing the growth pattern of rubber trees specifically at 360 DAP and 720 DAP, in function of crescent weed control strips, the best adjusted equation was also an exponential rising to maximum model, showing a high significance, normal distribution of residuals, and constant variance of residuals , being well-appropriated to describe the plant behavior and satisfying statistical conditions. We observed that all the growth characteristics increased when weed control strips was extended, reaching a maximum value and then keeping constant, as observed by RGR. In addition, at the ending of 360 DAP and 720 DAP, any weed control strip allowed rubber trees to grow more than in a total weedy situation, independently of the strip width.In spite of that,cannabis grow tray the determination of the strip width required to an effective weed control without permitting a significant plant growth reduction was dependent on growth characteristics evaluated.

In this sense, at the ending of 360 DAP, the best weed control strip for plant height and stem diameter development was within 150 cm;however the best strip for leaf area and above ground dry mass development was within 50 cm and 200 cm, respectively. In general, similar results were observed at the ending of 720 DAT, however the best strip for plant height and stem diameter development was within 100 cm , indicating a slight growth recovery of plants growing under weed control strips within 50 cm and 100 cm. So, we suppose that weed control within a strip of 100 cm is sufficient to prevent weed interference on the establishment of a rubber tree plantation.A reduction in the availability of moisture and nutrients leads to reduced tree growth and survival . In our study, rubber trees in the weedy plots suffered the most from weed competition, exhibiting comparatively poor growth and stem diameter reduction . That reduction also affected the development of the leaf area and the above ground dry mass accumulation, impacting negatively on the initial growth and establishment of rubber trees in the two years after plantation.No studies were found on rubber trees, but in South Africa, eucalyptus crown growth of 10 cm can be attained in 41 days with 20% weeding or in 66 days with 0% weeding . Little et al. used the tree crown diameter as an indication of tree performance.

They observed a distinct exponential increase in median crown diameter with weed-free strip width and concluded that a 2-m strip width with no weeding at all in the 1 m between rows proved to be the best management strategy.Although trees grown with weed-free strips produced the maximum heights and stem diameters in our experiment, completely weed-free plantation is rarely necessary for normal tree growth . Such regimes tend to be expensive to maintain in terms of herbicide usage. In addition, lack of ground flora may be deemed to be aesthetically poor and make the soil more susceptible to erosion and leaching . In our experiment, all other inter-row weedy options reduced tree height and stem diameter, but not to an unacceptable degree. However, it is important to control weeds, avoiding competition between plants, until canopy closure begins and trees start to dominate or suppress weed growth . Safflower is an annual oil seed crop well adapted to the semiarid regions of the US Great Plains and Canada. Safflower possesses a deep taproot system, which can extend to a depth of 2 to 3 m into the soil, and is more tolerant to drought stress compared to other oil seed and small grain crops. Therefore, safflower would be a potential fit as a second crop in the dry land winter wheat-fallow rotations in this region. In 2015, Montana ranked second among the safflower producing states, with 13% of the total US safflower production . In the absence of weed interference, safflower grain yields can exceed 2000 kg∙ha−1 when grown after winter wheat . However, safflower is a poor competitor with weeds, and weed control is one of the major production challenges for successful adoption of this crop.