Influence of Wheat (Triticum aestivum) Straw Mulch and Metolachlor on Corn (Zea mays) Growth and Yield

Abstract

The presence of wheat straw mulch in no-tillage systems can increase corn yields in the central Great Plains, but information is needed on the optimal mulch level and the toxicity of metolachlor on corn growth. Research was conducted to determine the effect of winter wheat straw mulch levels of 0, 1.7, 3.4, 5.1, and 6.8 t ha–1and metolachlor rates of 0, 0.5, 1.0, and 1.5X-rates on corn growth and yield in a winter wheat-ecofallow-corn-fallow rotation at three locations across Nebraska. Response of corn to different mulch levels and metolachlor rates varied with climate and location. In general, early corn growth was retarded by increasing amounts of mulch due to reduced soil temperatures, but after tasseling corn grew taller under increasing mulch levels because of increased soil moisture. Soil water content, kernel moisture at harvest, stover dry matter, total dry matter, ears per plant, and kernel weight increased with increasing mulch level. Corn grain yield reached a maximum at a mulch level of 5.1 t ha–1. Kernel weight, kernel number, and grain yield increased with higher mulch levels and 0.5 and 1.0X metolachlor rates as weed competition was reduced, but decreased at the 1.5X-rate of metolachlor due to corn injury. Lack of sufficient growing degree-days to compensate for lower soil temperatures or corn injury reduced corn yields at the higher mulch levels and 1.5X-rate of metolachlor in west-central and western Nebraska. From a practical standpoint, a mulch level of 3.4 to 5.1 t ha–1and a metolachlor rate near the X-rate should increase corn yield (14 to 15%) over unmulched corn in the central Great Plains.

Weed dynamics and conservation agriculture principles: A review

“…Most agronomic crops and many weeds require soil temperatures above a certain threshold in order to germinate-lower average soil temperatures would therefore delay germination of both. This delayed germination and resulting shorter growing season of the crop can reduce yield, and it is emphasized that residue amounts should optimize yield rather than weed control (Wicks et al, 1994). Some weed species' germination is enhanced by larger temperature fluctuations (Liebman and Mohler, 2001); the buffered soil temperature could therefore reduce germination rates in addition to causing later germination.…”

“…In water-limited environments residue may promote weed seed germination while in wetter conditions it may have little effect (Teasdale and Mohler, 1993;Wicks et al, 1994;Vidal and Bauman, 1996). This is exemplified by studies where residue was less effective in suppressing weeds in drier sites or years (Buhler et al, 1996;Mashingaidze et al, 2012;Ngwira et al, 2014).…”

“…While 100% ground cover does not necessarily correspond to 100% light interception, it provides a useful proxy for estimating how much residue is needed to inhibit seedling growth. The amount varies by crop, with small grain crops requiring less (2-8 Mg ha −1 ) and large grains more (6-17 Mg ha −1 ; Greb, 1967;Teasdale et al, 1991;Wicks et al, 1994). For example, in a wheat-maize rotation study Crutchfield et al (1986) found that at least 3.4 Mg wheat straw ha −1 was needed in order to significantly reduce weed biomass, while in a monoculture maize system in Zimbabwe Ngwira et al (2014) found 6 Mg of maize stover ha −1 was needed.…”

“…Although crop residue can intercept herbicide, this does not necessarily translate to reduced weed control (Wicks et al, 1994;Derksen et al, 1995;Chauhan, 2013;Ngwira et al, 2014). Studies have shown that the weed suppression provided by surface residue more than compensates for reduced herbicide contact with weeds (Crutchfield et al, 1986;Derksen et al, 1995;Teasdale et al, 2003).…”

A cultural system to reduce weed interference in organic soybean

“…Because addition of new weed seeds was prevented during the 3-year interval, the contrast in emergence in the third year resulted from differences in seed survival over time. The second reason for weed suppression in soybean is that plant residue on the soil surface in no-till delays weed emergence and reduces establishment of seedlings 14,15 . This 2-year sequence of cool-season crops eliminated need for herbicides to control weeds in no-till soybean 11 ; however, herbicides controlled weeds during the interval between harvesting the cool-season crop and planting soybean.…”