Research > Soil Environmental Science

Cotton Cropping Systems

Conservation tillage, crop rotation, and cover crop management systems are evaluated under dryland and irrigated cropping systems. Continuous cotton systems provide a low residue system, thus incorporating crop rotation or cover crops can potentially improve soil function. We are evaluating conventional tillage, strip-tillage, no-till, and no-till with a terminated wheat cover crop in a long-term continuous cotton system (2018 begins 11th year). In addition, we are evaluating mixed species and single species cover crops in dryland cotton systems.

Findings

Under dryland and irrigated systems, cover crops result in significantly lower stored soil moisture during peak growth periods. However, stored soil moisture is generally more quickly restored under cover crop systems, and soil moisture is similar among all treatments by time of cotton planting.

During initial transition (first 3 years) to conservation tillage system, no-till systems resulted in higher net returns than conventional and strip-tillage under subsurface drip irrigation.

Lint yields have not been different over a four-year average between cover crop and no-cover crop treatments in dryland systems.

Net returns under dryland systems over the last four years were significantly lower as a result of mixed speices cover crop compared to no-till and conventional till without cover crops. No differences were observed among other cover crop treatments.

Lint yields and net returns have not differed between cover crop and non-cover crop treatments under pivot irrigation over a four-year average.

Legume cover crop species result in more available soil nitrate at time of cotton planting.

Wheat Cropping Systems

We are evaluating the impact of cover crops and double cropping in conservation wheat cropping systems. We are directly comparing cover crop and double crop systems on yields and soil properties. Species evaluated include grass/legume mixed species, cowpeas, mungbeans, sesbania, sunn hemp, guar, and pigeon pea.

We are also evaluating the effect of cover crop termination timing on stored soil moisture and crop yields. Three studies are being conducted on-farm. In addition, we are monitoring edge-of-field runoff quantity and quality from conventional, no-till, and no-till with mixed species cover crops.

Results

By time of wheat planting, differences in stored soil moisture are similar among early terminated cover crops, later terminated cover crops, and double crops IF fall precipitation occurs.

Initial results show that wheat yields are not different between double crop and cover crop systems, indicating a potential net economic return increase for double crop systems.

Cover crop systems have not resulted in a net soil C gain compared to double cropping or haying of mixed species summer crop.

No-till systems reduced soil erosion and increased infiltration rates compared to conventional tillage.

Irrigation Management

We are evaluating the synergies between irrigation management and conservation tillage systems. We are evaluating the effectiveness of conservation tillage to capture and store precipitation, and enhancing irrigation water use efficiency through strategic application timing. Irrigation is applied after crop establishment compared to delayed irrigation until initiation of flowering.

Results

Pre-watering or banking of water has not added value to irrigation water.

For 2015-2017 growing seasons, delayed irrigation has resulted in 42% less applied water than early season irrigation initiation while reducing cotton yields by 14%. Irrigation water use efficiency is significantly higher for “low” irrigation strategies.

Over five-year average (2013-2017) no-till systems (with and without cover crop) have resulted in significantly higher lint yields than conventional tillage and strip-till.

Past research has shown that most efficient irrigation is at deficit levels for cotton, sorghum, and guar.

Soil Organic Carbon and Soil Function

Soil organic carbon is often utilized to gauge the progression and/or success of a conservation tillage system. However, the soil ecosystem is quite diverse and use of a single parameter may be misleading. As a result, we measure soil organic carbon as well as other soil microbial, physical, and chemical properties.

These measurements have been made to existing studies described above as well as on-farm locations across the state of Texas, including the Blacklands, Rolling Plains, Southern High Plains, and High Plains.

Results

Soil organic carbon levels change very little with time, particularly in semi-arid environments.

Although soil organic carbon levels may see little change, other parameters such as soil strength and infiltration can be greatly impacted.

No-till systems can improve soil strength and infiltration. For cotton systems, incorporation of cover crops or a high residue rotational crop can significantly improve infiltration.

Cover crops have shown a trend to improve soil microbial activity and populations in wheat and cotton cropping systems.