Phosphorus is the second most important macronutrient after nitrogen and it has many vital functions in the life of plants. Most soils have a low available P content, which has become a key limiting factor for increasing crop production. Also, low P use efficiency (PUE) of crops in conjunction with excessive application of P fertilizers has resulted in serious environmental problems. Thus, dissecting the genetic architecture of crop PUE, mining related quantitative trait loci (QTL) and using molecular breeding methods to improve high PUE germplasm are of great significance and serve as an efficient approach for the development of sustainable agriculture. In this review, molecular and phenotypic characteristics of maize inbred lines with high PUE, related QTL and genes as well as low-P responses are summarized. Based on this, a breeding strategy applying genomic selection as the core, and integrating the existing genetic information and molecular breeding techniques is proposed for breeding high PUE maize inbred lines and hybrids.

Soil carbon dioxide emission (SCE) is known to be impacted by multiple factors including sources of respiration, environmental factors, and crop and soil management practices, yet few reports exist on how crop row position and growth stage affect SCE in sorghum [Sorghum bicolor (L.) Moench] fields. The objective of this study was to examine the effects of row position and growth stage on SCE dynamics in a field under grain and sweet sorghum production in northern Alabama. Soil CO 2 emissions were measured weekly during the growth period using a closed soil CO 2 survey chamber system. The results showed that SCEs increased steadily from approximately 4 μmol CO 2 m-2 s-1 during the vegetative stage and reached maximum values of approximately about 5 μmol CO 2 m-2 s-1 and 6 μmol CO 2 m-2 s-1 for grain sorghum and sweet sorghum, respectively. Soil CO 2 emissions then decreased to approximately 2 μmol CO 2 m-2 s-1 at the maturity and post-maturity periods for both sorghum types. Significant differences in SCE were observed between row positions. Soil CO 2 emissions at the row (R) positions were 19% greater than at interrow (I) positions during the entire growing season under grain sorghum production. Significant difference occurred only during the vegetative stage (SCE at R was 9% greater than at I position) under sweet sorghum production. Additionally, a significantly greater response of SCE to soil temperature (Ts) during the vegetative stage was observed under sweet sorghum production but not grain sorghum production. This study provides evidence that SCE is affected by row position, growth stage, and crop type and suggests that crop row position and growth stage should be taken into consideration for SCE estimation.

Weaning is a stressful event that affects animal welfare and performance. This study examined the effects of industrial hemp (Cannabis sativa) supplementation on behavior, chute score and physiological responses of cow-calf pairs during weaning. Ten apparently healthy Angus cow-calf pairs, average BCS of 6.0, were randomly allocated to one of two groups for 7 days: Control (CON, 200g/head of commercial grower feed, n=10) and Hemp (HMP, 200g/head containing 80% commercial grower feed containing 20% hemp, n=10), daily. Hay and water were provided ad libitum. Chute and exit scores were recorded and blood samples were collected at d 0, 4 and 7 of the feeding period. Animal activity data was recorded using automated activity monitoring systems Moomonitor and IceQubes for cows and calves, respectively. At weaning, cow-calf pairs were separated abruptly and observed. Data was analyzed using Stata 14.2. Overall, rectal temperature, respiratory rate, rumination duration, rumen fluid pH and activity did not differ (P > 0.05) between treatments. Specifically, hemogram and serum biochemistry results did not differ (P > 0.05) between cow groups. However, resting duration tended to be greater in HEMP compared with CON (383.94±19.3 vs 298.60±16.1 mins/day, P = 0.06) cows. In addition, feeding duration was greater in HEMP compared with CON (473.8±24.5 vs 262.3±31.6 min/day) cows. In calves, heart rate was lower in HEMP compared with CON (62.67 vs 94.7 beats/min, P = 0.03). Hemoglobin concentration was smaller in HEMP compared with CON (12.6 vs 14.1mg/mL, P = 0.02). However, mean corpuscular hemoglobin concentration was greater in HEMP compared with CON (33.04 vs 32.04g/dl, P = 0.04). We concluded that hemp supplementation increased resting and feeding duration of cows, and reduced heart rate of calves during weaning. This is the first report on the use of hemp to improve welfare of cow-calf pairs during weaning.