A study was conducted in 2005 and 2006 to evaluate the response of 10 rice cultivars to penoxsulam applied at 70 g ai/ha to two- to three-leaf rice. A related study was conducted in 2004 and 2005 to compare the rice response to applications of penoxsulam at 35 and 70 g/ha and bispyribac-sodium at 28 g ai/ha. In the first study, all 10 rice cultivars exhibited tolerance to penoxsulam as evidenced by plant height, number of days to 50% heading, and rice grain yield. In the second study, applications of both rates of penoxsulam and bispyribac-sodium reduced mass of rice roots 65 to 71% 2 wk after treatment compared with a nontreated control. However, rice grain yield was higher following application of penoxsulam at 70 g/ha compared with yield of the nontreated control or yield following penoxsulam at 35 g/ha and bispyribac-sodium. Rice recovered from injury observed following herbicide application with no negative impact on grain yield. Results indicate that, even though rice root injury can be severe following application, penoxsulam is safe for application to rice cultivars currently grown in the southern U.S. Rice Belt.

Water level declines in the Mississippi River Valley Alluvial Aquifer (MRVAA) are attributed largely to withdrawals for rice (Oryza sativa L.) irrigation. This study was performed to determine if alternative irrigation strategies for rice could reduce withdrawal from the MRVAA without having an adverse effect on yield and profitability. Research was conducted at 19 on‐farm locations across the Delta region of Mississippi from 2014 through 2016 to determine the effects of irrigation water management practice, i.e., conventional flood via cascade (CONV), multiple side inlet (MSI), and MSI coupled with alternate wetting and drying (AWD), on aquifer withdrawal, rough rice grain yield, irrigation water use efficiency (IWUE), and net returns above irrigation costs. Compared to CONV and MSI, up to 39% less water was applied to AWD (P ˂ .0001). Rice grain yield for AWD was not different from either CONV or MSI (P = .1343), despite substantial reductions in water use. Relative to standard irrigation strategies, AWD maintained or increased net returns up to $238 ha⁻¹ for pumping depths from 5.5 m to 122 m and diesel prices from $0.42 L⁻¹ to $0.98 L⁻¹ (P ≤ .0003). Irrigation water use efficiency was up to 59% greater for AWD relative to conventional systems due to the positive effects of the former on water use while maintaining yield (P = .0034). These data demonstrate that AWD can reduce withdrawal from the MRVAA while maintaining or improving yield and net returns relative to irrigation strategies currently employed across the midsouthern USA rice belt.

Glyphosate-resistant (GR) Italian ryegrass is one of the most troublesome weeds in Mississippi row crop production. Fall-applied residual herbicide applications are recommended for control of GR Italian ryegrass. However, carryover of residual herbicides applied in fields for rice production can have a negative impact on rice performance. Field studies were conducted in Stoneville, MS, to determine the effects of fall-applied residual herbicides on rice growth and yield. Herbicide treatments included suggested use rates (1×) of clomazone at 840 g ai ha^–1, pyroxasulfone 170 g ai ha^–1,S-metolachlor 1,420 g ai ha^–1, and trifluralin 1,680 g ai ha^–1, and two times (2×) the suggested use rates in the fall before rice seeding. Pooled across application rate, pyroxasulfone,S-metolachlor, and trifluralin injured rice to an extent 28% to 36% greater than clomazone 14 d after emergence (DAE). Rice seedling density and height 14 DAE and rice maturity were negatively affected by all fall-applied herbicides except clomazone. Applications at 2× rates reduced rough rice yields in plots treated with pyroxasulfone,S-metolachlor, and trifluralin compared with clomazone. Pyroxasulfone applied at the 2× rate reduced rough rice yield 22% compared with the 1× rate. Rough rice yield was 90% or greater of the nontreated control in plots treated with either rate ofS-metolachlor, and these were comparable with rough rice yields from plots treated with both rates of trifluralin and the 1× rate of pyroxasulfone. Early-season injury and reductions in seedling density and height 14 DAE, would preclude even 1× applications of pyroxasulfone,S-metolachlor, and trifluralin from being viable options for residual herbicide treatments targeting GR Italian ryegrass in the fall before rice seeding. Of the herbicides evaluated, only clomazone should be utilized as a fall-applied residual herbicide treatment targeting GR Italian ryegrass before seeding rice.

Core Ideas: Nitrogen applications increased soybean yields by 4% for sandy/silt loam soil. Nitrogen applications increased soybean yields by 8% for clay soil. Yield components response to N applications parallels the trends observed for yield. Nitrogen application is not an economically feasible way to improve soybean yield. Trials were conducted in 2014 and 2015 at Delta Research and Extension Center in Stoneville, MS, to evaluate soybean [Glycine max (L.) Merr.] response to N sources (ammonium sulfate [AMS], polymer‐coated urea [PCU], urea+urease inhibitor [Urea+NBPT, N‐(n‐butyl) thiophosphoric triamide]), N application rate (0, 45, 90, 135, 179 kg N ha⁻¹) and timing (V4, R1), on two soil textures (sandy/silt loam and clay) that are commonly used for soybean production in Mississippi. Urea+NBPT produced 5 and 8% greater aboveground biomass than AMS and PCU on sandy/silt loam soil. Nitrogen applications at the V4 growth stage resulted in 6% greater biomass production than the R1 application timing on sandy/silt loam. Averaged over N rates where a seed yield increase was observed, N applications increased soybean yields by 4% for sandy/silt loam soil and by 8% for clay soil compared to unfertilized soybeans. No differences were observed for soybean yields between N rates of 45, 90, 135, and 179 kg N ha⁻¹. Soybean yield from PCU was 2.5% greater than urea+NBPT on sandy/silt loam soil. Nitrogen rates influenced soybean yield components including pods and seeds plant⁻¹ on sandy/silt loam soil as well as seeds and seed mass plant⁻¹ on clay soil. Yield component response to N fertilization parallels the trends observed with overall soybean seed yield increases on both soil textures. Despite increases in seed yield observed with N application, analysis of partial returns suggests that N application is not an economically feasible way to improve soybean seed yield.