Phosphite (Phi)-containing products are marketed for their antifungal and nutritional value. Substantial evidence of the anti-fungal properties of Phi on a wide variety of plants has been documented. Although Phi is readily absorbed by plant leaves and/or roots, the plant response to Phi used as a phosphorus (P) source is variable. Negative effects of Phi on plant growth are commonly observed under P deficiency compared to near adequate plant P levels. Positive responses to Phi may be attributed to some level of fungal disease control. While only a few studies have provided evidence of Phi oxidation through cellular enzymes genetically controlled in plant cells, increasing evidence exists for the potential to manipulate plant genes to enhance oxidation of Phi to phosphate (Pi) in plants. Advances in genetic engineering to sustain growth and yield with Phi + Pi potentially provides a dual fertilization and weed control system. Further advances in genetic manipulation of plants to utilize Phi are warranted. Since Phi oxidation occurs slowly in soils, additional information is needed to characterize Phi oxidation kinetics under variable soil and environmental conditions.

Long-term no-till (NT) systems in the semiarid central Great Plains of the United States require flexible management strategies to minimize the impacts of herbicide resistant (HR) kochia (Kochia scoparia L.) and tumble windmill grass (Chloris verticillata Nutt.) as well as nutrient stratification on soil and crop productivity. This study examined strategic tillage (ST) to control HR weeds and improve crop yields in an otherwise long-term NT cropping system. Treatments were three crop rotations: (1) continuous winter wheat (Triticum aestivum L.) (WW); (2) wheat-fallow (WF); and (3) wheat-grain sorghum (Sorghum bicolor L.)-fallow (WSF); as main plots. Subplots were reduced tillage (RT), continuous NT, and ST of NT. Results showed ST and RT treatments provided significant control of HR weeds. Soil water content at wheat planting was significantly less with RT compared to NT or ST. Strategic tillage did not affect wheat or grain sorghum yields, but RT decreased sorghum yields by 15% compared to NT. Increasing cropping intensity reduced wheat yields. Strategic tillage reduced bulk density and had no effect on aggregate size distribution or mean weight diameter (MWD) compared to NT though RT reduced the proportion of large macroaggregates and MWD. Similarly, ST compared to NT had no effect on soil organic carbon (SOC) or nitrogen (N) concentrations. Soil phosphorus (P) was not different among the tillage treatments though RT increased potassium (K) concentration near the soil surface. The SOC, MWD, and micronutrient availability were greatest with WW though it had significantly lower pH and K concentration. Our results suggest ST could provide a mitigation option for HR weeds in NT systems with little impact on crop yields and soil properties.

Core Ideas: Average sorghum yield advantage was 120% for no tillage over conventional tillage and 55% for reduced tillage over conventional tillage. Average wheat yield advantage was 31% for no tillage over conventional tillage and 12% for reduced tillage over conventional tillage. Available soil water at planting in soil profile was less for conventional tillage than both no tillage and reduced tillage for both crops. There was a decline in wheat yield over time due to increased seasonal temperature. Tillage is among crop management factors that affect yield, profitability, and environmental quality. The objective of our study was to evaluate the effect of three long‐term tillage intensities; conventional tillage (CT), reduced tillage (RT), and no‐till (NT), on winter wheat (Triticum aestivum L.) and grain sorghum (Sorghum bicolor L.) yield, available soil water (ASW), and water productivity. The study was conducted near Tribune, KS, from 1991 through 2015 in a wheat–sorghum–fallow (WSF) rotation. The CT plots were tilled (primarily with a sweep plow), on average, four to five times per fallow season; NT plots used herbicides for weed control during fallow. The RT plots used a combination of herbicides and tillage for weed control during fallow prior to both crops for years 1991 to 2000; and, for the years 2001 to 2015, the RT system was NT before sorghum planting (short‐term NT) and CT before wheat planting. On average, there was a 31% wheat yield advantage for NT over CT, 16% NT over RT, and 12% RT over CT. On average, there was a 120% sorghum yield advantage for NT over CT, 41% NT over RT, and 55% RT over CT. Sorghum yields were 80% greater for continuous NT compared with short‐term NT (2001–2015 RT). The average of profile ASW at planting was less for CT compared with NT and RT. There was a significant yield and water productivity benefit in the order NT > RT > CT for both crops, but greater for sorghum than wheat.

Core Ideas: Grain yield of the second wheat crop was 80% of first wheat crop in WWSF. Grain yield of the second sorghum crop was 63% of first sorghum crop in WSSF. Four‐year rotations were similar in productivity to 3‐yr WSF. Water productivity was greater with 4‐yr rotations than continuous wheat. Continuous no‐till did not increase second year wheat and sorghum yields. Diverse crop rotations sustain crop productivity by increasing crop water productivity and improving soil structure. The objective of this study was to compare two 4‐yr winter wheat (Triticum aestivum L.) and grain sorghum (Sorghum bicolor L.) rotations in terms of grain yield, available soil water, and water productivity along with continuous winter wheat. A field study was conducted from 1996 through 2015 on a deep silt loam soil near Tribune, KS. The study consisted of three crop rotations: continuous annual wheat (WW), wheat–wheat–sorghum–fallow (WWSF), and wheat–sorghum–sorghum–fallow (WSSF). Grain yield, biomass, water productivity, and soil water were all greater for sorghum after wheat compared with sorghum after sorghum. Similarly, grain yield, biomass, water productivity, and soil water were all greater for wheat after fallow compared with wheat after wheat. The yield of the second wheat crop was 80% of the first wheat crop in WWSF, whereas the yield of a second sorghum was only 63% of the first sorghum crop in WSSF. The average crop water productivity (7 kg ha⁻¹ mm⁻¹) of the WSSF rotation was greater than the other rotations. On average, the WSSF system produced 2.05 Mg ha⁻¹ yr⁻¹ wheat equivalent yield (WEY), which was similar to the 1.96 Mg ha⁻¹ yr⁻¹ WEY from the WWSF rotation and greater than WW, which produced 1.53 Mg ha⁻¹ yr⁻¹ of wheat grain. A WSF rotation would have produced 2.0 Mg ha⁻¹ yr⁻¹ WEY, so the 4‐yr rotations were not more productive than a 3‐yr WSF rotation.

Core Ideas: Initiated in 1961, a 50‐yr field study quantified continuous irrigated corn response to annual N and P rates. Positive N–P interactions on grain yield and grain N/P concentrations were documented. Economic optimum N rate varied greatly over years, but averaged ∼175 kg N ha⁻¹ (1992‐2010). Significantly greater apparent fertilizer N recovery in grain (∼45%) occurred with P fertilization compared to no P (∼20%). Long‐term field studies can be used to improve nutrient effects on productivity. Long‐term agricultural field experiments provide valuable information regarding the effects of nutrient inputs on crop productivity. The objectives of this study were to quantify the effects of 50 yr of annual N and P application on irrigated continuous corn (Zea mays L.) grain yield, grain nutrient uptake, and economic optimum N rates. Six N (0, 45, 90, 134, 179, and 224 kg N ha⁻¹) and three P rates (0, 20, and 40 kg P ha⁻¹) in a factorial arrangement were applied annually from 1992 to 2010 to a Ulysses silt loam near Tribune, KS. From 1961 to 1991, only two P rates (0 and 20 kg P ha⁻¹) were applied with the six N rates. During the last 19 yr, grain yield increased 20% with P alone and 103% with N alone; however, N and P applied together increased grain yields up to 225% compared to the unfertilized control. The N rate required for maximum profit at 20 and 40 kg P ha⁻¹ averaged 172 and 180 kg N ha⁻¹, respectively. At the economic optimum N rate of 172 kg N ha⁻¹, apparent fertilizer nitrogen recovery in grain (AFNR_g) was 44% and apparent fertilizer phosphorus recovery (AFPR_g) was 63 and 44% with 20 and 40 kg P ha⁻¹, respectively. Fifty years of irrigated corn response to N and P fertilization demonstrated a strong positive interaction between N and P on grain yield, apparent N and P recovery, and profitability.