Agronomy Journal最新文献

During symbiosis, C that rhizobia respire to power N fixation can be stored as polyhydroxybutyrate (PHB), shown to support rhizobia survival under laboratory starvation. We collected soil in 2015 from four replicate plots per treatment in two long-term experiments at Waseca, MN. Treatments differed in the intervals between soybean [Glycine max (L.) Merr.] hosts. We measured PHB accumulation in eight nodules per plant from four soybean (cv. MN0095) trap plants per soil sample. Trap plants were arranged in a greenhouse, common-garden experiment, and PHB accumulation was measured using flow cytometry. Treatments sampled after long intervals without soybean (greater than 2 years) showed a greater relative abundance of high-PHB strains. Treatments sampled after the first year of soybean following 5 years of a non-host crop showed a decreased relative abundance of high-PHB strains, compared to treatments sampled after long intervals without soybean. The latter result is consistent with the hypothesis (not tested directly here) that some high-PHB strains were “sanctioned” by plants as less beneficial. Our results suggest that rhizobia strains with the tendency to allocate more C to N fixation at the expense of PHB accumulation may be less likely to persist where soybean is grown infrequently or where soil conditions make PHB particularly valuable. However, with typical 2-year rotations in Minnesota, differences in PHB storage are unlikely to have a major effect on the relative survival of strains.

Composts are increasingly used to enhance soil health and agricultural sustainability, but their impacts on nitrogen (N) availability are unclear. In a 3-year field experiment with subsurface drip-irrigated tomatoes (Solanum lycopersicum), we investigated the effects of food waste and green waste co-compost (FW) and green waste compost (GW) on yield, nitrogen-use efficiency (NUE), nitrate leaching potential, and fertilizer N retention. Various combinations of compost rates (0, 9, or 18 t ha⁻¹) and fertilizer N levels (0%, 70%, 85%, and 100% of the recommended rate) were examined, and ¹⁵N-labeled fertilizer was used. In Years 2 and 3, FW and GW either maintained or increased crop yield compared to no compost when 0% or 70% N was applied; however, lower NUE was observed in the compost treatments compared to no compost when 70% or 85% N was supplied. Postharvest, FW showed greater fertilizer N retention in topsoil than GW and controls, while no difference in nitrate leaching potential was found among treatments, except for Year 2 during which FW exhibited the lowest potential. These results suggest that compost can immobilize fertilizer N, reducing its uptake by crops but enhancing soil retention, potentially acting as an N source or a primer of soil N mineralization. Future research is needed to assess compost's impact on N gaseous emissions and distinguish its dual roles as an N source and a soil N mineralization primer. This is essential for developing nutrient management guidelines to minimize N losses.

Grazed pastures supporting ruminant livestock have not been well characterized for soil health condition. However, growing interest in holistic management of compromised watersheds suggests that grazing lands deserve more attention for their capacity to provide ecosystem services. Relatively little is known about how grazing management affects soil aggregation and other surface-soil properties on private lands in the eastern United States. This study investigated the effects of land use (conventional-till cropland, no-till cropland, grassland, and woodland) and pasture management characteristics on soil aggregation, bulk density, sieved soil density, total soil N, and soil-test biological activity on 31 private farms distributed across the western half of Virginia. Soil stability index followed the order (p < 0.05): conventional-till cropland (0.60 mm mm⁻¹) < no-till cropland (0.78 mm mm⁻¹) < woodland (0.85 mm mm⁻¹) = grassland (0.89 mm mm⁻¹). Surface soil characteristics improved with pasture age due to organic matter recycling from residual forage mass and animal excreta. Increases in total soil N and soil-test biological activity helped create water-stable aggregation and reduce soil bulk density. Soil stability index was optimized with moderate stocking rate of 0.5–1.1 Mg live weight ha⁻¹. Stocking method did not affect soil aggregation or bulk density. Soil stability index declined with increasing N fertilization rate. Soil aggregation characteristics were generally not affected by organic amendment, quantity of hay fed on farm, or occasional hay harvest from pastures, likely because aggregation was high across management variables. Well-managed grazed pastures in Virginia are creating desirable conservation agricultural land uses to protect watershed quality.

Ranking the contribution of genotype, environment, and management (G × E × M) on maize's economic optimum nitrogen fertilizer rate (EONR) variability could improve understanding and predictability of EONR. We performed a simulation experiment using the Agricultural Production Systems sIMulator model with the objectives to (1) rank the effects of 24 individual G × E × M factors on the magnitude and interannual variability of the EONR across the US Midwest and (2) investigate the impact of G × M factors on the EONR variability under present and future climate scenarios. Results indicate that genetics (27%), management (31%), and environmental conditions (41%) each influence the EONR variability. Within these broad categories, the top three individual factors impacting the EONR were interannual weather variability, crop radiation use efficiency, and the soil inorganic N carryover from the previous year. The G × E × M factors influenced the yield response to N fertilizer in different ways. Soil-related factors (e.g., organic matter and residual nitrate) influenced grain yields at the low N rates, while management factors (e.g., planting date and density) influenced yield at all N rates. Combining increases in plant density and changes in genetics synergistically increased the EONR by 15% from baseline. Future climate scenarios without adaptation decreased the EONR and yield loss, but crop adaptation was buffered against the negative climate change impacts. We concluded that 59% of the annual EONR variability is manageable (due to genetics and management) and that G × M factors could buffer climate change's negative effects on crop production. Present results can inform experimental research on N fertilizer and N rate decisions.

In recent years, water conservation efforts in rice production have necessitated the use of reduced irrigation input systems such as alternate wetting and drying (AWD) as a substitute to conventional continuous flood-irrigated systems (FLD), but little is known about the role of AWD in altering outcrossing potentials between cultivated rice and weedy rice (WR). In the United States, rice growers often control WR by cultivating varieties that possess herbicide resistance. However, an ongoing concern with such technology is hybridization or outcrossing between herbicide-resistant rice cultivars and WR over time. Such outcrossing may result in transferring of herbicide resistance with increased occurrence of herbicide-resistant WR ecotypes and reduction in the efficacy of herbicide management. This study compared and quantified outcrossing rates between two Clearfield rice varieties (CL142AR and CL261) that are herbicide resistant and two common WR genotypes, strawhull (SH) and blackhull (BH), under FLD and AWD management. Outcrossing was evident in all four genotype combinations (i.e., CL142AR or CL261 cultivated rice and SH or BH weedy rice) in both FLD and AWD; however, outcrossing rates with CL261 averaged about 6.5 times lower than those with CL142AR. Additional analysis revealed that higher outcrossing rates were associated with increased synchrony of flowering times and closer vertical proximity of panicles of WR to CL142AR than with CL261. AWD irrigation reduced outcrossing in SH weedy rice, suggesting that reduced outcrossing of SH weedy rice might be an additional benefit from AWD irrigation management.

Intercropping perennial forage grasses into cereal crops is an alternative to recover degraded pastures. However, the intercrop of forage grasses, such as Urochloa ruziziensis (R. Germ. and C. M. Evard) Crins (Congo grass), can lead to losses in cereal yield. Therefore, it is necessary to develop management strategies that allow forage grass establishment without major losses in cereal yield in intercropping. The objective was to study the agronomic and economic impacts of intercropping U. ruziziensis into a Clearfield upland rice (Oryza sativa L.) cultivar in the state of Goiás, Brazil, in two growing seasons. Treatments included forage grass seeds sowing method (broadcast or incorporation to the soil) and sowing times (at rice sowing, 20 days after emergence [DAE], and 45 DAE of rice). Also, imazapyr + imazapic herbicide was applied to restrict the competitive effect on rice yield. Monocropping control plots were also evaluated. Grain yield was measured on rice. Forage grass dry matter yield was measured at 30, 60, and 90 days after harvesting (DAH) of rice. Crude protein content was analyzed at 90 DAH. Profitability was calculated for each cropping system relative to rice monocropping. Intercropping of rice and U. ruziziensis sowed at 45 DAE provided the highest grain yield relative to other assessed intercropping treatments as well as rice monocropping. Concurrent sowing of rice and incorporated U. ruziziensis seeding provided the greatest economic return. This reformed cropping system improved land and pasture output, which can reduce the pressure to convert more land to agricultural use.

Reproductive development of rice (Oryza sativa L.) is critical for obtaining high yield by promoting fertilization at the flowering stage. However, limited information is available about historical changes in anther and stigma morphology during breeding programs; these characteristics contribute strongly to a cultivar's abiotic stress resistance. We tested the hypothesis that genetic progress for culm length during breeding has affected the floral morphology of rice cultivars released in Japan. We used field trials in 2 years in northern Japan to quantify anther and stigma morphology and culm length for rice from 147 cultivars (2020) and 284 cultivars (2021) that had been released from 1902 to 2011 (109 years) in Japan under two nitrogen (N) regimes (no-N and high-N). Culm length significantly decreased over time at a rate of 1.9–3.1 cm per 10 years at low N. However, anther length, anther width, and stigma length showed no consistent trend during the period. High N significantly increased culm length of most cultivars by an average of 21%–26% but tended to shorten anther length by 2%–3% and anther width by 1%–2% on average and increased stigma length by only 1%, with large variation among cultivars. Our results suggested no evidence on positive breeding efforts targeting on floral morphology to improve abiotic stress tolerance and yield in contract with culm length.

Safflower (Carthamus tinctorius L.) is an edible oilseed crop mainly cultivated in marginal lands. This study evaluates safflower crop water requirements to understand its feasibility to cultivate under rainfed ecosystem through a field experiment undertaken at the International Crops Research Institute for the Semiarid Tropics research farm, India. Eight improved and stress-tolerant safflower cultivars (five spiny and three non-spiny) were evaluated in Vertisols at three soil depths, that is, shallow: <0.60 m, medium: 0.60–1.20 m, and deep:1.20–1.80 m, over 3 years (2009–2012). Wet, normal, and deficit rainfall years were experienced during 2009/2010, 2010/2011, and 2011/2012, respectively. Soil moisture, crop yield, and growth parameters were measured, and field-scale hydrology was captured through a calibrated one-dimensional water balance model. Safflower responded to available residual soil moisture which varied with soil depth and rainfall received in different years. Total crop water use was 300–320 mm during the postrainy season, of which about 70% was extracted in deep Vertisols and 55% in medium Vertisols through residual soil moisture. In addition, 30% of water requirement was met through postrainy season rainfall. Safflower grown in shallow Vertisols could only meet 40% of crop water requirement. Spiny cultivar NARI-H-15 grown in deep soil recorded a maximum yield of 1890 kg ha⁻¹ in the wet year. Seed yield from spiny cultivars grown in deep and medium soils was nearly similar (1500–1600 kg ha⁻¹) during wet and normal years; a significant reduction in yield (>50%) occurred in shallow soils and also during a rainfall deficit year. Spiny cultivars produced 10%–50% higher seed yield compared to non-spiny cultivars. Growing safflower in medium and deep Vertisols provides opportunities for crop intensification.

Starter N fertilization at low rates may enhance pea (Pisum sativum L.) performance, but little information exists about the effect of N fertilization rate to previous crop (NRPC) on pea growth, yield, and quality in small grain–pea rotations. We examined the effect of N fertilization rates to barley (Hordeum vulgare L.) and spring wheat (Triticum aestivum L.) on succeeding pea growth, yield, and quality in barley–pea and spring wheat–pea rotations from 2006 to 2019 in the semiarid environment of US northern Great Plains. We measured pea plant density, straw and grain yields, harvest index, straw N concentration, grain protein concentration, grain test weight, straw and grain N uptake, and N harvest index. In the barley–pea rotation, pea grain yield increased with increased NRPC. Grain test weight was greater without than with NRPC in 2008 and 2009. In the spring wheat–pea rotation, straw yield was greater for 50 than 0 kg N ha⁻¹ of NRPC in 2014, 2018, and 2019. Grain yield and N uptake were greater with than without NRPC in 2014, 2015, and 2019, but grain test weight varied with NRPC and year. Plant density, harvest index, straw N concentration, grain protein concentration, straw N uptake, and N harvest index varied with year in both barley–pea and spring wheat–pea rotations. Nitrogen fertilization to barley or spring wheat can enhance succeeding pea grain yield and N uptake during years with normal growing season precipitation in barley–pea and spring–wheat pea rotations in the semiarid region of the US northern Great Plains.

Nitrogen (N) fertilizer applications near the time of planting are important for upper US Midwest corn (Zea mays L.) production, but wet springs may result in significant N losses. Split applications may circumvent this problem and improve fertilizer uptake and use efficiency, but the relative contribution of N from the soil and fertilizer is poorly understood. A field study with six sites in Minnesota received ¹⁵N-labeled urea fertilizer in the first year and unlabeled urea in the second year to determine the effect of N rate and application timing on corn uptake and accumulation patterns of fertilizer-derived N (FDN) and soil-derived N (SDN) over two consecutive growing seasons. Corn responded positively to fertilization. The percentage of total N uptake as FDN was greatest closest to the time of application but decreased over time as SDN became the dominant N source. A split application (45 kg N ha⁻¹ at planting, 90 kg N ha⁻¹ at V4) significantly improved FDN uptake over the 135 kg N ha⁻¹ preplant treatment but did not improve total N uptake in the first year at any site. Fertilizer-N use efficiency (F¹⁵NUE) using the isotopic method was 2.8%–43.3% across all sites at the end of the first year with the majority partitioned to the grain. At the end of the second year, approximately 2.2% of the first-year applied FDN was recovered in aboveground biomass. Fertilization ensures adequate N availability to the developing crop, but ultimately SDN contributed ≥61% of the total N uptake.