Tuber initiation and development in irrigated and non-irrigated potatoes

Tuber initiation and development are processes basic to potato production and are particularly critical in areas with short growing seasons. It is important to know how and to what extent management decisions affect these processes in order to maximize the yield of marketable tubers. A two-year field study, conducted in southcentral Alaska, examined top growth, tuber initiation, and tuber development in eight potato cultivars grown with and without irrigation. Plants of the cultivars Allagash Russet, Bake-King, Green Mountain, Kennebec, Lemhi Russet, Russet Burbank, Shepody, and Superior were harvested weekly throughout the growing season, and top dry weight, numbers of tubers, and individual tuber fresh weights were recorded. Top dry weight was reduced by moisture stress shortly after emergence in 1993, and about one month following emergence in 1994, when early-season soil moisture was greater. The weight of tubers was similarly affected within approximately 5 wk of emergence in 1993 and 6 weeks in 1994. Tuber weight at harvest was increased two-to three-fold by irrigation in all cultivars. The number of tubers each plant set was affected by irrigation in most, but not all, cultivars. Some varieties (Lemhi Russet in 1994, Allagash Russet both years) set more tubers than were maintained through the growing season. Tuber remnants found during sample collection indicated that tuber reabsorption had occurred. Irrigated Green Mountain had more than one tuber initiation period during the season, whereas other varieties such as Shepody maintained a relatively constant number of tubers following initial tuber set. Tuber size distribution at the end of the growing season showed that larger tubers were favored by irrigation.     

Placement of soil moisture sensors in sprinkler irrigated potatoes

Potato (Solanum tuberosum L.) is particularly sensitive to soil water potential below ?50 to ?60 J kg^?1 during tuber development. Soil water must also be carefully monitored to irrigate efficiently and to minimize nitrate leaching associated with over-irrigation. Water distribution in and below potato hills during and following sprinkler irrigation was monitored using granular matrix sensors (Watermark Model 200, Irrometer Co., Riverside, CA) placed in 0.10 m × 0.15 m cross-sectional grids down to 0.6-m depth below the soil surface. Each grid consisted of 26 sensors. Sensor electrical resistance had been calibrated to soil water potential. During one test, soil water potential was intentionally lowered to levels drier than ideal for potato to emphasize soil wetting and drying patterns. Over the 26 locations in the grids, the soil water potential averaged ?33 J kg^?1 over a six week period, with sprinkler irrigations evenly rewetting the upper 0.2 m of the hill. On average, the driest locations were the top of the hill, directly under the hill, and below the furrow with wheel track compaction. Ideal sensor locations for monitoring soil water status and scheduling irrigations are offset 0.15 m from the center of the hill and 0.1 to 0.2 m deep. Sensors installed in silt loam soil responded within four hours to wetting and within 12 hours to drying, the shortest increments of time measured.     

Evaluation and interpretation of the crop water stress index for well-watered potatoes

During the 1988, 1989 and 1990 growing seasons, canopy and air temperatures, solar and net radiation, relative humidity and wind speed were measured at 10 minute intervals during daytime hours in a field of wellwatered Russet Burbank potatoes in southeast Idaho. A linear relationship between canopy temperature minus air temperature and vapor pressure deficit (T_C-T_A = 0.2 -2.0 VPD) was developed for use in the Crop Water Stress Index (CWSI). Values of CWSI for well-watered potatoes were generally in the -0.4 to 0.4 range, and exhibited a diurnal trend of decreasing values towards midday and increasing values during the afternoon. Wind speed appeared to increase the CWSI and may account for some of the observed variability.     

The effect of crop rotations on Rhizoctonia disease of potatoes

Since 1964, replicated rotation plots in Presque Isle, Maine have continually been planted and evaluated to determine the effect of various rotation crops on tuber appearance, quality, and yield. In 1974 and 1975, the saprophytic activity ofRhizoctonia solani in the soils of each rotation combination was determined, and the tubers harvested were scored forRhizoctonia damage. Soils with a two-year rotation of oat-potato had the lowest amount of saprophytic activity byRhizoctonia and provided the lowest incidence of disease on the stems, roots, and tubers of the cultivars Kennebec and Katahdin. With the cultivar Russet Burbank, the three-year rotations generally provided the lowest incidence of disease; however, this cultivar is more susceptible to the pathogen. The plots of potatoes that were not rotated had the highest pathogen activity and the greatest disease incidence.     

Diverse no-till irrigated crop rotations instead of burning and plowing continuous wheat

Field burning of residue is a traditional management tool for irrigated wheat (Triticum aestivum L.) production in the Inland Pacific Northwest of the United States (PNW) that can result in reduced air quality. A 6-year no-till field experiment to evaluate two complete cycles of a 3-year irrigated crop rotation of winter wheat–spring barley (Hordeum vulgare L.)–winter canola (Brassica napus L.) was sown (i) directly into standing residue of the previous crop, (ii) after mechanical removal of residue and, (iii) after burning of residue. The traditional practice of continuous annual winter wheat sown after burning residue and inverting the topsoil with a moldboard plow was included as a check treatment. Over-winter precipitation storage efficiency (PSE) was markedly improved when residue was not burned or burned and plowed after grain harvest. Grain yield of winter wheat trended higher in all no-till residue management treatments compared to the check treatment. Average grain yields of spring barley and canola were not significantly different among the no-till residue management treatments. Winter canola failed in 5 of 6 years due to a combination of a newly identified Rhizoctonia damping-off disease caused by Rhizoctonia solani AG-2-1 and cold temperatures that necessitated replanting to spring canola. Six-year average net returns over total costs were statistically equal over all four systems. All systems lost from $358 to $396 ha^?1. Soil organic carbon (SOC) increased linearly each year with no-till at the 0–5 cm depth and accumulated at a slower rate at the 5–10 cm depth. Take-all of wheat caused by Gaeumannomyces graminis var. tritici was most severe in continuous annual winter wheat. The incidence and severity of Rhizoctonia on roots of wheat and inoculum of R. solani AG-8, was highest in the no-till treatments, but there was no grain yield loss due to this disease in any treatment. Residue management method had no consistent effect on Rhizoctonia root rot on barley. The annual winter grass downy brome (Bromus tectorum L.) was problematic for winter wheat in the standing and mechanically removed residue treatments, but was controlled in the no-till residue burned and the burn and plow check. Another winter annual grass weed, rattail fescue (Vulpia myuros L.), infested all no-till treatments. This was the first comprehensive and multidisciplinary no-till irrigated crop rotation study conducted in the Pacific Northwest.     

Using pattern recognition for estimating cultivar coefficients of a crop simulation model

The introduction of a new cultivar in a process-based crop simulation model requires the estimation of cultivar coefficients that define its growth and development characteristics. An accurate estimation of these coefficients requires replicated field experiments that, in many cases, are not available to crop model users. The objective of this study was to employ a pattern recognition approach to estimate cultivar coefficients from a minimum set of experimental data for use with a crop simulation model. The pattern recognition approach is based on similarity measures. Its main goal is to classify groups of data or patterns based on either a priori knowledge or on statistical information extracted from the patterns. Based on the similarity measure as the central calculation of the pattern recognition approach, the algorithm searches the space of features of other cultivars in the database to find the most similar cultivar as the best match to the target cultivar. The approach of this study was based on a few key characteristics of maize crop growth and development, including anthesis and harvest maturity dates, maximum leaf area index (LAI_max), final above ground biomass, and grain yield, which were used as the features vector. To construct the feature database, 27,789 hypothetical cultivars were constructed by combining different values of the six cultivar coefficients of the Cropping System Model (CSM)-CERES-Maize. Experiments performed in Florida (FL) and Iowa (IA) USA, Spain, central Punjab, Pakistan, and in Piracicaba, SP, Brazil were selected and later modified to provide a full potential production environment. The crop model was run for potential production for all 27,789 hypothetical cultivars and the outputs of these simulations were used as the feature database. For evaluation of this approach, we used the features for 29 different maize cultivars as reported from field experiments that are available in DSSAT maize cultivar database and also for four additional cultivars of which two had not been used in any aspect of this study. The model was run for all 33 cultivars, using the best match cultivar coefficients, for the conditions of the three study sites and locations where the latter four cultivars have been grown. The simulated crop characteristics were compared with the same simulated crop characteristics based on the original coefficients used to run the simulation model. We found that the approach based on pattern recognition was able to estimate the cultivar coefficients with a reasonable accuracy. The coefficient of determination (r²), root mean square difference (RMSD), and relative root mean square of difference (RMSDr) confirmed that this approach provided reliable estimates for the maize cultivar coefficients. The highest R² (0.98) was obtained for anthesis in Florida and the lowest (0.57) was obtained for grain yield in Spain. The highest RMSD (8.8) was obtained for maturity in Spain, while the lowest RMSD (1.1) was obtained for aboveground biomass in Florida. Although the values for RMSD were different across the different sites, this approach provided a level of accuracy that might be acceptable, especially for users who only have one year of experimental data and demand the best possible initial guess for the coefficients of their specific cultivar. This approach has been implemented in a simple tool that can be easily applied by users of DSSAT and the CSM-CERES-Maize model.     

Changes and determining factors of crop evapotranspiration derived from satellite-based dual crop coefficients in North China Plain

Evaluating actual crop evapotranspiration(ET_c) variations and their determining factors under changing climates is crucial for agricultural irrigation management and crop productivity improvement in nonhumid regions.This study analyzed the spatiotemporal characteristics and detected the determining factors of ET_c for winter wheat and summer maize rotation system from 2000 to 2017 in the North China Plain(NCP),by combining the FAO-56 dual crop coefficient approach with remot...     

Growth of the whole root system for a plant crop of sugarcane under rainfed and irrigated environments in Brazil

Sugarcane crops are managed over 8 million hectares in Brazil and future extensions might occur on less favorable lands where irrigation would be necessary to increase and stabilize yields. Root growth was studied by sequential soil coring under rainfed and irrigated conditions for one cultivar widely planted in Brazil. Root length densities (RLD) were measured 34, 49, 125, 179, 241 and 322 days after planting (DAP) down to a depth of 1 m. At the harvest (332 DAP), root intersects (a proxy for RLD) were counted on two vertical trench walls in each water supply regime, down to a depth of 6.0 m. The highest RLD in deep layers (below a depth of 0.6 m) were observed in the rainfed crop from 125 DAP onwards. By contrast, the highest RLD in the upper layers during dry periods were found in the irrigated crop. The maximum depth reached by roots at the harvest was little affected by irrigation: 4.70 m and 4.25 m in the rainfed and irrigated crop, respectively. About 50% of root intersects were observed below the depth of 1 m in the two water supply regimes. This pattern suggested a strong genetic control of root growth in deep soil layers. The total amount of root intersects 332 DAP was 49% higher in the rainfed crop than in the irrigated crop, and root distribution was more homogeneous. Mean root front velocity was about 0.5 cm day⁻¹ the first 4 months after planting and increased thereafter up to the end of the harvest (1.86 cm day⁻¹ and 1.75 cm day⁻¹ on average in the rainfed and the irrigated crops, respectively). Our study pointed out the necessity to take into account the development of sugarcane roots in deep soil layers to improve our understanding of net primary production control by water availability.     

冀东滦下灌区种植结构调整策略的研究

分析了冀东滦下灌区四县稻田土壤耕层的全盐含量和地下水矿化度,并依据我国盐渍土壤划分标准和不同作物的耐盐能力,将该稻区划分为宜稻区、盐生植物种植区、耐盐作物种植区和大田旱作物种植区,并提出了各个区域的种植技术方案及配套的工程技术措施。     

Simulation of salt and water movement and estimation of water productivity of rice crop irrigated with saline water

The HYDRUS-ID model was experimentally tested for water balance and salt build up in soil under rice crop irrigated with different salinity water (ECiw) of 0.4, 2, 4, 6, 8 and 10 dS m⁻¹ in micro-lysimeters filled with sandy loam soil. Differences of means between measured (M) and HYDRUS-1D predicted (P) values of bottom flux (Q _o) and leachate EC as tested by paired t test were not found significant at P = 0.05 and a close agreement between RMSE values showed the applicability of the HYDRUS-1D to simulate percolation and salt concentration in the micro-lysimeters under rice crop. Potential ET values of rice as obtained from CROPWAT matched well with model predicted and measured one at all ECiw treatments. The model predicted root water uptake varied from 66.1 to 652.7 mm and the maximum daily salt concentration in the root zone was 0.46, 2.3, 4.5, 6.7, 8.4 and 10.2 me cm⁻³ in 0.4, 2, 4, 6, 8 and 10 dS m⁻¹ ECiw treatments, respectively. The grain production per unit evapotranspiration ( \textWP_{\textET\texta} {\text{WP}}_{{{\text{ET}}_{\text{a}} }} ) value of 2.56 in ECiw of 0.4 dS m⁻¹ treatment declined to 1.31 with ECiw of 2 dS m⁻¹. The \textWP_{\textET\texta} {\text{WP}}_{{{\text{ET}}_{\text{a}} }} reduced to one-fifth when percolation was included in the productivity determination. Similarly, the water productivity in respect of total dry matter production (TDM) was also reduced in different treatments. Therefore, the model predicted values of water balance can be effectively utilized to calculate the water productivity of rice crop.