Geographic Variation of Rice Yield Response to Past Climate Change in China

Previous studies demonstrated climate change had reduced rice yield in China, but the magnitude of the reduction and the spatial variations of the impact have remained in controversy to date. Based on a gridded daily weather dataset, we found there were obvious changes in temperatures, diurnal temperature range, and radiation during the rice-growing season from 1961 to 2010 in China. These changes resulted in a signiifcant decline of simulated national rice yield （simulated with CERES-Rice）, with a magnitude of 11.5%. However, changes in growing-season radiation and diurnal temperature range, not growing-season temperatures, contributed most to the simulated yield reduction, which conifrmed previous estimates by empirical studies. Yield responses to changes of the climatic variables varied across different rice production areas. In rice production areas with the mean growing-season temperature at 12-14＆#176;C and above 20＆#176;C, a 1＆#176;C growing-season warming decreased rice yield by roughly 4%. This decrease was partly attributed to increased heat stresses and shorter growth period under the warmer climate. In some rice areas of the southern China and the Yangtze River Basin where the rice growing-season temperature was greater than 20＆#176;C, decrease in the growing-season radiation partly interpreted the widespread yield decline of the simulation, suggesting the signiifcant negative contribution of recent global dimming on rice production in China＇s main rice areas. Whereas in the northern rice production areas with relatively low growing-season temperature, decrease of the diurnal temperature range was identiifed as the main climatic contributor for the decline of simulated rice yield, with larger decreasing magnitude under cooler areas.

Wheat Yield Response to Foliar Fungicide Application against Leaf Rust Caused by Puccinia triticina

A study was conducted on reducing the yield loss of wheat due to leaf rust caused by Puccinia triticina with foliar application of fungicides during the 2014-2015 and 2015-2016 growing seasons at the Wheat Research Institute in Faisalabad, Pakistan. Three fungicides： Folicur （tebuconazole） at 300 mL/ha, Nativo （tebuconazole ＋ trifloxystrobin） at 300 g/ha and Tilt （propiconazole） at 500 mL/ha were applied single or two times to Morocco and Sehar-06 wheat varieties used in the trial. The trial plots were first sprayed at the Zadok＇s scale （ZS） 3 stage and second sprayed between ZS 4.3 and 5.4 stages. The greenness of the trial crop was measured using GreenSeeker. Foliar application of fungicides significantly reduced the loss of grain yield and 1,000-grain weight （TGW） of wheat due to leaf rust in comparison to the control without fungicides application. Of the three fungicides, two times spray of Nativo reduced the grain yield loss of leaf rust susceptible mega wheat variety Sehar-06 by 45%-56% and the loss of TGW by 42%, also giving the highest marginal return in the trial. Single application of Nativo was equally effective as two times spray of Folicur in reducing the loss of wheat grain yield. Two times spray of Folicur was found to be the second choice of fungicide for reducing the yield loss of wheat. The research identified suitable fungicides for reducing the yield loss of wheat due to leaf rust and also generated important scientific knowledge required to manage a sudden outbreak of leaf rust to ensure food security.

Effect of Phopshate Fertilizer and Manure on Crop Yield, Soil P Accumulation, and the Environmental Risk Assessment

Phosphorus （P） applied from fertilizer and manure is important in increasing crop yield and soil fertility; however, excessive uses of phosphate fertilizer and manure may also increase P loss from agricultural soils, posing environmental impact. A long term experiment was conducted on a calcareous soil （meadow cinnamon） in Hebei Province, China, from 2003 to 2006 to investigate the effects of phosphate fertilizer and manure on the yield of Chinese cabbage, soil P accumulation, P sorption saturation, soluble P in runoff water, and P leaching. P fertilizer （P2O5） application at a rate of 360 kg ha^-1 or manure of 150 t ha^-1 significantly increased Chinese cabbage yield as compared to the unfertilized control. However, no significant yield response was found with excessive phosphate or manure application. Soil Olsen-P, soluble P, bioavailable P, the degree of phosphorus sorption saturation in top soil layer （0-20 cm）, and soluble P in runoff water increased significantly with the increase of phosphate fertilizer and manure application rates, whereas the maximum phosphorus sorption capacity （Qm） decreased with the phosphate fertilizer and manure application rates. Soil Olsen-P and soluble P also increased significantly in the sub soil layer （20-40 cm） with the high P fertilizer and manure rates. It indicates that excessive P application over crop demand can lead to a high environmental risk owing to the enrichment of soil Olsen-P, soluble P, bioavailable P, and the degree of phosphorus sorption saturation in agricultural soils.

Sunflower response to potassium fertilization and nutrient requirement estimation

Field experiments were conducted in oil and edible sunflower to study the effects of potassium(K) fertilization on achene yield and quality, and to estimate the nutrient internal efficiency(IE) and nutrient requirement in sunflower production. All trials in edible sunflower and 75% trials in oil sunflower showed positive yield responses to K fertilization. Compared with control without K fertilization, the application of K increased achene yield by an average of 406 kg ha–1for oil sunflower and 294 kg ha–1for edible sunflower. K application also increased 1 000-achene weight and kernel rate of both oil and edible sunflower. K fertilization improved the contents of oil, oleic acid, linoleic acid and linolenic acid in achenes of oil sunflower, and increased contents of oil, total unsaturated fatty acid and protein in achenes of edible sunflower. The average agronomic efficiency of K fertilizer was 4.0 for oil sunflower and 3.0 kg achene kg–1K2O for edible sunflower. The average IE of N, P and K under balanced NPK fertilization was 22.9, 82.8, and 9.9 kg kg–1for oil sunflower, and 27.3, 138.9, and 14.3 kg kg–1for edible sunflower. These values were equivalent to 45.5, 14.1, and 108.1 kg, and 39.0, 8.0, and 71.7 kg of N, P and K, respectively, in above-ground dry matter required for production per ton of achenes. The average harvest index of N, P and K was 0.47, 0.56 and 0.05 kg kg–1in oil sunflower, and 0.58, 0.58 and 0.14 kg kg–1in edible sunflower.

Temporal Patterns in Symptoms of Nitrogen Deficiency as Revealed by Remote Sensing of Corn Canopy

To evaluate the temporal patterns of N deficiencies in corn and assess the ability of remote sensing to diagnose N deficiencies during the vegetative growth of corn, three field-scale experiments were conducted with various rates (56, 112, and 168 kg N ha-1 ), timing (early and late applications) and placement (injected into soil and dribbled on soil surface) of N fertilization in a split-plot design. Relationships between canopy reflectance during the growing season and yield data at the end of growing season were studied for different treatments. Results showed significant variation in both grain yields and canopy reflectance among the three cornfields. The N fertilization made in early June resulted in low canopy reflectance in early July, but the differences disappeared as the season progressed. The effect of N rates on canopy reflectance was not significant in early July but it gradually became detectable in mid-July and thereafter. The fertilizer placement had a significant effect on grain yields only in one field but not on canopy reflectance in all three fields. These observations suggest that the deficiency of N developed under field conditions is a dynamic phenomenon, which adds complexity for accurately defining "N deficiency" and effectively developing management strategies for in-season correction. Remote sensing throughout the season helps collect information about important interactions that have not been given enough attention in the past.

Phosphorus Use Efficiency of Safflower （Carthamus tinctorius L.） and Sunflower （Helianthus annuus L.） Studied in Nutrient Solution

Safflower represents an important oil crop internationally and may have a production potential under low input conditions, but its putatively high phosphorous use efficiency is not sustained. This study aims to directly compare safflower with sunflower in terms of phosphorus use efficiency in nutrient solution under controlled conditions. Growth of both species responded strongly to increasing P supply. Safflower recovers less proportion of added P than sunflower. External P requirement （（g P supply （100 g dry matter （DM） produced）~） was higher in safflower than sunflower. The efficiency of the crops for DM production based on accumulated P （mg P potl, efficiency ratio）, and P concentration in DM （（mg P （g DM）＇I）, utilization index） were interpreted using Michaelis-Menten kinetics as growth response curves. Accordingly, Km constant was lower in sunflower compared to safflower in terms of utilization index, but both were similar in terms of efficiency ratio. High Km constant in safflower in terms of utilization index indicates the high P concentration in tissues to produce 50% of potential maximum DM, consequently less efficient crop. Utilization efficiency contributed more than uptake efficiency in overall PUE in the efficient cultivar and could be the cause of its superiority in PUE. It can be concluded that safflower has a high requirement for P with respect to growth, sunflower is more efficient in terms of uptake and utilization of P at optimal and sub-optimal P supplies indicating that safflower can not be considered a low nutrient input crop compared to sunflower with respect to phosphorus.

Quantifying extreme climatic conditions for maize production using RZWQM in Siping,Northeast China

Climate change has a great influence on agricultural production,especially under extreme climatic conditions.In this study,Root Zone Water Quality Model(RZWQM)was used to predict grain yields of maize in the Siping region,Jilin Province,Northeast China during the period from 1951 to 2015;and the response of grain yield to main climatic variables was qualitatively analyzed,especially in three special years of 1954,2000 and 2009.Results showed that 1℃ increase for minimum,maximum and mean air temperatures may produce 1224 kg/hm^(2),1860 kg/hm^(2) and 1540 kg/hm^(2) more grain yields,respectively,and seasonal rainfall amount of less than 450 mm,especially at the flowering and grain filling stages,greatly reduced grain yields.In the years of 1954,2000 and 2009,grain yields were reduced by 41%,47%and 40%compared to their mean value,respectively,correspondingly because of extra low temperature(lower by 2.1℃-2.3℃),less rainfall at the grain filling stage(36 mm)and extra high temperature(higher by 1.7℃-1.8℃),and less seasonal rainfall(252 mm).To reduce extreme climate’s effects on grain yield,it is suggested that supplementary irrigation at the flowering and grain filling stages should be provided when rainfall is much less at this stage and also appropriate maize species based on the longtime weather forecast should be selected.

Preliminary evaluation of a decision support tool for biochar amendment

Meta-analyses have shown that only about half of biochar addition studies report improved plant growth.To improve yield response,here we describe a decision support tool(DST)for selecting a biochar type and amendment rate to meet soil and crop management goals,based on soil and biochar tests values and crop requirements as reported by regional extension recommendations.Using data from a greenhouse wheat trial,we assessed whether this approach could predict changes in soil chemistry and whether it could identify soils in which amendment would stimulate crop yield.These data indicated that the DST could provide semi-quantitative predictions of biochar amendment rates needed to meet target soil pH levels,with recommended rates averaging 25%higher than were needed.The DST was better at predicting biochar application rates to provision P and K.Across six soil types,post-harvest measurements of extractable-K showed an average 104%recovery of the quantities estimated to be provisioned by conifer wood or wheat straw biochars.Extractable-P recovery averaged 101%in two sandy soils with low P-retention but was considerably lower in four soils with higher P-retention capacity.Green-house data also showed that wheat growth improved only when biochar alleviated pH that was substantially below critical thresholds for plant growth,and supported the principle of using crop-specific pH requirements as part of an approach for biochar decision-support.Future field trials that evaluate yield responses in several nutrient-deficient or acidified soils will be needed to provide a robust evaluation of this DST.