Response Of Grain Yield Research Articles

Impact of Nitrogen Rate on Maize Yield and Nitrogen Use Efficiencies in Northeast China

Optimizing N fertilization is important to improve both maize (Zea maysL.) yield and nitrogen use efficiencies (NUEs). A 3‐yr maize field experiment (2008–2010) was conducted to evaluate the response of grain yield, aboveground biomass, plant N concentration, N uptake, and NUEs to fertilizer N rates from 0 to 280 kg N ha−1at three different rain‐fed Haplic Phaeozem soils (FAO classification) in Northeast China. When N application rate increased from 70 to 280 kg N ha−1across all site‐years, N recovery efficiency, N agronomic efficiency, N internal efficiency and N partial factor productivity decreased from 76.5 to 9.0%, 25.3 to 0.1 kg kg−1, 70.7 to 40.8 kg kg−1, and 145.6 to 22.8 kg kg−1, respectively. Differences observed among the years and experimental sites were primarily caused by variability in rainfall and soil characteristics. The maximal grain yield of 11.0 Mg ha−1was achieved at an N rate of 210 kg N ha−1with normal rainfall. Nitrogen application beyond the optimal N rate did not consistently increase grain yield, and caused a decrease in NUEs. The range of optimal N rate for maize grain yield fell between 140 and 210 kg N ha−1at the three sites from 2008 to 2010 in Northeast China based on the best fitted models (quadratic, linear plus plateau, and quadratic plus plateau). The results provide guidelines for selecting N application rates to optimize both maize yield and NUEs in Northeast China.

Effect of soil pH and crop sequence on the response of wheat (Triticum aestivum) to phosphorus fertiliser

Changes in soil fertility following long periods of crop production in the south-west of Western Australia (WA) may have implications for phosphorus (P) fertiliser recommendations for wheat production. When the sandy soils of the region were first cleared for agricultural production, they were typically marginally acidic to neutral, with soil extractable-P levels inadequate for crop production. Recent surveys have shown that 87% of soils in south-west WA exceed the critical soil extractable-P level required for 90% of maximum grain yield, and ~70% of soils have a surface-soil pHCa <5.5. There has also been a shift towards a high frequency of wheat in the crop sequence. We conducted a field experiment to begin to quantify the importance of the interactions between soil pH and crop sequence on wheat response to P fertiliser. For grain yield, the magnitude of the response was greatest for rate of P applied, followed by lime treatment and then crop sequence. There were no interactions between these treatments. Our analysis of the grain-yield response to rates of P fertiliser showed no significant difference between the shape of the grain-yield response curve for treatments with and without lime. However, we did find a significant interaction between lime treatment and rate of P fertiliser applied for shoot P concentration and that soil P was more plant-available in the +lime than the –lime treatment. There is justification for making realistic adjustments to yield potential based on soil pH or crop sequence, although further work is required to determine whether the shape of the grain-yield response curve varies with these two factors.

Early and Late Maturing Grain Sorghum under Variable Climatic Conditions in the Texas High Plains

Abstract. In the Texas High Plains, variable climatic conditions prevail between and within growing seasons. As this area continues to experience drought conditions and water resources for irrigation become more limited, sorghum [Sorghum bicolor (L.) Moench] production may become a more popular choice to sustain profitable crop water productivity with limited water. Regional sorghum production functions are helpful in strategizing adaptation methods for coping with climatic variability, but new varieties often exhibit new production functions. This article compares sorghum responses of grain yield, evapotranspiration (ET), water use efficiency (WUE), and irrigation water use efficiency (IWUE) of a late maturing (LM) and early maturing (EM) hybrid during three recent growing years exhibiting climatic variability (2009-2011). The hybrids were irrigated at levels of 80%, 55%, 30%, and 0% replenishment of soil water depletion to field capacity (FC). Mean maximum daily air temperatures and mean daily reference evapotranspiration (grass) for the 2009 (28.2°C, 6.5 mm d-1) and 2010 (28.6°C, 6.4 mm d-1) growing seasons were similar; in 2011, these parameters were considerable greater (32.6°C and 8.8 mm d-1, respectively). For both hybrids, dry grain yields were greatest in 2009 in the I80% treatment at 9.80 and 8.04 Mg ha-1 for the LM and EM hybrids, respectively. For irrigation treatment amounts of 80% replenishment of soil water to FC, grain yields in the LM hybrid were always greater compared with the EM hybrid. However, WUE in the EM hybrid in 2009 and 2011 was 27% and 29% greater, respectively, than in the LM hybrid. Grain yield responses in both hybrids were most sensitive to the exceptional drought year of 2011 where irrigation applied at less than 80% replenishment of soil water to FC greatly reduced grain yields. Irrigation applied at less than 55% replenishment produced minimal to no grain yields.

Winter wheat agronomic traits and nitrate leaching under variable nitrogen fertilization

In the long-term field trial on an arable dystric Stagnosols, winter wheat (Triticum aestivum L.) grain yield, nitrogen use efficiency (NUE) and nitrate nitrogen (NO<sub>3</sub><sup>–</sup>-N) in lysimeter water were compared under treatments of 0, 100, 150, 200, 250 and 300 kg/ha of mineral nitrogen (N) during the growth years 1996/97, 1999/00, 2002/03 and 2005/06. Year properties significantly influenced N availability resulting in different responses of grain yield and NUE under variable treatments. Grain yield showed strong significant correlation with the rainfall accumulated from March to May (r = 0.77). In the case of a dry year 2003, winter wheat yield and NUE were adversely influenced by unfavourable climatic conditions. The optimal response of yield and NUE to increasing mineral N rates was found at the amount of 150–200 kg N/ha. Very strong significant correlation between the total amount of leached NO<sub>3</sub><sup>–</sup>-N and NUE was found for periods 1999/00 and 2005/06 where, in terms of increasing N levels, lower NUE conditioned higher NO<sub>3</sub><sup>–</sup>-N leaching (r = 0.91 and r = 0.94, respectively). According to the shallow depth of groundwater and installation of drainage systems, there is still a risk of freshwater contamination by nitrates if the N rates higher than 200 kg/ha were applied.

Climatic responses of biomass production and grain yield in Japanese high-yielding rice cultivars under different transplanting times

Planting time is one of the management methods determining yield potential in rice. The aims of the present study were to determine whether early transplanting improves yield potential in temperate regions of Japan, and to identify quantitative influences of climatic factors on crop productivity. We evaluated differences in biomass production and yield formation under three transplanting times for high-yielding cultivars having different heading characteristics. Early transplanting extended growth duration, but did not increase biomass production before heading, resulting in no improvement in total spikelet number and yield potential. For all the cultivars, cumulative air temperature better explained differences in biomass production under different transplanting times than did cumulative solar radiation. The results indicate that early-transplanted plants could not effectively utilize solar radiation for CO2 assimilation and that early biomass production in early-transplanted plants was constrained by low temperature. On the other hand, biomass production after heading and grain filling in late-heading cultivars were reduced with late transplanting time, owing to lower solar radiation and lower temperature. These results suggest that avoiding late transplanting can increase final biomass as well as acquire stable and high grain yield in late-heading cultivars in temperate regions, even if early biomass production after transplanting is reduced by low temperature. Two indica-dominant cultivars showed the highest grain yield and biomass productivity in the present study, but showed higher base temperature for biomass production, indicating that inidica-dominant cultivars were susceptible to low temperature. Development of a management method and genetic modification to promote early biomass productivity at low temperatures is necessary for further improvement of yield potential of high-yielding cultivars in temperate regions.

Winter Wheat Starter Nitrogen Management: A Preplant Soil Nitrate Test and Site-Specific Nitrogen Loss Potential

Managing highly variable soil residual nitrate-nitrogen (NO 3 –N) following corn (Zea mays L.) is difficult because it can supply starter N for winter wheat (Triticum aestivum L.) and/or be leached into water resources during the fall–winter water-recharge season in the humid eastern United States. A series of 65 starter N response studies were conducted in the Coastal Plain and Piedmont regions of Maryland to estimate the soil NO 3 –N concentration that was both agronomically sufficient and cost effective for wheat. A subset of studies measured soil NO 3 –N loss (0–60 cm) during the fall–winter season, and additional studies evaluated bromide (Br) to index potential NO 3 –N leaching. A soil exchange frequency index [EFI = rainfall * (available soil water capacity) −1 ] was used to identify where NO 3 –N loss was high and wheat response to starter N was unlikely. A post-planting fall EFI ³ 2.5 was associated with NO 3 –N depletion of >65% (0–60 cm). A significant (P < 0.001) linear-plateau relationship was found between preplant soil NO 3 –N concentration (0–30 cm) and wheat grain-yield response to starter N for locations with EFI < 2.5. This agronomic linear-plateau relation was combined with a break-even economic scenario (fertilizer-N cost = grainresponse value) to estimate the fall NO 3 –N sufficiency for wheat, which was 7 mg NO 3 –N kg −1 soil (0–30 cm) and corresponded to 9 mg NO 3 –N kg −1 soil (0–15 cm). These findings show that a preplant soil NO 3 –N test for winter wheat can facilitate identification of sites where starter N will produce economic returns and reduce potential NO 3 –N losses to water resources. Abbreviations: AWHC, available water holding capacity between FC and PWP; Br, bromide; CV, coefficient of variation; EFI, exchange frequency index; FC, soil water content at field capacity; GS, growth stage; IC, ion-chromatography; LPNR, location previous N regimes; NDFF, the percent of plant N derived from fertilizer; NO 3 –N, nitrate-nitrogen; PWP, soil water content at permanent wilting point; UAN, urea-ammonium nitrate; URS, university research stations.

Second‐Year Corn after Alfalfa Often Requires No Fertilizer Nitrogen

Terminated alfalfa(Medicago sativaL.) often provides N to at least 2 yr of subsequent corn (Zea maysL.) crops, but the variability in fertilizer N guidelines for second‐year corn in the midwestern United States needs to be addressed. In several states, fertilizer N guidelines are the same for second‐year corn after alfalfa as they are for continuous corn, whereas other states recommend reducing fertilizer N rates to second‐year corn by 25 to 145 kg N ha−1. Experiments were conducted at 28 farms in Iowa and Minnesota to determine fertilizer N requirements of second‐year corn after alfalfa. Second‐year corn in half of the trials showed no response to fertilizer N and the economically optimum N rate (EONR) for corn grain yield in the 14 responsive trials ranged from ≤67 to 196 kg N ha−1. Furthermore, in 10 of 19 trials there was no response of grain yield to fertilizer N in both first‐ and second‐year corn. These results indicate that current university fertilizer N guidelines for second‐year corn after alfalfa often are unreliable. At the widely adopted critical concentration of 21 mg kg−1, the pre‐sidedress soil nitrate test (PSNT) correctly identified only 63% of the trials as responsive or nonresponsive to fertilizer N. When results of our experiments were combined with data from the literature, second‐year corn grain yield responded to fertilizer N 55% of the time and the PSNT remained accurate only 65% of the time, indicating that more accurate forecasting of second‐year corn N requirements is needed.

Grain yield and phosphorus use efficiency of wheat and pea in a high yielding environment

The aim of the present study was to evaluate the response of grain yield, phosphorus (P) use efficiency (PUE, g yield g –1 P available) and related root traits of wheat and pea to different P availabilities in a high yielding environment (e.g.: yield higher than 10 Mg ha -1 for wheat). Two experiments were conducted in southern Chile. Treatments consisted of the combination of (i) two crops (spring-bred wheat and pea) and (ii) three rates of P fertilization (0 (P0), 100 (P1) and 250 (P2) kg P ha –1 ). Grain yield of wheat was more sensitive to P deficiency than pea. Wheat showed consistently higher (P < 0.01) PUE than pea, averaging 195 and 125 g yield g –1 P available, respectively. This was principally ascribed to the highest (P < 0.01) P utilization efficiency of wheat (430 vs. 249 g yield g –1 P uptake for wheat and pea, respectively). On the contrary, the P uptake efficiency was slightly different for these crops (0.44 and 0.49 g P g –1 P available, respectively). However, these crops presented different strategies for P acquisition. Wheat had a higher (P < 0.01) soil exploratory capacity than pea, while pea showed a higher (P < 0.01) P uptake per unit of root length than wheat. Wheat showed higher PUE than pea; however, crop differences are ascribed to differences in phosphorus utilization rather than to phosphorus uptake efficiency. This information could contribute to optimized soil P use and improved crop fertilization management.

The response of durum wheat to the preceding crop in a Mediterranean environment.

Crop sequence is an important management practice that may affect durum wheat (Triticum durum Desf.) production. Field research was conducted in 2007-2008 and 2008-2009 seasons in a rain-fed cold Mediterranean environment to examine the impact of the preceding crops alfalfa (Medicago sativa L.), maize (Zea mays L.), sunflower (Helianthus annuus L.), and bread wheat (Triticum aestivum L.) on yield and N uptake of four durum wheat varieties. The response of grain yield of durum wheat to the preceding crop was high in 2007-2008 and was absent in the 2008-2009 season, because of the heavy rainfall that negatively impacted establishment, vegetative growth, and grain yield of durum wheat due to waterlogging. In the first season, durum wheat grain yield was highest following alfalfa, and was 33% lower following wheat. The yield increase of durum wheat following alfalfa was mainly due to an increased number of spikes per unit area and number of kernels per spike, while the yield decrease following wheat was mainly due to a reduction of spike number per unit area. Variety growth habit and performance did not affect the response to preceding crop and varieties ranked in the order Levante > Saragolla = Svevo > Normanno.

Response of Grain Yield and Protein Content of Wheat Varieties to Different Levels of Fertilizers

The grain yield and protein content of winter and spring wheat are significantly influenced by the technological factors, by variety, meteorological conditions and interaction between them. The field experiment was conducted to evaluate the effect of different levels of fertilization on grain yield and quality indices in winter and spring wheat and to compare of their values. The quality of the grain was determined based on meal analysis. Nitrogen application improved protein content and also increase the grain yield until level when is appear the negative correlation between two characters. The experimental date from this paper is about adaptability of 25 winter wheat and 22 spring wheat varieties local and foreign in two years and two level of fertilization on the local conditions at Turda. The experiments were conducted over two years, 2011 and 2012, at Agricultural Research and Development Station Turda, which are characterized with a high rainfall and temperatures favourable for winter wheat and spring wheat crops. The trials were conducted under quadratic lattice design with repeated the basic scheme. Each of both basic scheme consisting of 3 replications permitted to create two levels of fertilization. So, including the years as factors was possible to consider our experiment as an three factorial one (years- cultivars- fertilization). The effect of fertilization is reflected on increase grain yield and qualitative of these. By analysis of variance could be highlighted the influences of year, level of fertilization and cultivars, and also the interactions between these.

Responses of rice production, milled rice quality and soil properties to various nitrogen inputs and rice straw incorporation under continuous plastic film mulching cultivation

Yield decline from continuous cropping of aerobic rice is a constraint to the widespread adoption of plastic film mulching cultivation (PFMC); rice straw incorporation has been proposed to counter this negative effect of long term PFMC. Shifts in water management from flooded to aerobic conditions are known to influence the availability of N and might have an influence on rice quality. A long-term (2001–2010) field experiment was conducted to examine the effects of five fertilizer nitrogen (N) application rates (0, 45, 90, 135, 180kgNha−1) and rice straw incorporation on rice grain yield, milled rice quality and soil quality under PFMC in non-flooded conditions. There were significant responses in grain yield to various N fertilizer rates and rice straw incorporation during 2008 to 2010. Total amino acids and protein concentrations in polished rice increased with increasing N rates. Split-plot factor significantly affected soil fertility and rice plant N uptake in our study. With rice straw incorporation, total annual and mean amount of soil organic matter was improved by 6.4%, 7.6% and 12.2%; NH4OAC-extractable K amount was improved by 28.2%, 64.0% and 52.9%; N uptake was improved by 20.4%, 23.9% and 23.6%, respectively, from the year of 2008 to 2010. Dynamics of rice grain yield, soil organic matter, alkali-hydrolyzable N and NH4OAC-extractable K from 2001 to 2010 proved that rice straw incorporation obviously improved rice grain yield and soil quality under continuous PFMC. Our results suggest that there is a possibility of reversing yield decline observed in the continuous PFMC system by using rice straw incorporation.

Grain yield and nitrogen use efficiency responses to N application in Bt (Cry1Ab/Ac) transgenic two-line hybrid rice

Transgenic crops with Bacillus thuringiensis (Bt) have been reported to be effective in controlling pests, and some Bt transgenic lines have been used to develop hybrid crop varieties including three-line and two-line hybrid rice (THR). However, it is unclear whether the insertion of an external Bt gene affects nitrogen uptake and N use efficiency (NUE) along with the grain yield of Bt-THR. Thus, field experiments were conducted in two adjacent fields located at Zhangbang village, Hubei province, China from May to October in 2011 and 2012. Treatments were arranged using a split-plot design with four replications. The main plots were N treatments with three rates (90, 135, 180kgha−1) in 2011 and four rates (0, 90, 135, 180kgha−1) in 2012. Four different tested varieties were grown in the subplots. The three Bt-THR examined were Guangliangyou-19 (GLY-19), Chuanyou-4198 (CY-4198), and Zheyou-3 (ZY-3), and the non-Bt control was Yangliangyou-6 (YLY-6) which was used as the check for the national variety traits in China at present. Pests (including Bt target pests, diseases and weeds) were strictly controlled to avoid yield loss. No significant differences were observed in the grain yield between GLY-19, ZY-3 and YLY-6 at each N application for both years. However, the grain yield in response to different N rates varied among different Bt-THR varieties and the control. CY-4198 showed a sensitive N response trait, which produced a maximum grain yield at 90kgNha−1, and further increases in N rates caused a yield decline. The other Bt-THR varieties demonstrated insensitive N responses similar to the control, where the maximum grain yield was at 135kgNha−1 and showed no significant yield decline when applied at 180kgNha−1 in both years. Among the three Bt-THR varieties, GYL-19 and ZY-3 demonstrated a similar N uptake ability, agronomic nitrogen use efficiency, N harvest index, N translocation efficiency, and recovery efficiency compared to the control, whereas those for CY-4198 was lower when the N application exceeded 90kgNha−1. In conclusion, some Bt-THR varieties (GLY-19 and ZY-3) demonstrated a comparable yield potential to the super hybrid control (YLY-6). Moreover, there was no evidence that insertion of the Bt gene changed N uptake and NUE-related traits, which indicated that the optimal N managements adapted by the THR varieties could also be introduced to Bt-THR. Thus, screening Bt-THR varieties might represent a feasible approach to synergistically improve grain yield and pest resistance without disrupting N nutrition.

Testing the suitability of the end-of-season stalk nitrate test for summer corn (Zea mays L.) production in China

The end-of-season corn stalk nitrate test (CSNT) is a desirable indicator of N status and functions as a guide for agricultural practice and regulation of corn production. Our objectives were to evaluate the CSNT concentration of three summer corn varieties: XY335, introduced from the US; YD13, a senescent hybrid; and ZD958, a “stay-green” hybrid, under different N application rates and to validate the feasibility of using the CSNT criteria developed in the US for summer corn production in China. The response of grain yield and N uptake to N availability fit a linear-plateau model, whereas the CSNT concentration of summer corn increased linearly with increasing N availability, indicating excess N accumulated in the stalk as nitrate when luxury N consumption occurred. The CSNT concentrations among the different varieties increased in the order XY335<YD13<ZD958. The United States CSNT category range (0.70–2.0gkg−1) was suitable only for XY335, which was introduced to China from the US. For ZD958 and YD13, the optimal CSNT categories to achieve maximum grain yield were 0.9–5.36gkg−1 and 0.56–4.56gkg−1, respectively. The study results suggest that it is not necessary to adjust the US CSNT criteria for different geographical regions, but new categories may be needed for varieties that are not used in the US.

Response of Grain Yield to Plant Density and Nitrogen Application Rate for Maize Hybrids Released from Different Eras in Heilongjiang Province

Response of Grain Yield to Plant Density and Nitrogen Application Rate for Maize Hybrids Released from Different Eras in Heilongjiang Province

Response of Nitrogen Use Efficiency to Plant Density and Nitrogen Application Rate for Maize Hybrids from Different Eras in Heilongjiang Province

In this study, eight typical maize hybrids released from 1970s to 2000s in Heilongjiang Province were selected to investigate the responses of grain yield, nitrogen (N) partial factor productivity (PFP), N agronomic efficiency (NAE) and N recovery efficiency (NRE) to N application rate and plant density in 2009 and 2010. During the variety improvement period of 1970s–2000s, PFP and NRE increased significantly by 3.41 kg kg–110 yr–1and 2.26 percent 10 yr–1, respectively. NAE increased significantly from 1970 to 1990 and descended after 1990. N harvest index decreased significantly by 1.51 per cent 10 yr–1. Grain N, stem N and leaf N accumulations rose significantly by 0.09, 0.07, and 0.12 g plant–110 yr–1. There were significant interactions among eras, plant densities and N application rates for above indicators. Nitrogen use efficiency exhibited decline trends with increasing N application rate and parabolic shape response to increasing plant density, and got the maximum in the population range of 50 000–70 000 plants ha–1. The theoretical optimal plant density for the maximal NUE was higher in newer hybrids than in the older ones. Higher plant population led to decrease N accumulation and N harvest index in grain, stem and leaf for all hybrids from different eras. Higher N application rate tended to promote N accumulation in grain, stem and leaf, but had different effects on N harvest index for hybrids from different eras. Compared to the varieties released abroad, there is a great potential in maize variety improvement for high-yield and high-NUE in Northeast China. According to the existing variety’s traits, increasing plant density can enhance not only maize yield but also NUE.

Zinc bioavailability response curvature in wheat grains under incremental zinc applications

Zinc application is generally recommended to enrich wheat grains with Zn; however, its influence on Zn bioavailability to humans has not received appreciable attention from scientists. In this pot experiment, seven Zn rates (from 0 to 18 mg kg−1 soil) were applied to two wheat cultivars (Shafaq-2006 and Auqab-2000). Application of Zn significantly increased grain yield, grain Zn concentration and estimated Zn bioavailability, and significantly decreased grain phytate concentration and [phytate]:[Zn] ratio in wheat grains. The response of grain yield to Zn application was quadratic, whereas maximum grain yield was estimated to be achieved at 10.8 mg Zn kg−1 soil for Shafaq-2006 and 7.4 mg Zn kg−1 soil for Auqab-2000. These estimated Zn rates were suitable for increasing grain Zn concentration and Zn bioavailability (>2.9 mg Zn in 300 g grains) to optimum levels required for better human nutrition. Conclusively, Zn fertilization for Zn biofortification may be practiced on the bases of response curve studies aimed at maximizing grain yield and optimum Zn bioavailability. Moreover, additive Zn application progressively reduced the grain Fe concentration and increased the grain [phytate]:[Fe] ratio. However, a medium Zn application rate increased grain Ca concentration and decreased the grain [phytate]:[Ca] ratio. Hence, rate of Zn application for mineral biofortification needs to be carefully selected.

Changes in Nitrogen Use Traits Associated with Genetic Improvement for Grain Yield of Maize Hybrids Released in Different Decades

ABSTRACTFurther enhancement of maize (Zea mays L.) N‐use efficiency (NUE) will benefit from a thorough understanding of how genetic improvement has shaped N use parameters. Since selection for grain yield has occurred at high N fertilizer rates, our hypothesis was that modern hybrids would have a greater response to supplemental N than hybrids from earlier eras. In 2009 and 2010, 21 single‐cross maize hybrids released between 1967 and 2006 were characterized for grain yield and N use traits. While the ability to acquire mineralized soil N did not change over era, the utilization increased with decade of introduction (0.24 kg kg–1 of plant N [kgplantN–1] yr–1; R2 = 0.37). Increases of grain yield at high N (86 kg ha–1 yr–1; R2 = 0.68) over era were accompanied by increases at low N of 56 kg ha–1 yr–1 (R2 = 0.69). Grain yield improvements at all levels of N were associated with decreased barrenness and increased kernel number expressed on a per‐plant and per‐area basis. Fertilizer N response, NUE, increased at a rate of 0.16 kg kg–1 of fertilizer N (kgN–1) yr–1 (R2 = 0.40). Increased NUE was positively correlated with improved N‐uptake efficiency (r = 0.76, P ≤ 0.001), due to the greater postflowering N uptake of more recent hybrids. The response of grain yield to fertilizer N in current hybrids is more dependent on uptake of fertilizer N than the efficiency of fertilizer N utilization, and approximately two‐thirds of genetic gain for grain yield at high N can be explained by improvements in grain yield at low N.

Responses of photosynthesis, chlorophyll fluorescence, and grain yield of maize to controlled‐release urea and irrigation after anthesis

AbstractControlled‐release urea (CRU) is a new type of urea, which may increase crop nitrogen (N)‐use efficiency compared with conventional urea (CU), but the conditions where it outperforms urea are not well defined. A field experiment assessing responses of plant growth and grain yield of maize to CRU and irrigation was conducted on a typical agricultural farm in Shandong, China. Five treatments of the two types of urea (75, 150 kg N ha–1, 0 kg N ha–1) were applied as basal fertilizer when sowing maize, and two water treatments (W0 and W1) were used 23 d after anthesis. Net photosynthetic rate (PN) and chlorophyll concentration as well as leaf‐area index (LAI) increased significantly by both CRU and CU application, with the increases being larger in CRU‐treated plants than in CU‐treated plants at grain filling and maturing stages. CRU significantly enhanced the maximum photochemical efficiency (Fv / Fm), PSII coefficient of photochemical fluorescence quenching (qP), and actual quantum yield of PSII electron transformation (ΦPSII) but decreased the nonphotochemical quenching (NPQ). Cob‐leaf N concentration of CRU‐treated plants was significantly higher than that of CU‐treated plants under no irrigation, but not in the irrigation treatment 30 d after anthesis. Significant positive correlations were found between cob‐leaf N concentration and PN both with and without irrigation. Grain yield of maize was significantly higher in the CRU treatment than in the CU treatment under both irrigation conditions. In conclusion, CRU as a basal application appeared to increase the N‐use efficiency for maize relative to CU especially by maintaining N supply after anthesis.

Root-lesion nematode (Pratylenchus thornei) reduces nutrient response, biomass and yield of wheat in sorghum–fallow–wheat cropping systems in a subtropical environment

Wheat in winter and grain sorghum in summer are the most important crops of the subtropical grain region of eastern Australia, where they are often grown in sequences of 1–4 years of each crop species separated by a long fallow period of 11–14 months. Growers have observed that the second wheat crop in sequence can appear nutrient deficient with poor growth and grain yield compared with the first or subsequent crops. To investigate this problem, wheat was grown in various field experiments as the first–fourth wheat in sequence after long fallow from sorghum sequences of various lengths (one–four years) to test for responses in biomass production and grain yield to fertilisers, biocidal fumigants and nematicides. Populations of root-lesion nematodes (Pratylenchus thornei) were greatest in the soil before the second wheat crop was sown than before the first or third wheat crops. Greatest responses in wheat growth were obtained to the nematicide aldicarb in various wheat sequence positions up to the fourth (up to 137% increased yield of second wheat). Aldicarb best protected the roots from P. thornei allowing increased nutrient response. The fumigants chloropicrin and dazomet caused substantial changes in soil microbial populations and available nutrients, but the systemic nematicides fenamiphos and aldicarb did not. Responses in grain yield were also obtained to N fertiliser and less frequently to P and Zn (41% increase of second wheat to NPZn fertiliser), with best overall responses to a combination of aldicarb and fertiliser. A range of tolerance to P. thornei, as judged by both grain yield from nil treatment and response to aldicarb and/or fertiliser, was identified among wheat cultivars. In comparison, one barley cultivar yielded maximally without treatment (up to 3.7 and 1.3 times the yield of the most intolerant and the most tolerant wheat cultivars, respectively). Integrated management using crop rotation with sorghum to reduce P. thornei populations combined with growing tolerant wheat and barley cultivars supplied with adequate fertiliser are practical measures to reduce the impact of P. thornei.

Rainfall as a Limiting Factor for Wheat Grain Yield in Permanent Raised‐Beds

The planting system on permanent raised‐beds for rainfed wheat (Triticum aestivum L.) production in the central highlands of Mexico is an option that needs to be documented for moderate‐yield environments. Long‐term plots were established under this technology in the 2002 crop season. The objective was to evaluate wheat grain yield performance as related to rainfall and soil characteristics until 2009. The experiment was conducted in rotation with maize (Zea mays L.) and monoculture. Four N rates were applied to wheat (0, 40, 80, and 120 kg ha−1) and three to maize (0, 60, and 120 kg ha−1). Nitrogen rates to the subsequent wheat crop were superimposed to each one of the preceding maize crop. Crop residues of both crops were left on the soil surface. Results showed that the amount of soil N measured as N–NO3 and N–NH4 was reduced during the first three seasons after the establishment of permanent beds. Although this reduction was substantial, stepwise regression procedures indicated that wheat grain yield was mostly determined by the amount of rainfall and distribution during the crop season, except for the 2009 season when the standard deviation of this measurement was larger. In addition to those N measurements, total soil N, available P, and exchangeable K had no effect on grain yield. The response of grain yield to N application rates &gt;40 kg ha−1 was negligible for both crop rotations. In average, wheat grain yield in rotation was greater than wheat in monoculture. Grain yield reduction in monoculture resulted from fewer heads m−2.