Difference In Wheat Yield Research Articles

Combined Application of Chemical and Organic Fertilizers: Effects on Yield and Soil Nutrients in Spring Wheat under Drip Irrigation

In this study, we established a feasible fertilization programming method for wheat production by exploring the effects of the combined application of chemical and organic fertilizers on wheat yield, nutrient uptake, soil nutrient content, and fertilizer utilization. Six treatments, no fertilizer (CK), conventional fertilizer (CF), optimized fertilizer (with reduced fertilizer amount) (RF), chemical fertilizer with organic fertilizer extract (RPAE), partial replacement of chemical fertilizer with raw amino acid powder (RAF), and partial replacement of chemical fertilizer with raw humic acid powder (RHF), were set up for a field experiment. The fertilizer application rates for the RF treatment were calculated based on fertilization-monitoring techniques (30.3% nitrogen and 24.8% phosphorus reductions in 2022 and 23.0% nitrogen and 1.5% phosphorus reductions in 2023). The effects of different fertilizer treatments on yield, dry matter accumulation, plant nutrient accumulation, soil nutrients, and nutrient utilization in wheat were investigated. The results showed that, on the basis of 23% nitrogen and 1.5% phosphorus reductions, there was no significant difference in wheat yield between the RF and CF treatments and that the utilization rate of nitrogen fertilizer was improved. The application of organic fertilizer promoted dry matter accumulation in different organs of wheat; increased plant nutrient accumulation; improved soil nutrient content, nutrient utilization rate, nutrient partial productivity, and nutrient agronomic use efficiency; and ensured stable and increased crop yield. Specifically, compared with CF, the RPAE, RAF, and RHF organic fertilizer treatments increased wheat yield by 3.85%, 1.97%, and 0.67%, respectively, and the utilization of nitrogen and phosphorus fertilizers induced by these treatments significantly increased by 40.46%, 39.28%, and 37.46% (nitrogen) and by 9.83%, 8.91%, and 7.46% (phosphorus), respectively. As a result of our experiment, we concluded that RPAE exerted the best effects among the three organic fertilizer treatments (RPAE, RAF, and RHF) and that its use can result in a higher wheat yield and fertilizer utilization rate in drip-irrigated wheat fields. The results of this study provide a theoretical basis for the combined application of chemical and organic fertilizers, which is conducive to sustainable agriculture development.

Optimizing agronomic practices for hard winter wheat production in the Great Plains with respect to seeding rate, row spacing, and variety

AbstractWinter wheat (Triticum aestivum L.) yield in dryland areas is optimized by the improvement of genetics in combination with ideal production practices. Different combinations of seeding rate and row spacing can influence the development of wheat plants, impacting wheat yield and its components. To determine the influence of these practices, yield components, water use efficiency (WUE), biomass, and subsequent grain yield were evaluated in an experiment conducted at the High Plains Agricultural Laboratory, Sidney, NE, from 2019 until 2022, using a split‐plot randomized complete block design with four replications. Treatments consisted of four different row spacings (19, 25, 31, and 51 cm), three seeding rates (1.05, 2.1, and 3.1 million seeds ha−1), and two high performing winter wheat varieties—‘Ruth’ and ‘Robidoux’. Row spacing showed differences in wheat yield (p < 0.0001) across all years, with a significant effect of seeding rate only in 1 year and an interaction effect of the three factors in 2022 alone. Higher wheat yield was achieved with the two narrower row spacings (19 and 25 cm) compared to the wider row spacings of 38 and 51 cm. The treatment combining the 19 cm row spacing and either 2.1 or 3.1 million seed ha−1 seeding rate had the greatest yields in most years. Narrower row spacings had improved WUE in drier years as compared to wider row spacings.

Long‐term yield response of corn, wheat, and double‐crop soybean to tillage and N placement

AbstractOn claypan soils of the eastern Great Plains, yield of no‐till crops often lags yield of crops grown with tillage, especially cereals requiring sound N management. The objective of this 14‐yr study was to determine the yield response of corn (Zea mays L.), winter wheat (Triticum aestivum L.), and double‐crop soybean [Glycine max (L.) Merr.] in a 2‐yr rotation to tillage system and N fertilizer placement. Tillage, N placement, or their interaction affected corn yield in all seven‐corn crop‐years. Corn yields averaged about 25% lower with no‐till than with conventional or reduced tillage and were never greater with no‐till in any year. Nitrogen fertilization increased corn yield by increasing kernels per ear; however, corn yield increase to subsurface band (knife) N applications compared with surface (broadcast or dribble) applications was only about 10%. In the lower‐yielding no‐till system, corn yield increase to knifed N fertilization was greater than in tilled systems and may partially ameliorate the no‐till yield decline. Average wheat yield was unaffected by tillage. Adding N more than doubled wheat yield, but differences in wheat yield between preplant N placements methods were small. Average double‐crop soybean yield was unaffected by tillage with few, inconsistent differences by year. Compared with no‐till, tillage tended to increase soil P and K, but soil organic matter was just redistributed with no net increase with no‐till. Thus, tillage and N placement treatments may affect corn but have lesser effects on wheat and double‐crop soybean and soil properties in this rotation.

Plastic film mulching increases yield, water productivity, and net income of rain-fed winter wheat compared with no mulching in semiarid Northwest China

Whole-ground plastic film mulching with thin soil mulching above the film (PMS) and no mulching (NM) are the two dominant planting patterns for winter wheat in the semiarid rain-fed region (mean annual precipitation <450 mm) of Northwest China. In this study, differences in water consumption and production performance between PMS and NM were analyzed, as well as reasons for differences in wheat yield, in 24 field experiments conducted from 2008 to 2019 at three sites. Compared with NM, PMS had higher average grain yield (23.2%), crop water productivity based on grain yield (25.6%), and net income (603 ¥ ha−1) across all 24 experiments. In PMS, yield stability also improved under different environments. Yield differences between planting patterns and among environments primarily depended on differences in spike number ha−1. Average consumption of pre-sowing stored water in soil from 0 to 200 cm in PMS and NM accounted for 38% and 35%, respectively, of total evapotranspiration (ET). In early (sowing–jointing), middle (jointing–flowering), and late (flowering–maturity) phases, average water consumption in PMS was 36.4%, 39.3%, and 24.3%, respectively. In the middle phase, PMS increased water consumption by 29 mm and the proportion of water consumption relative to total ET by 5.6% compared with NM. In early and late phases, water consumption was similar in PMS and NM. Increased water consumption in the middle phase could increase vegetative growth and sink capacity (grain yield ha−1). ET, yield, and vegetative growth were highly positively correlated with one another. Compared with NM, PMS significantly increased yield and crop water productivity by maximizing transpiration, increasing water consumption in the middle phase, and improving use of pre-sowing stored water. In conclusion, PMS is suitable to cultivate wheat for improving water productivity and economic benefits in the semiarid rain-fed agricultural region of Northwest China.

Long‐term reduced tillage and no‐till cropping systems affect crop yields and economics

AbstractThere has been increased implementation of conservation practices on highly erodible Missouri soils. The objectives were to evaluate the effects of long‐term no‐till and reduced tillage cropping systems on yields and economics of production systems. Research was initiated in 1994 near Novelty, MO. Treatments included a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.]–wheat (Triticum aestivum L.) rotation with three tillage/cropping systems: (1) no‐till corn–soybean–wheat with double‐crop soybean (NT DCS), (2) no‐till corn–soybean–wheat with frost‐seeded red clover (Trifolium pratense L.) cover crop (NT FSC), and (3) reduced‐till corn–soybean–wheat (RT). Each crop and cropping system was represented each year in large plots (9.1 by 90 m). Significant differences in corn yields occurred in 1995–1996, 2000, 2009–2010, and 2015–2016 with the highest‐yielding treatments being five RT, one NT DCS, and one RT = NT DCS. Significant differences in soybean yield occurred in 3 yr with the highest‐yielding cropping system being NT DCS twice and RT once. Significant differences in wheat yield occurred in 4 yr with RT yielding the highest each time. Input costs were greatest in RT and NT DCS, while net income was greatest in NT DCS, which produces four cash crops in 3 yr. Highest net returns occurred in NT DCS, which was US$135 and 145 ha–1 greater than NT FSC and RT, respectively. The productivity and economics of systems need to be balanced with ecosystem benefits of NT. In this corn–soybean–wheat rotation, hybrid cropping systems including RT corn and wheat, followed by NT DCS, and NT soybean is recommended.

Wheat yield as a measure of the residual fertility after 20 years of forage cropping systems with different manure management in Northern Italy

After 20 years of application of different manure types, cropping systems and additional nitrogen (N) levels, their residual fertility effects were compared by measuring the yield of a following unfertilised wheat crop (Experiment 1), which was sown on exactly the same plots of the previous long-term trial. All previously applied factors caused significant differences in wheat yield. Wheat yielded more on plots that had received farmyard manure (FMY) compared to those where semi-liquid manure (SLM) was previously applied. Long-term application of a semi-intensive rotation, with three years of annual double cropping of autumnsown Italian ryegrass and spring-sown silage maize followed by three years of mown lucerne (R6), resulted in higher wheat yield than application of just the annual double cropping of Italian ryegrass and silage maize (R1). Application of further mineral N fertilisation to previous cropping systems caused higher yield of the subsequent wheat crop. The difference in wheat yield between the R6 and R1 systems was greater with SLM (+28%) than FYM application (+11%) resulting in a significant manure × system interaction. A companion experiment (Experiment 2) was carried out to compute the nitrogen agronomic efficiency (NAE) from the yield of wheat plots that were sown after ploughing a nearby 20- year unfertilised grassland and received four levels of mineral N fertilisation. NAE was further used to empirically estimate the productive advantage (PA) conferred by previous manure-systemmineral nitrogen combinations in the long-term trial. PA was measured as equivalent kg of mineral N to be applied to wheat to achieve the yield level recorded after any previous combination. The estimated PA values were much higher when wheat followed FYM compared to SLM application, and when it followed R6 compared to R1 system. The SLM-R1 combination had negative PA values, indicating a productive disadvantage on wheat of this preceding combination. The enhancement of residual soil fertility by long-term application of FYM compared to SLM could be attributed to greater nutrient provision during the years by FYM than by SLM. However, further fertility advantages of FYM are discussed. Despite lower nutrient supply by organic fertilisers in R6 than in R1 system, the former had higher residual fertility. The presence of lucerne in the R6 rotation likely enriched the soil in nitrogen and increased its availability for following cropping. Possible benefits of the legume on the soil suppressiveness might have been a further asset of the R6 system.

Can Cover or Forage Crops Replace Fallow in the Semiarid Central Great Plains?

Growing a crop in place of fallow may improve soil properties but result in reduced soil water and crop yields in semiarid regions. This study assessed the effect of replacing fallow in no‐till winter wheat (Triticum aestivum L.)–fallow with cover, forage, or grain crops on plant available water (PAW), wheat yield, grain quality, and profitability over 5 yr, from 2007 to 2012. Plant available water at wheat planting was reduced the most when the fallow period was the shortest (i.e., following grain crops) or when biomass production was the greatest. Winter and spring lentil (Lens culinaris Medik.) produced the least biomass, used the least soil water, and had the least negative effect on yield. For every 125 kg ha−1 of cover or forage biomass grown, PAW was reduced by 1 mm, and for every millimeter of PAW, wheat yield was increased by 5.5 kg ha−1. There was no difference in wheat yield whether the preceding crop was harvested for forage or left as standing cover. In years with above‐average precipitation, wheat yield was reduced 0 to 34% by growing a crop in place of fallow. However, in years with below‐average precipitation, wheat yield was reduced 40 to 70% without fallow. There was minimal negative impact on wheat yield growing a cover or forage crop in place of fallow if wheat yield potential was 3500 kg ha−1 or greater. Net returns were reduced 50 to 100% by growing a cover crop. However, net returns were increased 26 to 240% by growing a forage crop. Integrating annual forages into the fallow period in semiarid regions has the greatest potential for adoption.

Assessment of Double‐Crop and Relay‐Intercropping Systems of Peanut with Soft Red Winter Wheat and Residual Herbicides

Core Ideas The southern United States has long warm seasons where relay‐intercropping could have benefits. Wheat followed by peanut can be a successful cropping system if managed correctly. Herbicide strategies are important when considering relay‐intercropping systems. Double‐cropping peanut after wheat was more successful than relay‐intercropping. Neither imazapic nor pyroxasulfone caused injury to peanut or Clearfield wheat. Multiple‐cropping systems for peanut (Arachis hypogaea L.) have potential in the southeastern United States where a prolonged growing season exists. Full‐season soft red winter wheat (Triticum aestivum L.) production typically pushes peanut planting later than optimum, but a relay‐intercrop (RI) system may allow peanut to be planted on‐time while still harvesting wheat grain. However, practical approaches for weed control in this system must be identified. Project objectives were to determine the most effective cropping systems to maximize wheat and peanut potential and assess efficacy and injury to wheat and peanut following different herbicide programs. Twelve cropping systems included variations of double‐crop (DC), RI, and monocrop (MC) management. Studies were conducted at Tifton and Plains, GA, in 2011 and 2012. The RI treatments averaged 20 to 42% less wheat yield than DC systems. Similarly, peanut yield averaged 20 to 26% less, total sound mature kernels (TSMK) (2–7%) were reduced, and more tomato spotted wilt virus (TSWV) (Tospovirus) incidence (4–5%) occurred with earlier planting (RI and traditional MC scenarios) compared with later planting (DC and late MC). There were no differences in wheat yield when sprayed with imazapic compared with nonsprayed, indicating imazapic is not an injury concern in imidazolinone‐resistant wheat. Growers interested in producing peanuts and wheat in the same year would be at an advantage to use a DC system, and have several herbicide options without major risk of injury to wheat or peanut.

Atributos químicos do solo associados à produtividade do trigo em um talhão com diferentes potenciais produtivos

Potenciais produtivos distintos têm sido verificados entre talhões, bem como dentro desses, em áreas sob muitos anos de plantio direto (PD). Ferramentas de agricultura de precisão (AP) podem auxiliar a identificar tais diferenças, mas para manejar eficientemente a fertilidade do solo nessas condições a amostragem deve ser representativa. Este trabalho teve como objetivo avaliar a influência de atributos químicos do solo, conforme a camada ou profundidade de amostragem, na produtividade da cultura do trigo, em uma área sob PD de longa duração, utilizando zonas de um talhão com potenciais produtivos distintos. O estudo foi feito em Reserva do Iguaçu, PR, em área com 25 anos de PD e cinco anos de adoção de técnicas de AP. A partir de mapas de colheita anteriores, identificaram-se duas zonas, Z1 (alta produtividade) e Z2 (baixa produtividade), onde se estabeleceram malhas com 16 unidades amostrais. A produtividade do trigo foi estimada em três pontos por unidade, coletando-se amostras de solo de 0,0-0,1 e de 0,1-0,2 m nos mesmos pontos. A produtividade do trigo foi 22 % maior em Z1 do que em Z2, de acordo com os mapas de colheita utilizados. Os teores de carbono orgânico do solo (Corg) foram maiores em Z1, nas duas camadas do solo. Na camada de 0,1-0,2 m, a saturação (m%) e os teores de Al3+ foram significativamente maiores em Z2; nessa camada, Z1 apresentou maiores valores de pH e saturação por bases (V%) e teores de Ca2+, Mg2+ e K+. Houve correlação positiva da produtividade com os teores de Corg nas duas camadas do solo. Considerando somente a camada de 0,1-0,2 m, a correlação foi positiva com os valores de pH e V% e com a disponibilidade de Ca2+, Mg2+ e K+; e negativa, com a disponibilidade de Al3+. As diferenças na fertilidade do solo entre Z1 e Z2 se deram principalmente na camada de 0,1-0,2 m e foram associadas à diferença de produtividade do trigo, indicando ser importante a presença desse estrato na amostragem do solo em áreas de PD de longa duração, visando representar corretamente o estado de fertilidade do solo.

The effect of white‐tailed deer browsing on wheat quality and yields in Delaware

AbstractLocally overabundant white‐tailed deer (Odocoileus virginianus; hereafter, deer) have caused increased damage to agronomic crops across their range. Winter wheat (Triticum aestivum) is grown in &gt;60% of the states in the United States where white‐tailed deer occur. Although the effect of deer browsing on corn (Zea mays) and soybean (Glycine max) yields has been documented, research on the effect of deer browsing on winter wheat yields and quality is limited. In 2007–2009, we investigated the effect of deer browse timing and wheat type (bearded and unbearded) on yields and quality in Delaware, USA. We randomly stratified 3 treatments (i.e., no protection, protected at planting, or protected prior to heading) in 1,680 plots. After head emergence, we surveyed the plots weekly to estimate browse rates and biomass removed by deer. We harvested a 1‐m2 area in the middle of each plot to determine the deer impact on yield. Browsing increased in intensity as head development progressed and more browsing occurring on the unbearded wheat. Unprotected plots had 195 kg/ha greater wheat yield than did protected plots in 2007 (P = 0.08). We found no difference in wheat yield among treatments during 2008 and 2009 (P = 0.38). Bearded wheat fields had 379 kg/ha greater wheat yield during 2007 and 399 kg/ha greater yield during 2008 and 2009 than did unbearded wheat fields (P &lt; 0.001). We also observed no difference in wheat quality among treatments or between types of wheat (P &gt; 0.417). Our browse surveys suggested avoidance of bearded wheat but the overall browsing was not intense enough to affect yield. Our results demonstrated that white‐tailed deer had no impact on wheat yield at a deer density of 15 deer/km2. © 2013 The Wildlife Society.

Winter Wheat and Red Clover Intercrop Response to Tillage and Compost Amendment

ABSTRACTFrost‐seeding red clover (Trifolium pratense L.) into winter cereals is an efficient establishment method, although performance under contrasting soil management practices remains unclear. Wheat and intercropped red clover productivity were evaluated in intensive tillage (IT), moderate tillage (MT), and no tillage (NT) with and without compost amendment in a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.]–winter wheat (Triticum aestivum L.) and red clover rotation between 2005 and 2010. Wheat yields were not affected by tillage system and averaged 3.80 Mg ha−1 but were 10% higher in compost amended soil compared to no compost. Red clover plant density and dry matter (DM) at cereal grain harvest averaged 127 plants m−2 and 32 g m−2 and were not affected by tillage or amendment treatments. Maximum wheat canopy light interception was attained in late May to early June and ranged from 84 to 91% and typically exceeded 77% light interception for at least 22 d. Red clover root DM increased on average 378% between wheat harvest and 40 d after harvest compared with a 64% average increase in red clover root length. Red clover shoot:root averaged 8.5 at wheat harvest compared with 11.2 40 d after wheat harvest. Producers using this wheat and red clover intercrop should expect no difference in wheat yield or red clover productivity when using IT, MT, or NT.

Maize Debris Increases Barley Yellow Dwarf Virus Severity in North Carolina Winter Wheat

In the eastern United States, wheat (Triticum aestivum L.) is often planted with minimal or no tillage into maize (Zea mays L.) residues. We conducted a field experiment in the North Carolina Piedmont to compare the effects of three maize residue treatments (unchopped, chopped, and removed) on Fusarium head blight (FHB) in two winter wheat cultivars. While FHB levels were too low for meaningful comparisons, severe epidemics of barley/cereal yellow dwarf virus (YDV) did develop in 2 yr out of 3. In those 2 yr, YDV symptoms of discoloration and stunting were greater (P ≤ 0.001), and yield was lower (P ≤ 0.01), in plots with maize residue than in plots without maize residue. In the third year, when planting was late because of a severe fall drought, no YDV epidemic developed, and there were no differences in wheat yield due to maize residue treatment (P = 0.25). In the first 2 yr, leaf samples from all plots were assayed for viruses using a multiplexed reverse transcription polymerase chain reaction (RT‐PCR) method. The most common YDV serotypes were MAV, PAV, and RPV, which were each detected in at least 46 and 74% of samples in the 2 yr, respectively. Our finding of greater YDV severity in association with surface residue is consistent with the reported aphid preference for high‐intensity yellow colors, which we hypothesize attracted aphids preferentially to residue‐covered plots in the fall. Our results support a recommendation of seed or seedling insecticide treatment when planting wheat into heavy unincorporated maize residue in the U.S. Piedmont.

Effect of sowing date and rate on canopy intercepted photo-synthetically active radiation and yield of winter wheat

小麦适期播种不仅是达到全苗壮苗的关键, 还有利于小麦健壮生长发育, 是提高小麦单产的重要措施。本试验研究了不同播期和播量条件下小麦冠层底部光合有效辐射(<i>TPAR</i>)、叶面积指数(<i>LAI</i>)、冠层截获的光合有效辐射(<i>IPAR</i>)等的变化及播期对冬小麦产量的影响。结果表明, 叶面积指数和冠层截获的光合有效辐射随小麦播种时间的推迟而降低, 小麦冠层底部的光合有效辐射随小麦播种时间的推迟而增大。小麦冠层截获的光合有效辐射与叶面积指数呈显著正相关, 相关系数为0.756; 冠层底部的光合有效辐射与叶面积呈显著负相关, 相关系数为-0.872。小麦产量虽然随播期的推迟呈递减趋势, 但10月20日之前播种的小麦产量间无显著差异。因此, 在冬小麦和夏玉米一年两熟区, 可相应推迟小麦的播种时间, 尽量延长上茬玉米的生长期, 以实现两茬作物的均衡增产。

Long‐Term Agronomic Performance of Organic and Conventional Field Crops in the Mid‐Atlantic Region

Despite increasing interest in organic grain crop production, there is inadequate information regarding the performance of organically‐produced grain crops in the United States, especially in Coastal Plain soils of the mid‐Atlantic region. We report on corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.) yields at the USDA‐ARS Beltsville Farming Systems Project (FSP), a long‐term cropping systems trial established in Maryland in 1996 to evaluate the sustainability of organic and conventional grain crop production. The five FSP cropping systems include a conventional no‐till corn–soybean–wheat/soybean rotation (NT), a conventional chisel‐till corn–soybean–wheat/soybean rotation (CT), a 2‐yr organic corn–soybean rotation (Org2), a 3‐yr organic corn–soybean–wheat rotation (Org3), and a 4‐ to 6‐yr organic corn–soybean–wheat–hay rotation (Org4+). Average corn grain yield during 9 yr was similar in NT and CT (7.88 and 8.03 Mg ha−1, respectively) but yields in Org2, Org3, and Org4+ were, respectively, 41, 31, and 24% less than in CT. Low N availability explained, on average, 73% of yield losses in organic systems relative to CT while weed competition and plant population explained, on average, 23 and 4%, respectively, of these yield losses. The positive relationship between crop rotation length and corn yield among organic systems was related to increasing N availability and decreasing weed abundance with increasing rotation length. Soybean yield averaged 19% lower in the three organic systems (2.88 Mg ha−1) than in the conventional systems (3.57 Mg ha−1) and weed competition alone accounted for this difference. There were no consistent differences in wheat yield among cropping systems. Crop rotation length and complexity had little impact on soybean and wheat yields among organic systems. Results indicate that supplying adequate N for corn and controlling weeds in both corn and soybean are the biggest challenges to achieving equivalent yields between organic and conventional cropping systems.

Water-use efficiency of wheat-based rotation systems in a Mediterranean environment

Crop production in Mediterranean-type environments is invariably limited by low and erratic rainfall (200–600 mm year −1), and thus soil moisture, and by high evapotranspiration resulting from high temperature. Consequently, a major research challenge is to devise cropping systems that maximize water-use efficiency (WUE). In a long-term trial in northern Syria (1986–1998) we compared the effects of seven wheat-based rotations on soil water dynamics and WUE in both the wheat and non-wheat phase. The cropping systems were durum wheat ( Triticum turgidum L.) in rotation with fallow, watermelon ( Citrullus vulgaris), lentil ( Lens culinaris), chickpea ( Cicer arietinum), vetch ( Vicia sativa), medic pasture ( Medicago spp.), and wheat. Seasonal recharge/discharge were identified using the neutron probe. Depth of wetting varied with seasonal rainfall (233–503 mm). Based on crop yields, WUE was calculated for each cropping option in relation to the durum wheat crop. The greatest limitation to growth was the supply of water and not the soil moisture storage potential. Wheat grain yield was dictated by the extent to which the alternative crops in the rotation dried out the soil profile, in addition to seasonal rainfall and its distribution. Chickpea and medic extracted as much water as continuous wheat. Wheat after these crops was solely dependent on current seasonal rainfall, but fallow, lentil, watermelon, and vetch did not deplete soil moisture to the same extent, leaving some residual soil moisture for the succeeding wheat crop. This difference in soil water resulted in a significant difference in wheat yield and hence WUE, which decreased in the following crop rotation sequence: fallow, medic, lentil, chickpea, and continuous wheat. However, on the system basis, the wheat/lentil or wheat/vetch systems were most efficient at using rainfall, producing 27% more grain than the wheat/fallow, while the wheat/chickpea system was as efficient as wheat/fallow system, with continuous wheat being least efficient. With N added to the cereal phase, system WUE of the system increased, being least for continuous wheat and greatest for wheat/lentil. Wheat–legume rotation systems with additional N input in the wheat phase not only can maintain sustainable production system, but also are more efficient in utilizing limited rainfall.

Agronomic consequences of tractor wheel compaction on a clay soil

In southern New South Wales, Australia, farming operations using tractors often occur when the soils are moist and prone to soil compaction. However, the extent of soil compaction and its relative impact on crop yield have not been quantified in the region. In this experiment, re-compaction due to tractor wheel traffic in a sodic brown clay (Vertisol) was monitored under simulated controlled traffic conditions after removal of a pre-existing subsoil pan by deep tillage. Soil physical properties under wheel tracks were compared to those between wheel tracks in terms of bulk density, penetrometer resistance, water content, air-filled porosities and changes in “least limiting water range”. Differences in the growth and yield of canola ( Brassica napus) and wheat ( Triticum aestivum) in the two areas were also measured. Although deep ripping increased canola yield by 20% (from 2.0 to 2.4 t ha −1), reformation of a compaction pan under the wheel tracks was already detected in the first season of cropping. In the second cropping year, soil in the 0.05–0.10 m layer under wheel tracks had significantly higher penetrometer resistance (>2000 kPa) and bulk density (1.5–1.58 Mg m −3) and lower air-filled porosity (0.07–0.09 m 3 m −3) compared to that measured between wheel tracks (<1000 kPa and 1.25–1.29 Mg m −3, and 0.187–0.226 m 3 m −3, respectively). The ‘least limiting water range’ was essentially reduced to zero under wheel tracks and hence was unfavourable to plant roots. By contrast, favourable conditions were maintained in the area between wheel tracks throughout the whole available water range. This finding was supported by a significant reduction in canola and wheat root growth in the layer under the wheel tracks. While there was no difference in wheat yield (5.3–5.5 t ha −1), canola grain yield on the wheel track was only 34% of that between wheel tracks (1.1 t ha −1 versus 3.2 t ha −1). The canola results highlight the potential loss in grain yield due to compaction by tractor wheel traffic and indicate the likely benefits of adopting controlled traffic in farming systems for the sodic brown clay soils of this region. However, to fully realise the benefits of controlled traffic on these soil types it may first be necessary to remove the underlying compaction generated by previous farming practices. Conversely, adoption of controlled traffic systems should greatly assist in slowing the rate of recompaction of cropping soils following deep ripping.

Weed seed production, crop planting pattern, and mechanical weeding in wheat

Experiments were carried out to investigate weed seed production in widely spaced spring wheat crops that received aggressive mechanical weed control (hoeing and harrowing) compared with that in narrowly spaced crops receiving less aggressive mechanical control (harrowing only). Three species (wild buckwheat [Polygonum convolvulus], ladysthumb [Polygonum persicaria], and common chickweed [Stellaria media]) were studied in three row-spacing treatments (10, 20, and 30 cm) and two sowing densities (140 and 180 kg ha−1). Average seed production per surviving plant was up to three times higher in the 30-cm treatments compared with the 10-cm treatments. Taking into account the 40–50% weed mortality resulting from control in the 30-cm treatments, seed production per seedling was still higher in the 30-cm treatments than in the 10-cm treatments. Differences in wheat yield were not found among treatments. From the perspective of long-term weed population management, using a narrow row spacing would be more effective in spring wheat on the basis of experiments with the weed species considered here.

Sequential and parallel fodder production in wheat (Wticum aestivum)-based cropping system with special reference to nitrogen economy

A field experiment was conducted during 1988-89 and 1989-90 for obtaining forage for animals and effecting nitrogen economy in wheat (Triticum aestivutn L. emend. Fiori &amp; Paol.)-based cropping system. Sorghum [Sorghum bicolor (L.) Moench] gave significantly higher green fodder (36.0 and 31.7 tonnesiha), dry matter (10.1 and 10.4 tonnesiha) and crude protein (930 and 684 kgiha) compared with cowpea [ V i g ~ unguiculala (L.) Walp.] in both years. However, cowpea gave significantly higher crude protein yield than sorghum in 1988. Wheat grown after cowpea gave significantly higher grain and straw yields than when grown after sorghum. In association with wheaf Egyptian clover (Trifolium alerrmdrinum L.) in border method (in every founhpkipped row) gave 7.7-7.9 tonnesiha green fodder and 1.08-1.31 tonnesiha dry matter without causing significant reduction in wheat yield. The effect of nitrogen on wheat yield was significant and 120 kg Nlha gave significantly higher grain yield than 80 kg Niha. There was a significant interaction between N levels to wheat crop and preceding forage crops in the rainy season. There was no significant difference in wheat yield due to 80 and 120 kg Niha grown after cowpea, whereas after sorghum 120 icg Niha recorded significantly higher grain yield than 80 kg Nha. Therefore, growing of Egyption clover with wheat in every fourth skipped row sequence after cowpea found more productive and remunerative cropping system and economized fertilizer N up to 40 kg Niha without adversely affecting the wheat yield.

Planting pattern in wheat (Triticum aestivum) and Indian mustard (Brassica juncea) crop mixture under irrigated condi- tions in mid-hills of North-Western Himalayas

A field experiment was conducted during the winter season of 1990-91 to 1992- 93 to study the effect of planting pattern of wheat (Triticum aestivum L. emend. Fiori &amp; Paol.) and lndian mustard [Brassica juncea (L.) Czernj. &amp; Cosson] under 2 wheat row spacings (22.5 and 15 cm) and as seed mixture under broadcast sowing. Wheat + lndian mustard intercropped in an 8 : 1 row combination under both wheat row spacings and mixed cropping of wheat and lndian mustard under broadcast sowing system did not show significant difference in wheat yield compared to yield of respec- tive sole crop of wheat. All the inter- and mixed cropping treatments showed higher wheat-equivalent yields, land-equivalent ratio (LER) and benefit :cost ratio over sole crops, and the highest values of these parameters were obtained under planting pattern of wheat and lndian mustard in row ratio of 8 : 1 in both wheat row spacings, but 22.5 cm wheat row spacing proved more remunerative.

Differences in the properties of a red earth after ten years of wheat-lupin and wheat-subterranean clover rotations

2 different rotations, wheat-lupin (WL) and wheat-subterranean clover (WC) were compared under 2 different tillage systems, direct-drilled (DD) and conventional tillage (CT) at a 10-year-old experimental site in Wagga Wagga, New South Wales. Significant differences in soil organic carbon concentration between the 2 rotations were found only under the DD systems; soil under WC rotation had a significantly higher organic carbon in the top 0.05 m than the WL soil. No such difference was detected under CT. Under both tillage systems, WC soil had lower pH (by 0.32 unit), with accompanying lower exchangeable magnesium but higher extractable aluminium than the WL soil in the top 0.05 m. Despite similar earthworm population and surface macroporosity, there was evidence suggesting that, under direct drilling, 10 years of WC rotation had reduced the subsoil water storage after summer fallow and reduced the effective rooting depth of wheat when compared with the WL rotation. These had not resulted in difference in wheat yield between the rotations even though a smaller average grain size was found under WC rotation in the 1990 season.