Reduced Tillage Conditions Research Articles

Side Deep Fertilizing of Machine-Transplanted Rice to Guarantee Rice Yield in Conservation Tillage

Conservation tillage is an environmentally friendly and economical farming method, but its impact on rice yield is controversial. Artificially applied side deep fertilizing of machine-transplanted rice is when fertilizer is applied to the deep soil along with the machine transplantation of rice; this may improve the fertilizer utilization rate and rice yield and eliminate the possible negative effects of conservation tillage on rice yield. Using on machine-transplanted rice, this study aims to compare the effects of side deep fertilizing (SDF). We investigated the effects of artificially applying fertilizer (AAF) on rice growth and yield under conventional tillage (CT), reduced tillage (RT), and no tillage (NT). The rice root activity, root dry weight, leaf area index (LAI), net photosynthetic rate (Pn), chlorophyll content, panicle density, spikelets per panicle, and yield were all ranked as NT > RT > CT and SDF > AAF. The 1000-grain weight was also ranked as SDF > AAF. In addition, under NT conditions, the positive effect of SDF on rice growth and yield was higher than under RT and CT conditions. In general, conservation tillage combined with SDF saved costs and increased rice yield.

Field-scale evaluation of parameters affecting planter vibration in single seed planting

Improving spatial plant uniformity is an important research focus. Planter vibration largely interferes with the seed metering process and thereby affects the planting quality. In this study, a single-seed planter was equipped with a vibration meter to measure the vibration of planter under both conventional and reduced tillage conditions. The experimental stand was established in a complete factorial design with three repetitions; with three different planter speeds and three different furrow opener sizes. The test results showed that the planter vibration linearly increased in parallel to planting speeds and linearly decreased in parallel to furrow opener sizes. The R2 value of each appropriating equation except reduced tillage (RT) at Field_1 and conventional tillage (CT) at Field_2, was greater than 0.90. Planter vibration was lower in planting at RT. The best spatial plant distribution was obtained with a 180 mm furrow opener size and 3.96 km h−1 planting speed. As a result, vibration increased the spatial variability of planting.

The Effect of Subsurface Placement of Mineral Fertilizer on Some Soil Properties under Reduced Tillage Soybean Cultivation

One of the adverse effects of no-tillage is the accumulation of nutrients (in particular P and K) in the top soil layer. The subsurface application of mineral fertilizers at a depth of 10–30 cm can reduce this phenomenon and at the same time provide a relatively uniform access to soil nutrients for plant roots. Such a method of mineral fertilizer application can additionally decrease the environmental risk associated with water eutrophication because the water runoff from fields, where the soil P content is high, is reduced. The aim of this research was to evaluate the effect of the subsurface application of different rates of a compound mineral fertilizer on the content of some macronutrients, soil organic carbon content (SOC), and soil pH in a field after the harvest of soybean grown under reduced tillage conditions. The field experiment was conducted during the growing seasons of 2014/2015–2016/2017 in the village of Rogów, Zamość County, Poland. It was set up as a split-plot design in four replicates. The first experimental factor included two methods of mineral fertilization application: fertilizer broadcast over the soil surface (S); fertilizer applied deep (subsurface placed) using a specially designed cultivator (Sub-S). The other factor was the rates of the mineral fertilizer (NPKS): 85 kg∙ha−1 (F85) and 170 kg∙ha−1 (F170). Over the successive years of the study, the SOC content was found to increase. However, neither the fertilization rate nor the method of fertilizer application caused any significant difference in organic carbon. Under subsurface fertilizer application conditions, a higher soil pH was found in treatment F85, however, when the fertilizer was surface-applied, the soil in treatment F170 had a higher pH value. During the three-year study period, the P and K content in the 0–30 cm soil layer was higher than in the 30–60 cm and 60–90 cm layers. In turn, the highest Mg content was determined in the 30–60 cm layer. In the case of both mineral fertilizer application methods, a higher P content was determined in the soil fertilized at a rate of 170 kg NPKS, compared with a rate of 85 kg∙ha−1. The surface application of the higher rate of mineral fertilization resulted in an increase in the soil K content. On the other hand, when the mineral fertilizer was subsurface-applied, a higher soil K was determined in the treatments with lower mineral fertilization.

Chemical diversity and molecular signature of soil humic fractions used as proxies of soil quality under contrasted tillage management

Increasing food production while avoiding the progressive degradation of agricultural soils has become one of the major challenges at a global level. In consequence, the development of sustainable tillage methodologies or cultivation strategies is an important subject of current research. In fact, it has been observed that the implementation of reduced tillage (RT) vs. traditional tillage (TT) in the long term not only improves soil physicochemical properties but also global soil quality in terms of soil health. In particular, the increase of the soil organic carbon (SOC) content under RT conditions is one of the most important factors, but there is little information about the chemical composition and humification level of this carbon, and thus about its persistence at long-term. This is of particular importance considering the policies of carbon sequestration and climate change mitigation, such as the “4 per 1000” initiative. In this study, molecular-level characterization of the humic acid (HA) and fulvic acid (FA) fractions isolated from a soil after 19 years under RT and TT practices was carried out. This study would provide objective descriptors of the impact of these two tillage practices in the chemical composition of the resulting SOC. With this purpose, the potential of Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR-MS) for assessing changes in the molecular assemblages released from the humic fractions (HA and FA) was examined. The results showed enhanced diversity and chemical richness (expressed as number of molecular formulas) in the composition of SOC under RT. Different tillage-specific compound classes were associated with both tillage practices. As a whole, the humic fraction showed a higher proportion of molecular formulas for lipid and hydroaromatic families in the case of RT compared to TT, while the same fraction under TT showed a greater richness of oxidized protein-derived formulas than RT. In the case of FAs, a similar pattern was observed for hydroaromatic and protein-derived formulas, but the proportion of molecular formulas assigned to unsaturated lipids was higher in TT than in RT. In addition, increased number of formulas for aromatic and condensed aromatic compounds was observed in FAs under TT respect to RT.

Segetal Diversity in Selected Legume Crops Depending on Soil Tillage

The aim of the paper was to determine weed infestation expressed by weeds number and weed weight and other index under a three different tillage system: no-tillage (NT), reduced tillage (RT), and ploughing tillage (CT) in two legume species crops: pea and narrowed-leaved lupine. The research proved that growing legume under no-tillage conditions caused the increasing weed infestation. Weather conditions in each of the study years were shown to influence the weed infestation. The dry weight of weeds was higher in narrow-leaved lupine by 7% in flowering stage assessment and by 6% before harvest than in pea crop. The weeds number in the conventional tillage system in the flowering stage in pea and lupine crops was 24 and 26 plants·m−2, respectively, under the reduced tillage conditions it was 33 and 29% higher, while under no-tillage it was 58 and 67% higher. In all tillage systems the dominant species were Chenopodium album L., Viola arvensis L., Anthemis arvensis L., and Cirsium arvense L. The results prove that soil tillage system affect weed infestation of legume crops.

Impact of insecticide and tillage methods in wheat on the populations of aphid and their coccinellid predators in rice-wheat cropping system of India

The tillage methods are changing in north-western plains of India and conservation tillage is emerging as an important alternative for wheat cultivation. Tillage is known to reduce insect-pests through mechanical damage or burying them deep or bringing them on the surface. The present investigations were undertaken to know the effect of different tillage conditions viz. conventional tillage (CT), Zero tillage (ZT), Zero tillage + mulch (ZT+ mulch) and rotary tillage (RT), on the population build-up of wheat aphids and their natural enemies in rice-wheat cropping system. The aphid incidence was not influenced by tillage type while the population of coccinellid predators increased significantly in all conservation tillage practices. At the same time, the application of insecticide used for aphid control resulted in significant decline of coccinellid predators in reduced tillage conditions. The interactions of insecticide × time indicated that effect of insecticide applied for control of aphids (13 WAS) lasted for 2-4 weeks. More than 12 species of predators and parasitoids of wheat insect pests including coccinellids, syrphid flies, parasitic wasps, spiders and insects belonging to chrysopidae family were recorded under different tillage conditions. Number of coccinellids/m2 in insecticide protected conditions (2.19-2.29) was significantly lower than unprotected ones (2.52-3.55). Significant differences in coccinellids population were also recorded in different tillage conditions. Number of coccinellids/m2 were minimum in CT (1.95-2.27) followed by RT (2.15-2.66), ZT (2.72-3.69) and ZT + mulch (2.80-2.86). Coccinellid population in CT and RT was on par with each other; however, it was significantly lower than in ZT and ZT+ mulch. The results advocate that insecticide application in CT and RT has no effect on incidence of coccinellid population whereas in other tillage conditions application of insecticide significantly reduced their population. Thus, utmost care should be taken while advocating the use of insecticide for aphid control in conservation tillage.

Influences of wide-narrow seeding on soil properties and winter wheat yields under conservation tillage in North China Plain

In order to promote the winter wheat yield and guarantee seeding quality in double-cropping system, no-tillage or reduced tillage planting modes with different row spacing have been implemented to result in different levels of yield. A three-year (2012-2015) field experiment was conducted on the experimental farm at Zhuozhou of Hebei Province in North China Plain to compare winter wheat yield from the two planting modes: wide-narrow row space planting mode (WN) and uniform row space planting mode (UR) Both planting modes were performed under reduced tillage conditions with straw mulching. The results showed that in North China Plain WN had positive impacts on crop yield, yield components, leaf area index (LAI) and intercepted photosynthetically active radiation (IPAR) index. Comparing with the UR, IPAR and LAI index for WN were enhanced by 4.8% and 5.2%, respectively. The average yield for WN was 7.2%, significantly greater than that of UR under the same quantity and density. In addition, for WN mode, machinery could pass through with less blocking under large amount of straw mulching, which largely improved tillage efficiency and potentially popularized the conservation tillage technology in North China plain. It is therefore recommended that wide-narrow row space planting mode (WN) combined with reduced tillage and straw mulching be more suitable for conservation tillage in double-cropping pattern areas in North China Plain. Keywords: winter wheat yield, wide-narrow seeding, conservation tillage, row spacing, LAI, IPAR DOI: 10.25165/j.ijabe.20181104.3399 Citation: Hu H N, Lu C Y, Wang Q J, Li H W, He J, Xu D J, et al. Influences of wide-narrow seeding on soil properties and winter wheat yields under conservation tillage in North China Plain. Int J Agric & Biol Eng, 2018; 11(4): 74–80.

Influences of wide-narrow seeding on soil properties and winter wheat yields under conservation tillage in North China Plain

In order to promote the winter wheat yield and guarantee seeding quality in double-cropping system, no-tillage or reduced tillage planting modes with different row spacing have been implemented to result in different levels of yield. A three-year (2012-2015) field experiment was conducted on the experimental farm at Zhuozhou of Hebei Province in North China Plain to compare winter wheat yield from the two planting modes: wide-narrow row space planting mode (WN) and uniform row space planting mode (UR) Both planting modes were performed under reduced tillage conditions with straw mulching. The results showed that in North China Plain WN had positive impacts on crop yield, yield components, leaf area index (LAI) and intercepted photosynthetically active radiation (IPAR) index. Comparing with the UR, IPAR and LAI index for WN were enhanced by 4.8% and 5.2%, respectively. The average yield for WN was 7.2%, significantly greater than that of UR under the same quantity and density. In addition, for WN mode, machinery could pass through with less blocking under large amount of straw mulching, which largely improved tillage efficiency and potentially popularized the conservation tillage technology in North China plain. It is therefore recommended that wide-narrow row space planting mode (WN) combined with reduced tillage and straw mulching be more suitable for conservation tillage in double-cropping pattern areas in North China Plain. Keywords: winter wheat yield, wide-narrow seeding, conservation tillage, row spacing, LAI, IPAR DOI: 10.25165/j.ijabe.20181104.3399 Citation: Hu H N, Lu C Y, Wang Q J, Li H W, He J, Xu D J, et al. Influences of wide-narrow seeding on soil properties and winter wheat yields under conservation tillage in North China Plain. Int J Agric & Biol Eng, 2018; 11(4): 74–80.

Influences of wide-narrow seeding on soil properties and winter wheat yields under conservation tillage in North China Plain

In order to promote the winter wheat yield and guarantee seeding quality in double-cropping system, no-tillage or reduced tillage planting modes with different row spacing have been implemented to result in different levels of yield. A three-year (2012-2015) field experiment was conducted on the experimental farm at Zhuozhou of Hebei Province in North China Plain to compare winter wheat yield from the two planting modes: wide-narrow row space planting mode (WN) and uniform row space planting mode (UR) Both planting modes were performed under reduced tillage conditions with straw mulching. The results showed that in North China Plain WN had positive impacts on crop yield, yield components, leaf area index (LAI) and intercepted photosynthetically active radiation (IPAR) index. Comparing with the UR, IPAR and LAI index for WN were enhanced by 4.8% and 5.2%, respectively. The average yield for WN was 7.2%, significantly greater than that of UR under the same quantity and density. In addition, for WN mode, machinery could pass through with less blocking under large amount of straw mulching, which largely improved tillage efficiency and potentially popularized the conservation tillage technology in North China plain. It is therefore recommended that wide-narrow row space planting mode (WN) combined with reduced tillage and straw mulching be more suitable for conservation tillage in double-cropping pattern areas in North China Plain. Keywords: winter wheat yield, wide-narrow seeding, conservation tillage, row spacing, LAI, IPAR DOI: 10.25165/j.ijabe.20181104.3399 Citation: Hu H N, Lu C Y, Wang Q J, Li H W, He J, Xu D J, et al. Influences of wide-narrow seeding on soil properties and winter wheat yields under conservation tillage in North China Plain. Int J Agric & Biol Eng, 2018; 11(4): 74–80.

Soil N<sub>2</sub>O emissions under conventional and reduced tillage methods and maize cultivation

The study concerned the determination of nitrous oxide (N<sub>2</sub>O) emissions under conventional and reduced tillage conditions. In the reduced cultivation, a soil cultivating seed drill was used for simultaneous sowing of seeds and subsurface application of fertilizer. The emission levels of the gas tested were dependent on the year of the study and the method of soil tillage, and were subject to considerable changes during the growing season. The use of reduced soil tillage significantly limited emissions of the analysed gas into the atmosphere. Depending on the year of the study, N<sub>2</sub>O emission in the reduced tillage system was from 15% to 40% lower than in the conventional system. Low levels of easily mineralized components in soil could have been the cause of the reduction in N<sub>2</sub>O emissions to the atmosphere.

Impacts of Tillage, Maturity Group, and Insecticide Use on Megacopta cribraria (Hemiptera: Plataspidae) Populations in Double-Cropped Soybean.

Megacopta cribraria (F.), also known as the kudzu bug, is a soybean pest in the United States, and it can cause up to a 60% yield reduction if not controlled. Insecticides are commonly used to manage this pest in commercial soybean fields. However, other soybean production practices may also affect kudzu bug populations. This study investigated the effect of soil tillage, maturity group selection, and insecticide use on kudzu bug densities in soybean. During 2012 and 2013, at two locations each year in North Carolina, four varieties of soybean maturity groups were planted in June into conventionally tilled plots and into plots with cereal crop residue under reduced tillage conditions (mimicking double-crop production). Plots were further split as insecticide-protected and untreated. Four times more kudzu bugs were found in conventionally tilled than reduced till plots throughout the growing season. Selection of the maturity group influenced the attractiveness of the kudzu bug to oviposit on soybean. A 56% reduction of kudzu bug densities was achieved through insecticide treatment, with an ∼6% increase in yield. Information on how production practices, including soil tillage, affect kudzu bug populations in soybean may help growers select practices to minimize kudzu bug injury and protect yield.

No Tillage and Strip Tillage Effects on Plant Performance, Weed Suppression, and Profitability in Transitional Organic Broccoli Production

Organic no-till and strip-till systems have gained attention because of their reported capacity to enhance soil health and suppress annual weeds. This study, conducted at the Horticulture Research Station, Ames, IA, over 2 years (2013–14 and 2014–15) compared a cover crop–based no tillage (NT), strip tillage (ST), and conventional tillage (CT) in transitional organic broccoli (Brassica oleracea L. var. italica) production, with data collected on broccoli yield and quality, plant health, weed suppression, soil temperature, and cost of production. A cover crop mixture of cereal rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth.) was seeded in all plots in September, and was ended by rolling and crimping (NT and ST) or soil incorporation (CT) in late spring the following year. Each whole-plot tillage treatment was split into two subplot fertility treatments—one based entirely on organic preplant granular fertilizer, and the other split between preplant granular fertilizer and postplanting fertigation—to test the effect of fertigation on yield and plant growth under the typically nitrogen (N)-limited reduced tillage conditions. In 2014, yield of broccoli was highest in CT treatments, averaging 5.4 t·ha−1, with no difference between ST and NT treatments. In 2015, yields were equal among tillage treatments, averaging 20.0 t·ha−1. Changing the timing of fertilizer application through the use of fertigation did not affect yield. Weed density and biomass were lowest in the between-row (BR) regions of NT and ST plots in 2014, indicating effective early-season weed suppression. In 2015, NT and ST plots generally had lower weed biomass and density compared with CT plots, but weed growth in BR and in-row (IR) regions of NT and ST plots was similar. Soil temperature was highest in CT plots throughout the year, and higher in ST than in NT plots only during some periods. While production costs did vary slightly across treatments, profit per hectare was most strongly affected by yield. Our findings suggest that cover crop–based organic NT and ST systems may be viable options for organic broccoli growers.

Productivity of selected species of Fabaceae in reduced tillage conditions within a production field

Field experiments were conducted in 2012 and 2013 on farm production fields located in Baborówko (the Wielkopolska voivodeship). The aim of this study was to determine the productivity of plants and also the canopy of white lupine, blue lupine, yellow lupine and pea conducted in the reduced tillage. On the basis of statistical characteristics it can be indicated that the slightest variation was for the number of seeds per pod, the feature whose coefficient variant reached about 5%. In the conditions of observations the lowest seed yield (2.57 t∙ha-1) was obtained in the cultivation of pea. White and blue lupine gave crops in the amount of approximately 3.4 t∙ha-1 and the highest yield reached yellow lupine – almost 3.7 t∙ha-1.

Zmienność zachwaszczenia odmian pszenicy ozimej w zależności od systemu uprawy roli

Summary The aim of this work was the evaluation of winter wheat secondary weed infestation occurring in spring depending on a tillage system and cultivar. The following research parameters were analyzed: factor I – soil tillage system: a) ploughing, b) reduced tillage – cultivating, c) reduced tillage – disc harrow; factor II – winter wheat cultivar: a) Muszelka, b) Ostka Strzelecka, c) Kohelia, d) Satyna. Herbicide Maraton 375 SC was used in autumn at a dose of 4 l/ha. Weed density was evaluated by counting number of weeds in spring, using square-frame method on the 0.25 m 2 . The sum of all individual weed species was analyzed on every treatment set up in 4 replicates during 3 years of studies. Log-linear analysis showed that during the first years of reduced tillage systems, the number of weed per area was significantly higher than in the conventional tillage system. Muszelka cultivar showed the most variable weed infestation in comparison to other winter wheat cultivars. The dominant weed, regardless of the winter wheat cultivar and tillage systems, was Viola arvensis. Moreover, ploughing or reduced tillage conditions were favorable for Fumaria officinalis. However, reduced tillage system, using disc harrow provided optimal conditions for growth of Lamium purpureum.

Corn and Soybean Rotation under Reduced Tillage Management: Impacts on Soil Properties, Yield, and Net Return

A 4-yr field study was conducted from 2007 to 2010 at Stoneville, MS to examine the effects of rotating corn and soybean under reduced tillage conditions on soil properties, yields, and net return. The six rotation systems were continuous corn (CCCC), continuous soybean (SSSS), corn-soybean (CSCS), soybean-corn (SCSC), soybean-soybean-cornsoybean (SSCS), and soybean-soybean-soybean-corn (SSSC). Field preparation consisted of disking, subsoiling, disking, and bedding in the fall of 2005. After the fall of 2006, the raised beds were refurbished each fall after harvest with no additional tillage operations to maintain as reduced tillage system. The surface 5 cm soil from continuous soybean had higher pH than continuous corn in all four years. Unlike pH, total carbon and total nitrogen were higher in continuous corn compared to continuous soybean. Delta 15N tended to be higher in continuous corn compared to continuous soybean. Fatty acid methyl ester (FAME) indicated minor changes in soil microbial community in relation to cropping sequence, however there was a significant shift in rhizosphere community depending on crop. Corn yield increased every year following rotation with soybean by 16%, 31%, and 15% in 2008, 2009, and 2010, respectively, compared to continuous corn. As a result, net returns were higher in rotated corn compared with continuous corn. This study demonstrated that alternating between corn and soybean is a sustainable practice with increased net returns in corn.

Weed Control and Yield Comparisons of Glyphosate- and Glufosinate-Resistant Corn Grown in Rotation

Information on long-term glyphosate- and glufosinate-resistant corn (Zea mays L.) production on weed control and rotation benefits is lacking. A six-year field study was conducted from 2004 to 2009 at Stoneville, MS, to examine the effects of rotating glyphosate-resistant and glufosinate-resistant corn under reduced tillage conditions on weed control, soil weed seedbanks, and yield. The four rotation systems were glyphosate-resistant and glufosinate-resistant corn grown continuously and in rotation with two herbicide programs, post-emergence-only herbicides (POST) and preemergence herbicides followed by POST (PRE + POST). Control of 13 predominant weed species in glyphosate-resistant and glufosinate-resistant corn was >95%, regardless of herbicide program, with the exception of johnsongrass and yellow nutsedge, both perennial weeds. Johnsongrass and yellow nutsedge control was lower in the continuous glufosinate-resistant corn system compared with other rotation systems. Yellow nutsedge control was higher with the PRE + POST (89% to 99%) compared with the POST-only (72% to 86%) treatment. Corn yields were similar regardless of rotation when a corn cultivar stacked with both glyphosate-resistant and glufosinate-resistant traits was used. The PRE + POST program gave 5% to 10% higher yield than the POST-only program in four of six years. The seedbank for yellow nutsedge and predominant grass and broadleaf weeds was not significant among the four rotation systems. Seedbanks for grasses and yellow nutsedge were higher in the POST-only program (20.5 and 1.8 per core of 678 cm3, respectively) compared with the PRE + POST program (9.5 and 0.4 per core, respectively). These results indicate that johnsongrass and yellow nutsedge control could be reduced in continuous glufosinate-resistant corn and could be mitigated by rotating with glyphosate-resistant corn.

Effect of dairy manure slurry application in a no-till system on phosphorus runoff

Incorporation of manure slurry under reduced tillage conditions remains a challenge in the northeastern US. New technologies to directly incorporate slurry are available but their agronomic and environmental benefits have generally not been quantified. This study evaluated the effects of five manure slurry application methods on phosphorus (P) loss in runoff (broadcasting with and without incorporation by tillage, shallow disk injection, banded application and aeration, and pressurized injection) and a control (no manure). Research was conducted over a 2 year period in central Pennsylvania on a well-drained Hagerstown silt loam (fine, mixed, semiactive, mesic Typic Hapludalf) under corn (Zea mays L.) production. Approximately 72 h after dairy (Bos Taurus) slurry application (56,000 l ha−1) to 10 × 13 m plots, a single rainfall simulation (68 mm h−1) was conducted in triplicate on 10 × 2 m areas within the plots. Trends in total P losses in runoff (kg ha−1) from plots varied between years and treatments. Aeration yielded lower losses than all other treatments in 2006 and was amongst the lowest in 2007 with losses statistically similar to shallow disk and pressure injection. Remarkably, few differences were apparent in losses of dissolved reactive P between treatments, reflecting high variability in runoff depths. Indeed, variability in runoff depths resulted in some unexpected trends, including high loads from the unamended control and modest loads from the tillage treatment. Results highlight tradeoffs in alternative manure slurry application practices but point to the potential to significantly lower runoff P losses from reduced tillage systems receiving manure slurry.

Crop residue, manure and fertilizer in dryland maize under reduced tillage in northern China: II nutrient balances and soil fertility

A long-term experiment was carried out in the dryland of northern China to assess the effects of applications of maize stover, cattle manure and NP (1:0.44) fertilizer on partial nitrogen (N), phosphorus (P) and potassium (K) balances, extractable soil N (SEN), P and K, and soil organic matter (SOM) in a spring maize cropping system, under reduced tillage conditions. The experiment was set-up according to an incomplete, optimal design, with three factors at five levels and 12 treatments, including a control with two replications. Statistical analyses using multiple regression models showed that the partial N, P and K balances were strongly influenced by annual variations in the amounts of soil water at seeding (SWS) and growing season rainfall (GSR). Most treatments had positive P but negative N and K balances. Cumulative P and K balances were reflected in extractable soil P (P-Olsen) and K (exchangeable K), but the weak relationships indicated that the sorption of P and buffering of K were strong. Cumulative balances of effective organic carbon (C) were weakly related to soil organic C (SOC) content after 12 years. Negative C balances were related to decreases in SOC, but positive C balances were not translated into increases in SOC. The analysis of nutrient balances and soil fertility indices revealed that nutrient inputs in most treatments were far from balanced. It is concluded that the concepts of ‘ideal soil fertility level’ and ‘response nutrient management’ provide practical guidelines for improving nutrient management under the variable rainfall conditions of dry land areas in northern China.

Effects of green manure use on sweet corn root length density under reduced tillage conditions

A green manure (GM) is a crop grown primarily as a nutrient source and soil amendment for subsequent crops. In environments such as Florida, combined use of GM and reduced tillage may improve soil water and nutrient retention and reduce potential groundwater pollution. In the first 3 years of a long-term experiment, use of GM in a reduced-tillage system on a sandy Florida soil benefited the season-long growth of sweet corn (Zea maysL. var. Rugosa) much more than final ear yields. To help understand these patterns, we evaluated response of sweet corn roots when in rotation with GM of sunn hemp (Crotalaria junceaL.; summer) and cahaba white vetch (Vicia sativaL.; winter 2002–2003) and a multi-species mixture of hairy vetch (V. villosaRoth.) and cereal rye (Secale cerealeL.; winter 2003–2004). Treatments included sweet corn with combinations of 0 or 133 kg chemical N ha−1(as NH4NO3) and with or without GM. A highly fertilized treatment (267 kg chemical N ha−1) without GM was also included. Soil cores were sampled from three depths (0–15, 15–30 and 30–60 cm) both between and within corn rows. Data from two experiments showed that use of GM increased sampled corn root length density (RLD) by 44–54%, although only within the upper 15 cm of soil in one of the two experiments. Corn following GM plus 133 kg chemical N ha−1produced up to 44% greater RLD than corn with 267 kg chemical N ha−1. Sampled RLD decreased with distance away from corn plants (from in-row to between-row positions, and from shallow to deeper depth), with roughly 85–95% of sampled RLD existing in the top 30 cm of soil across all treatments. During the 2004 experiment, we found that broadcast, as opposed to banded (placed along corn row only), chemical N application resulted in more even distribution of corn RLD between in-row and between-row positions during late-season without regard to GM crop. Although GM permitted optimal sweet corn growth with a 50% reduction in chemical N application, ear fill during the final 1–2 weeks before harvest may have been reduced in GM treatments. GM effects on the amount and spatial distribution of sweet corn RLD may help explain these trends. Provision of greater N from GM residues and/or altered distribution of supplementary chemical N and irrigation may be required to achieve greater ear yield benefit from GM.

Cotton and corn rotation under reduced tillage management: impacts on soil properties, weed control, yield, and net return

A 6-yr rotation study was conducted from 2000 to 2005 at Stoneville, MS to examine the effects of rotating glyphosate-resistant (GR) and non-GR (conventional) cultivars of cotton with corn under reduced tillage conditions on soil properties, weed control, crop yield, and net return. There were four rotation systems (continuous cotton, continuous corn, cotton–corn, and corn–cotton) for each non-GR and GR cultivar arranged in a randomized complete block design with four replications. Field preparation consisted of disking, subsoiling, disking, and bedding in the fall of 1999. After the fall of 2000, the experimental area received no tillage operations except rebedding after harvest each year to maintain reduced tillage conditions. A glyphosate-based program in GR cultivars and a nonglyphosate-based program in non-GR cultivars were used for weed management. Soil organic carbon in the top 5-cm depth progressively increased from the first year to the sixth year, regardless of rotation. In 2005, organic carbon was higher in corn grown continuously and in rotation compared to continuous cotton, partly due to higher plant residues from corn compared to cotton. Control of most grass and broadleaf weeds was sufficient to support cotton and corn production, regardless of rotation and herbicide program. Control of yellow nutsedge was reduced in continuous non-GR cotton; this apparent weed species shift toward yellow nutsedge was mitigated by breaking the cotton monocrop with corn. Plant populations of both GR and non-GR cotton rotated with corn were similar to that of continuous cotton suggesting cotton stand establishment was not affected by corn residues from the previous year. Cotton yield increased every year following rotation with corn by 10–32% in the non-GR cultivar, and by 14–19% in the GR cultivar compared to continuous cotton. Similarly, corn yield increased by 5–13% in non-GR cultivar and by 1–11% in the GR cultivar when rotated with cotton. As a result, net returns were higher from rotation management as compared with monoculture in both crops. This study demonstrated that alternating between cotton and corn is agronomically feasible and a sustainable option for farmers in the lower Mississippi River alluvial flood plain region who are looking for simple cultural practices that provide economic and environmental benefits.