Crop Rotation Cycle Research Articles

Past organic fertilizer treatments: Influence on the herbicide diflufenican soil metabolism in wheat crops

The influence of several organic fertilizer treatment regimens, applied at the beginning of crop rotation cycles, were compared as to their slowing down effect on the herbicide diflufenican soil metabolism in wheat crops. In a first trial made at the site ''Longs Tours'', the organic fertilizers treatment schemes had been repeatedly applied in the past since 30 years, according to a 3 years rotation cycle. The following organic fertilizers treatment regimens were compared: treatment (1) no organic fertilizer at all; treatment (2) cow manure; treatment (3) pig slurry + green manure + crop wastes; treatment (4) green manure + crop wastes; treatment (5) straw cereal wastes alone. A spring wheat crop was sown and diflufenican was applied, i.e. 1.6 years after the latest external organic fertilizers application. During the 4 first crop months, the diflufenican soil half-lives were 59, 91, 117, 81 and 70 days in the treatments 1, 2, 3, 4 and 5 treated plots, respectively. During the end period of the crop, the effect of the organic fertilizers treatments disappeared, the diflufenican and its metabolites soil concentrations becoming very low and similar in the organic fertilizers treated and untreated control plots. A second trial was made with winter wheat at the site ''Les Pompes''. The organic fertilizers regimens however had been applied only one time 1.2 years before sowing and diflufenican application. In this trial, the organic fertilizers treatments had no significant influence on diflufenican soil half-life.

Effect of rice based six multiple cropping sequences under two cycles of crop rotations on yield and fertility status of soil

A field experiment was carried out to study the effect of various crop rotations, of high yielding varieties of cereals, pulses, fodders, tubers and oilseeds, on the performance of the crops and the fertility status of the soil over two crop-rotation cycles. The yields of rice (Oryza saliva L.), potato (Solanum tuberosum L.) and onion (Allium cepa) crops were found to be decreasing. The yields of wheat (Triticum aestivum L.) and mustard (Brassica juncea coss), were not affected, while the yield of moong (Phaseolus aureus Roxb.) showed a tendency to increase. Rotations which included berseem (Trifolium alexandrinum) increased the organic carbon content of the soil and there was a slight lowering of the pH with the highest application of phosphatic fertilizer. The accumulation of available potassium was greater in the treatments where the highest amount of fertilizer was applied. The available nitrogen content of the soil increased with application of nitrogen and the balance sheet of nitrogen, phosphorus and potassium showed a positive trend. The continuous cropping of high yielding varieties showed a reduction in the available zinc and iron status of the soil, whereas available manganese and copper increased. The available micronutrients, except manganese, did not correlate significantly with soil pH.

Cropping Frequencies to Sustain Long‐Term Conservation Tillage Systems

AbstractConservation tillage technologies are essential to develop long‐term alternative agriculture approaches to protect the nation's resources. This study was conducted to develop long‐term multiple cropping systems to sustain conservation crop production. Soybean [Glycine max (L.) Merrill] and grain sorghum [Sorghum bicolor (L.) Moench] cropping sequences following wheat (Triticum aestivum (L.) grain harvest were studied at three tillage‐intensity levels on a Cecil sandy loam (clayey, kaolinitic, thermic Typic Hapludult) soil. During the first 4‐yr crop rotation cycle, coulter in‐row chisel (MT) planted grain sorghum produced significantly more grain than either coulter (NT) or disk harrow (CT) planted (4.89 vs. 4.58 and 4.39 Mg ha−1), without a crop‐rotation response. In the second 4‐yr cycle, the sorghum grain yields declined NT > MT > CT (5.14 > 4.74 > 4.40 Mg ha−1) significantly with each increase in tillage‐intensity level. Soybean responded consistently and significantly to high‐frequency (1:1) rotation with grain sorghum. These responses to rotation with grain sorghum become less important to conservation tillage systems when favorable rainfall distributions permit grain yields that range between 2.00 and 3.50 Mg ha−1. Wheat yields increased significantly following soybean (first rotation cycle) until take‐all (Graeumannomyces graminis) became epidemic. Elucidation of significant grain sorghum responses to in‐row chisel and coulter conservation tillage during the first and second crop‐rotation cycles, respectively, requires additional research that focuses on characterization of temporal changes in the soil environment. Rotation of both cool‐ and warm‐season crops is necessary to sustain long‐term conservation tillage.

Weed Seed Bank and Vegetation at the Beginning and End of the First Cycle of a 4-Course Crop Rotation with Minimal Weed Control

Maize water suitability (MWS) model was developed at growth stage scale. Frequency and severity of drought were evaluated by combining MWS estimates and agricultural meteorological drought indexes. The MWS at each growth stage was calculated by using maize observational data and conventional meteorological data at 52 sites in Liaoning during the period from 1981 to 2010. Based on the climatic trend and abrupt change analysis, spatiotemporal dynamics of MWS were investigated. Meanwhile, occurrence of agricultural drought and its severity were also estimated. The results showed that the variation of MWS largely differed at different growth stages. Climatic abrupt change happened in 1994, 1996 and 1999 at the stages of emergence to seven leaves (II), jointing to tasseling (IV) and physiological maturity to maturity (VI). During the past 30 years, MWS showed an obvious increasing trend at the stages of sowing to emergence(I) , seven leaves to jointing(III), IV and tasseling to physiological maturity(V), while it showed a decreasing trend at the stages of II and VI, and that at VI stage was statistically significant. In addition, the climatic trend of MWS showed apparently spatial variability. The frequencies of drought at different severities varied with maize growth stages. Areas of high variability of MWS were located in the Northwest and South of Liaoning at the stages of I , II , III and VI, where were also the regions of high frequency of mid- and severe-drought. At the stages of IV and V, the frequency of drought was low and only light- and mid-drought occurred in few areas. In conclusion, the regional mean MWS could be capable to reasonably assess the agricultural drought in Liaoning at the regional scale.

Nitrogen in West Africa: The Regional Cycle

We have calculated a nitrogen cycle budget for West Africa south of the northern Sahara that quantifies biologically important pools of nitrogen in the region and major fluxes associated with these pools. Major compartments of our model include noncultivated systems broken down by vegetation zone, successional status, and plant components; annual and perennial crops each broken down by crop species and plant and harvest components; wetlands; anthropic systems; and soils and sediments. Base reference year is 1978. Biological nitrogen fixation and precipitation fluxes dominated nitrogen inputs to West Africa in 1978. Approximately 12 × 109 kg were fixed in noncultivated systems; about half of this was fixed in early successional (0—6 yr) rain forests, and much of the rest in grazed or fallow savanna grasslands and woodlands. Less than 0.7 × 109 kg were fixed in cultivated systems; legumes accounted for ≈25% of this. Total anthropic sources (fossil fuel combustion, fertilizer production, and agricultural commodity imports) were minor (<0.3 × 109 kg). Precipitation inputs to the region were ≈0.4 × 109 kg. Most nitrogen leaving West Africa did so volatilized by fire (≈8.3 × 109 kg), principally in non—cropped systems. Major losses also occurred via hydrologic export to the Atlantic Ocean (1.5 × 109 kg) and via denitrification (1.1 × 109 kg). Total N losses from West Africa exceeded 11.0 × 109 kg. The nitrogen immobilized in growing woody vegetation appeared to have amounted to ≈5.6 × 109 kg. Most was immobilized in forested regions by vegetation regrowth during the fallow phase of the bush fallow crop rotation cycle, the dominant cropping system in West Africa. A very small amount was immobilized by perennial crops such as cacao and rubber. Net immobilization in soil was not estimated; total soil N was assumed to be in steady state for the region as a whole. Our overall budget balances within 1%, despite independent calculations of all major fluxes. The balance portrays a nitrogen cycle dominated by pools and fluxes in noncropped systems. In contrast to N balances in developed regions, direct anthropic fluxes are a minor part of the West Africa cycle. Indirect human influences, however, mainly through effects on vegetation cover, appear to be a major determinant of both the rates at which nitrogen is cycled in West Africa and the relative importance of most pools and fluxes.