Fallow Yield Research Articles

Increased pepper yields following incorporation of biofumigation cover crops and the effects on soilborne pathogen populations and pepper diseases

The use of brassica cover crops and their associated degradation compounds as biofumigants to manage soilborne pathogens could offer vegetable growers an alternative to the restricted broad-spectrum fumigant methyl bromide. Biofumigation was tested in two experiments to manage Rhizoctonia solani, Sclerotium rolfsii, and Pythium spp., and the diseases they cause on pepper. Field plots were seeded in fall 2010 and spring 2011 to oilseed radish (Raphanus sativus L.), ‘Pacific Gold’ mustard (Brassica juncea (L.) Czern), or ‘Dwarf Essex’ winter rapeseed (Brassica napus L.). Cover crops were disked into soil in spring 2011 and immediately covered with virtually impermeable film (VIF) to reduce the escape of volatile pesticidal compounds. Controls included fallow plots with (CVIF) and without (fallow) VIF. Green bell pepper was transplanted into all plots. Concentrations of isothiocyanates (ITCs), the brassica degradation compounds primarily responsible for pesticidal activity, were highest following incorporation of mustard. Rapeseed yielded the second highest ITC concentrations. Radish yielded very low ITC concentrations in experiment 1, and none during experiment 2. ITCs also were detected in low concentrations in CVIF treatments. All treatments that received VIF reduced populations of R. solani compared to fallow, with no differences between biofumigation treatments and CVIF. Biofumigation treatments did not reduce populations of Pythium spp. or S. rolfsii compared to CVIF. Pepper stunting was significantly lower in treatments that received VIF compared to fallow, with no consistently significant differences between biofumigation treatments and CVIF. Pythium isolated from roots of stunted peppers was identified as Pythium aphanidermatum. Biofumigation treatments did not reduce plant mortality. Pepper yields were highest in biofumigation treatments compared to CVIF, and CVIF yields were higher than fallow yields.

Bunch yield response of two cultivars of plantain (Musa spp., AAB, Subgroups French and False horn) to hot-water treatment and fertilizer application planted after forest and bush/grass fallow

Effects of fallow type, sucker sanitation (hot-water treatment, HWT) and fertilizer application on yield, root and corm health of two plantain cultivars were investigated. Most yield parameters were strongest affected by fallow type with more producing plants, higher bunch mass and yield after forest clearing than in bush/grass fallow. The second most important factor was HWT with more producing plants (52.3%) than in control (35.8%, p < 0.0001). Fertilizer application increased the proportion of producing plants by 9%, p < 0.018 and yield from 4.08–5.79 Mg ha−1. Combined HWT and fertilizer had strong synergistic effects. Cultivar interacted with fallow and HWT: in bush/grass fallow yield did not differ between cultivars (2.17 Mg ha−1); in forest fallow Essong produced 57% (9.4 Mg ha−1) more than Ebang (6.0 Mg ha−1, p < 0.001). Essong yielded 65% more after HWT than Ebang (8.0 versus 4.9 Mg ha−1, p < 0.001), yet not when untreated. A limited sink capacity of Ebang is likely to constrain yield increases. HWT improved root and corm health and was better in forest than in bush/grass land. In bush/grass fallow no treatment attained yields as high as in forest even when untreated and not fertilized. Soil chemical properties were not correlated with yield.

Fertilizer and rhizobial inoculant responses of chickpea on fallow and stubble sites in southern Alberta

Agronomic practices for chickpea (Cicer arietinum L.) production on the Canadian prairies are not well established. The objective of this study was to evaluate the impact of fallow on chickpea yield and response to rhizobia inoculation and fertilization. Field trials were conducted at nine fallow sites and nine stubble sites in southern Alberta over a 4-yr period (2000–2003). In the N experiment, N fertilizer was applied to rhizobia-inoculated and uninoculated desi (cv. Myles) and kabuli (cv. Sanford) chickpea at five N rates (0, 20, 40, 60 and 80 kg N ha-1). In the P experiment, P fertilizer was applied to desi chickpea at 0, 6.5 and 13 kg P ha-1. Growing season precipitation was well below normal during 3 of the 4 yr of this study, and fallow yields were more than double stubble yields. Desi seed yield increased 15.8 kg ha-1 for each millimetre increase in water use above a minimum requirement of 84 mm. Although nodulation of uninoculated chickpea was absent or very low at all sites, the benefits of inoculation were modest. On average, inoculation increased seed yield by 12%, seed protein concentration by 11%, and seed N yield by 24%. Inoculation responses were similar for fallow and stubble sites. Yield gains due to application of N fertilizer were also small at most sites, with no difference in yield gain between fallow and stubble sites. Yield benefits due to inoculation and N fertilization were often small because either moisture availability was low or soil N availability was high. Desi was more responsive to N fertilization than kabuli. Phosphorus fertilizer had a minimal impact on desi chickpea yield. Fallow had a large impact on chickpea yields, but did not affect rhizobia or fertilizer response. Key words: Cicer arietinum, yield, nitrogen, phosphorus, water use efficiency

A straw mulch system to allow continuous wheat production in an arid climate

Cereal Cyst Nematode (CCN, Heterodera avenae Woll.) has been shown to be a devastating pest for wheat ( Triticum aestivum L.) in dryland regions. Fallowing in the season preceding the cropping season has been hypothesized to sanitize the soil of CCN and allow wheat production. This paper explores management options that might allow the continuous production of wheat in these regions. In a 20-year study in the Negev, Israel, on a sandy loam, loessial, soil, it was found that in those seasons with high rainfall there was virtually no decrease in annual wheat yields for continuous crops as compared to biennial fallow yields obtained with the conventional wheat system. The hypothesis that high soil water content substantially alleviates the damage resulting from CCN infestation was confirmed in a pot study. A practical solution for maintaining high soil water content in the field was to leave a straw mulch on the soil surface to decrease soil evaporation. A chopper was added to a grain harvester to finely chop the straw so that it settles to the soil surface through the stubble, and a no-till drill was used for sowing through the straw. The straw-mulch system was shown to result in annual yields from continuous wheat that were equivalent to yields in alternate years with the conventional fallow wheat system, thereby doubling wheat production in this dryland region.

FIRST 12 YEARS OF A LONG-TERM CROP ROTATION STUDY IN SOUTHWESTERN SASKATCHEWAN — YIELDS AND QUALITY OF GRAIN

Yield and quality of spring wheat in particular, and of flax, fall rye, and oat hay, in general, in 12 rotations deemed feasible for southwestern Saskatchewan, were summarized and discussed after the first 12 yr of a long-term rotation study. The study was conducted on a Brown Chernozemic loam. The factors examined were the effect of rotation length, fallow-substitute crops, and N and P fertilizer. On a crop-year basis, continuous wheat yields averaged 75% of fallow yields when recommended rates of N and P fertilizers were applied. Yield variability was lower for rotations that included high proportions of fallow than for continuous-type rotations. Fertilizer N applied at recommended rates increased yields of wheat grown on fallow by an average 5% (from 1780 to 1860 kg∙ha−1) and wheat grown on stubble by an average 7% (from 1350 to 1455 kg∙ha−1). Application of P fertilizer at recommended rates increased yields of wheat grown on fallow and stubble by an average 12%. Total wheat production (kg∙ha−1∙yr−1) was inversely related to the frequency of fallow in the rotation. Thus, continuous wheat (N and P applied) outproduced wheat grown on fallow in the 2-yr rotation by 53% over the 12-yr period. Wheat yields were directly related to growing season rainfall. Flax yields were generally poor because of their low drought tolerance and poor ability to compete with weeds. Fall rye yields were generally higher than provincial averages because the soil used in this study was more fertile than those in which rye is normally grown. Protein concentrations of wheat grown on fallow were high (average 15.9%) and generally greater than that of wheat grown on stubble (except for wheat grown on flax stubble). Failure to apply N fertilizer to continuous wheat resulted in the lowest grain protein (average 13.5%). P concentrations of wheat grown on stubble were greater than that for wheat grown on fallow due to P dilution by yield. The P concentration in wheat was directly related to rainfall. The volume weight of wheat was not greatly influenced by treatment and was above the base criterion of 74.5 kg∙hL−1 in all years.Key words: Crop rotations, grain yields, protein, yield-rainfall interaction, grain quality, fertilizer effects

EFFECT OF SUMMERFALLOWING AND ROTATION ON YIELD OF WHEAT, BARLEY AND FLAX

Yields of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and flax (Linum usitatissimum L.) were studied in various rotations over a 13-year period. During this time precipitation averaged about 10% below long term means. Wheat yields in the second year after fallow averaged about 75% of the yield in the first year after fallow, and were more variable. Continuous wheat failed in 2 years out of 13 because of excessive competition from weeds. Because of these failures, continuous wheat yields were extremely variable and averaged 55% of fallow yield. Barley performed in much the same way as wheat, except that the yield of barley was no more erratic on stubble land than on fallow. Wheat and barley yields were unaffected by other crops growing in 3-year rotations. Flax yields were depressed following flax, whether a year of fallow intervened or not. Alfalfa (Medicago sativa L.) depressed wheat yield in the first crop after breaking, even though a full year of summerfallow preceded the wheat. Alfalfa with bromegrass (Bromus inermis Leyss.), and bromegrass alone, did not affect wheat yields significantly.