Influence of time and method of alfalfa stand termination on yield, seed quality, N uptake, soil properties and greenhouse gas emissions under different N fertility regimes

Abstract

A field experiment was conducted in a 7-year old alfalfa stand to compare the influence of time and method of terminating alfalfa stands on crop yield, seed quality, N uptake and recovery of applied N for wheat (Triticum aestivum L.) and canola (Brassica napus L.), soil properties (ammonium-N, nitrate-N, bulk density, total and light fraction organic C and N), and N 2 O emissions on a Gray Luvisol (Typic Cryoboralf) loam near Star City, Saskatchewan, Canada. The treatments were a 3 9 3 9 4 factorial combination of three termination methods [herbicide (H), tillage (T), and herbicide ? tillage (HT)], three termination times (after cut 1 and cut 2 in 2003, and in spring 2004) and four rates of N (0, 40, 80 and 120 kg N ha -1 ) applied at seeding to wheat-canola rotation from 2004 to 2007.In the termination year, soil nitrate-N was considerably higher in T or HT treatments than in the H treatment and decreased with delay in termination. In the first crop year, seed and straw yields of wheat grown on T and HT treatments were significantly greater than H alone (by 1,055-1,071 kg seed ha -1 and by 869-929 kg straw ha -1 ), due to greater content of soil available N in T treatments. Yields decreased with delay in termination time. In general, yield and N uptake in seed and straw, and protein concentration tended to increase with increasing N rate. A greater yield increase occurred on the H compared to T and HT treatments from the first increments of N applied. Nitrous oxide emissions were generally low and there were no treatment differences evident when cumulative 4-year N 2 O-N losses were compared. Appropriate N fertilization was able to compensate for yield reductions due to delayed termination timing, but could not do so entirely for yield reductions on the H compared to T or HT termination method. The amounts of TOC, TON, LFOC and LFON after four growing seasons were usually higher or tended to be higher under H treatment than under T treatment in the 0-5 cm soil layer, but the opposite was true in the 5-10 cm or 10-15 cm soil layers.

Sludge Biochar Amendment and Alfalfa Revegetation Improve Soil Physicochemical Properties and Increase Diversity of Soil Microbes in Soils from a Rare Earth Element Mining Wasteland

“…A similar trend was also observed in the bulk density of four treatments, with those of G, SBC, and SBCG significantly lower than that of CK ( p < 0.05) by 9.1%, 5.6% and 14.7%, respectively. The lower levels of specific gravity and bulk density in treated soils (G, SBC, and SBCG) suggested that sludge biochar application and alfalfa revegetation both significantly reduced soil compaction and enhanced soil porosity and ventilation, which are attributed to the porous structure of the sludge biochar [ 18 ] and the strong root system of alfalfa [ 48 , 49 ]. Total porosity only showed significant differences between CK and SBCG ( p < 0.05).…”

“…Many studies have demonstrated that the use of biochar can significantly increase soil organic C [ 64 , 65 ], mineral nutrient content (e.g., N, P, K) [ 66 ] and the cation exchange capacity of soil [ 18 ] for its carbon-rich and porous structure [ 56 ] and huge specific surface area [ 67 ]. Increasing quantities of data have shown that alfalfa revegetation can significantly increase soil soil organic carbon and total nitrogen concentrations present in the root ball [ 68 ], C/N ratio [ 57 ], porosity, aeration conditions, and water-holding capacity [ 49 ], all of which could accelerate the mineralization of organic carbon and the release of mineral nutrients from sludge biochar, and in turn promote the alfalfa growth. In the present study, an additive effect on soil chemical properties, like that of soil physical properties, was also detected when combined sludge biochar amendment and alfalfa revegetation ( Figure 2 ).…”

Impacts of 49–51 years of fertilization and crop rotation on growing season nitrous oxide emissions, nitrogen uptake and corn yields

“…This may not be the case for dry soils in semi-arid climates, however, as Malhi et al (2010) found very low N 2 O emissions (ranging from 0.16 to 0.62 kg N 2 O ha…”

Tillage method and glyphosate‐resistant alfalfa termination timing affect soil properties and subsequent corn yield

“…To mitigate these negative effects, growers have been moving to conservation tillage practices such as no‐till and strip‐till. These systems leave more plant residue on the soil surface, preserve soil structure, decrease the potential for erosion (Moyer, Clapperton, & Boswall, 2003), improve soil moisture, decrease nitrate (NO 3 − ) leaching, and decrease nitrous oxide greenhouse emissions (Malhi, Lemke, & Schoenau, 2009). However, compared with conventional tillage systems, no‐till systems can have greater compaction (Vyn & Raimbult, 1993), reduced corn emergence rates (Al‐Darby & Lowery, 1987; Licht & Al‐Kaisi, 2005), and lower corn yield (Aflakpui, Vyn, Hall, Anderson, & Swanton, 1993).…”