Ghulam Abbas Shah

Simulation of Long-Term Carbon and Nitrogen Dynamics in Grassland-Based Dairy Farming Systems to Evaluate Mitigation Strategies for Nutrient Losses.

Many measures have been proposed to mitigate gaseous emissions and other nutrient losses from agroecosystems, which can have large detrimental effects for the quality of soils, water and air, and contribute to eutrophication and global warming. Due to complexities in farm management, biological interactions and emission measurements, most experiments focus on analysis of short-term effects of isolated mitigation practices. Here we present a model that allows simulating long-term effects at the whole-farm level of combined measures related to grassland management, animal housing and manure handling after excretion, during storage and after field application. The model describes the dynamics of pools of organic carbon and nitrogen (N), and of inorganic N, as affected by farm management in grassland-based dairy systems. We assessed the long-term effects of delayed grass mowing, housing type (cubicle and sloping floor barns, resulting in production of slurry and solid cattle manure, respectively), manure additives, contrasting manure storage methods and irrigation after application of covered manure. Simulations demonstrated that individually applied practices often result in compensatory loss pathways. For instance, methods to reduce ammonia emissions during storage like roofing or covering of manure led to larger losses through ammonia volatilization, nitrate leaching or denitrification after application, unless extra measures like irrigation were used. A strategy of combined management practices of delayed mowing and fertilization with solid cattle manure that is treated with zeolite, stored under an impermeable sheet and irrigated after application was effective to increase soil carbon stocks, increase feed self-sufficiency and reduce losses by ammonia volatilization and soil N losses. Although long-term datasets (>25 years) of farm nutrient dynamics and loss flows are not available to validate the model, the model is firmly based on knowledge of processes and measured effects of individual practices, and allows the integrated exploration of effective emission mitigation strategies.

Effect of storage conditions on losses and crop utilization of nitrogen from solid cattle manure

The objectives of the present study were to quantify the effects of contrasting methods for storing solid cattle manure on: (i) total carbon (C) and nitrogen (N) balances during storage, and (ii) crop apparent N recovery (ANR) following manure application to arable land, with maize as a test crop. Portions of 10 t of fresh solid cattle manure were stored for 5 months during 2009/10 in three replicates as: (i) stockpiled heaps, (ii) roofed heaps, (iii) covered heaps and (iv) turned heaps at Wageningen University, the Netherlands. Surface emissions of ammonia (NH 3 ), nitrous oxide (N 2 O), carbon dioxide (CO 2 ) and methane (CH 4 ) were measured regularly using a static flux chamber connected to a photo-acoustic gas monitor. Total C and N losses during storage were determined through the mass balance method. After storage, the manures were surface-applied and incorporated into a sandy soil, and maize ANR was measured as a proportion of both N applied to the field (ANR F ) and N collected from the barn (ANR B ). During the storage period, the average losses of initial total N (N total ) were 6% from the covered, 12% from the roofed, 21% from the stockpiled and 33% from the turned heaps. Of the total N losses, 2–9% was lost as NH 3 -N, 1–4% as N 2 O-N and 16–32% through leaching. However, the greatest part of the total N loss from the four storage methods was unaccounted for and constituted in all probability of harmless dinitrogen gas. Of the initial C content, c. 13, 14, 17 and 22% was lost from the covered, stockpiled, roofed and turned heaps, respectively. Maize ANR F was highest from covered (39% of the applied N) followed by roofed (31%), stockpiled (29%) and turned manure (20%). The respective values in case of maize ANR B were 37, 27, 23 and 13%. It is concluded that from a viewpoint of on-farm N recycling the storage of solid cattle manure under an impermeable plastic cover is much better than traditional stockpiling or turning heaps in the open air.

Improvements in wheat productivity and soil quality can accomplish by co-application of biochars and chemical fertilizers

The beneficial role of biochar is evident in most of infertile soils, however this is argued that increment in crop yield owing to biochar application does not always achieve in cultivated/fertile soils. The nutrient biochar believed to enhance crop yield and soil fertility than structural biochar that may offset the positive effect of chemical fertilizer on crop performance but improves soil structural properties. Therefore, we investigated the effect of biochars [produced from nutrient rich feedstocks like poultry manure (PMB) and farmyard manure (FMB) and structural feedstocks such as wood chips (WCB) and kitchen waste (KWB)], and chemical fertilizers (CF) when applied alone or in combination on soil chemical properties, wheat growth, yield and nitrogen uptake in a cultivated clay loam soil. Sole biochar treatments increased the total carbon and mineral nitrogen content that were 21 and 106% higher, respectively compared to control after 128days (P<0.001). Contrarily, sole biochars application did not increase wheat biological yield and N uptake compared to control (P>0.05) except PMB, the nutrient biochar (P<0.05). Compared to control, grain yield was 6 and 12% lower in WCB and FMB, respectively but not differed from KWB, PMB or WCB-CF. Conversely, co-application of biochars and CF treatments increased crop biological yield but the increment was the highest in nutrient biochars FMB or PMB (29 or 26%), than structural biochars WCB and KWB (15 and 13%), respectively (P<0.05). For N uptake, this increment varies between 16 and 27% and again nutrient biochar has significantly higher N uptake than structural biochars. Hence, nutrient biochars (i.e. PMB) benefited the soil fertility and crop productivity more than structural biochars. Therefore, for immediate crop benefits, it is recommended to use nutrient biochar alone or in combination with chemical fertilizer. Such practice will improve crop performance and the quality of cultivated soil.

Maize nitrogen recovery and dry matter production as affected by application of solid cattle manure subjected to various storage conditions

This study aimed to quantify the effects of contrasting composted methods of solid cattle manure (SCM) ondry matter (DM) yield and crop apparent N recovery (ANR)following manure application to maize land. Fresh SCM was stored as stockpiled, roofed, covered and composted heaps. After storage, the manures were incorporated in a sandy soil, and maize ANR both as a proportion of field applied N (ANRF) and collected N from the barn (ANRB),and DM yield was established at three successive growth stages: end of juvenile phase, start of grain filling, and physiological maturity. During the storage period, on average 6% of the initial Ntotal was lost from covered, whereas this fraction was 12, 21 and 33% from roofed, stockpiled, and composted heaps, respectively. DM yield of maize increased with the application of all the manure types as compared to the unfertilized control, at the end of Juvenile (2.2 vs. 3.1-3.4 Mg ha-1), grain filling (11.2 vs. 13.6-16.4 Mg ha-1) and physiological maturity stages (13.9 vs. 15.3-15.9 Mg ha-1). At a given growth stage, the greatest value was obtained from covered than roofed, stockpiled and composted manures.Maize ANRF was the highest at start of grain filling (20, 29, 31, and 39% of the applied N for composted, stockpiled, roofed and covered treatments, respectively) but lower values were obtained at physiological maturity (12-21%). The respective values in case of maize ANRB were 13, 23, 27 and 37% of total N taken from barn at the start of grain filling while it was also lower (8-20%) at physiological maturity. It is concluded thatstorage of SCM under an impermeable plastic cover reduce N losses, increased DM yield and ANR thereby improves on-farm N cycling as compared to traditional stockpiling or composting.

ZnO nanoparticles and zeolite influence soil nutrient availability but do not affect herbage nitrogen uptake from biogas slurry

Recently, there is a growing interest among agriculturists to use nanotechnology for the development of nutrient-use efficient fertilizers. However, its sustainable use for the synthesis of mineral or organic nano-fertilizers requires a thoughtful of the mechanism as well as the fate of nutrients and their interaction with soil-plant systems. Therefore, the aim of current study was to investigate the mixing of three different application rates of zinc oxide nanoparticles (ZNPs: 1.4, 2.8 and 3.6 mg kg-1 soil) as well as zeolite (141, 282 and 423 mg kg-1 soil) with biogas slurry (AS) on soil nutrient availability and herbage nitrogen (N) and zinc (Zn) uptake in a standard pot experiment. We found that both ZNPs and zeolite significantly increased mineral N content in soil compared to AS alone (P < 0.05). On the other hand, plant available phosphorus or potassium and microbial biomass carbon (C) in the soil were neither significantly affected by any application rate of ZNPs nor zeolite mixed AS. Soil microbial biomass N was significantly higher in second and third application rates of both ZNPs and zeolite amended AS treatments compared to AS alone. However, this increment in mineral N did not influence shoot uptake and herbage apparent recovery of this nutrient from AS. Similarly, co-mixing of both ZNPs and zeolite in AS did not influence shoot N uptake but Zn uptake was significantly higher in this treatment compared to AS alone. Therefore, this combination would be considered for improving crop Zn uptake under such fertilizer management regimes.