Pulp and paper mill sludges are produced from primary and secondary treatment of wastes derived from virgin wood fiber sources, recycled paper products, and non-wood fibers. Sludges and sludge composts may be utilized in agriculture to increase soil organic matter, improve soil physical properties, provide nutrients, and increase soil pH. Positive effects of primary, deinking, and low-nutrient combined sludges on soil quality are primarily due to increased soil organic matter, aggregation, water holding capacity, infiltration rate, and cation exchange capacity. Nitrogen and P immobilization are often induced by primary and deinking sludges, but can be overcome by delayed planting, adding N and P, planting of legumes, or composting. Improved crop production obtained with secondary treatment sludges is most often attributable to enhanced nutrient availability, particularly N, but improved soil physical properties are implicated in some studies. Pulp and paper mill sludges and sludge composts are useful soil amendments and plant nutrient sources. Key words: Paper mill sludge, soil physical properties, N and P immobilization, nutrient efficiency, land application

The development of cropping systems that use N efficiently requires methods that evaluate system differences in N use. A procedure, based conceptually on soil and plant processes that affect N use, was developed to evaluate differences in N use efficiency among cropping systems. The method uses measurements of yield, grain N, aboveground plant N, applied N, and postharvest inorganic soil N to partition cropping system differences in yield and grain N into N efficiency components. The components consist of N supply, available N efficiency, available N uptake efficiency, N utilization efficiency, grain Naccumulation efficiency, and N harvest index. The N efficiency component analysis was demonstrated for a field study with hard red spring wheat (Triticum aestivum L. ‘WB 906R’) where conventional tillage had a greater yield and grain N than no‐tillage. At low N rates, 78% of the difference in yield between the two was attributed to N supply and available N efficiency components. At high levels of applied N, 88% of the yield difference was attributed to the N utilization efficiency component. Differences in grain N were attributed to N supply and available N efficiency components, whereas components of grain N accumulation efficiency, available N uptake efficiency, and N harvest index were nonsignificant. Overall, this new approach transcends empirical analyses and provides insight into underlying mechanisms of cropping system differences in N use.

Nitrogen use efficiency (grain weight per unit of N supplied from soil or fertilizer) can be reduced by overfertilization, suboptimal yields, and N losses. Nitrogen is typically fall‐applied in eastern Washington for soft white winter wheat (Triticum aestivum L.) production, and is therefore subject to overwinter losses or accumulation in deep soil layers. Increasing grain protein levels of soft white winter wheat have been attributed in part to excessive N application rates and high residual N levels. Spring N applications were evaluated over four site‐years as an option to all‐fall applied N for reducing N inputs and improving N use efficiency, thereby allowing producers to maintain productivity while controlling grain protein. Five to six N rates ranging from 0 to 140 kg ha−1 for the all‐fall N applications were compared with fall‐spring split applications of 84 to 140 kg total N ha−1. Nitrogen was applied in the spring by topdressing (TD) or with a spoke‐wheel point‐injection (PI) system. A 15N experiment was conducted at two locations during the second year to quantify N uptake from fertilizer and soil N. High preplant residual N conditions resulted in limited responses to added N. Nitrogen use efficiency was 26 to 44% lower in the 140 kg ha−1 fall‐applied N treatments than in the zero‐N control. Reduced N use was related to N losses from the system and to decreased N utilization efficiency (grain weight produced per unit plant N). Spring‐applied N, with point injection or topdressing, maintained or increased N use efficiency compared with equivalent all‐fall N rates of 84 and 112 kg N ha−1. More 15N‐labeled fertilizer (7–16% more) was recovered with a split N application than with fall‐applied N at the same total rate of 112 kg N ha−1. At maturity, 68% of plant N was from soil sources with a split application, compared with 80% with an all‐fall application. These results suggest spring‐N applications with point injection or topdressing can improve fertilizer N recovery and N use efficiency over preplant applications in dryland winter wheat.

if (i) sufficient heat units are available to promote cover crop growth, root exploration, and N uptake during fall and winter; and (ii) mineralization rates of the green-Overwinter N leaching increases the potential for NO 3 contamination of ground water under irrigated desert soils. Our objectives were manured residues in the spring coincide with the timing to (i) identify winter cover crops for recovering N and (ii) determine of cash crop N demand. Effective fall-sown cover crops the N availability following green manure cover crops relative to N should exhibit rapid germination, aggressive and extenuptake by a succeeding potato (Solanum tuberosum L.) crop. A 2-yr sive rooting systems (Sainju et al., 1998), good winter field study was conducted on commercial fields on Quincy loamy hardiness, and early spring regrowth. Cereal and brassand (mixed mesic Xeric Torripsamments). Cover crops were seeded sica crops display these characteristics and are well following sweet corn (Zea mays L.) as fall-incorporated sudangrass suited for winter cover cropping (Wagger and Mengel, (Sorghum bicolor L., 'Sordan'); fall-and spring-incorporated white 1988; Brinsfield and Staver, 1991). These cover crops mustard (Brassica hirta Moench, 'Martegena'); and spring-incorpocan accumulate up to 150 kg N ha Ϫ1 (Hoyt and Mikrated wheat (Triticum aestivum L., 'Stevens'), rapeseed (B. napus kelsen, 1991; Shennan, 1992; Ditsch et al., 1993), with L., 'Jupiter'), and rye (Secale cereale L.). Potato ('Russet Burbank') was planted 3 to 5 wk after spring incorporation of green manures. rooting systems reaching depths of between 80 and 150All cover crops except sudangrass accumulated 112 to 142 kg N ha Ϫ1 cm Sarrantonio, 1992). when planted in August at Plymouth, WA, but N uptake was de-Following green manure incorporation, cover crops creased by Ͼ50% when planted in September at Quincy, WA. Overmay supply 20 to 55% of the recovered N to the subsewintering cover crops lowered soil mineral N at 0 to 180 cm by 155 quent crop (Sims and Slinkard, 1991; Malpassi et al., kg N ha Ϫ1 compared with bare fallow at Plymouth. Fall-incorporated 2000). Subsequent fertilizer requirements can be greatly mustard released greater inorganic N over the winter compared with reduced or eliminated (Griffin et al., 2000) if N release is spring incorporation. Soil NH 4 and NO 3 increased following overwinsynchronized with N demand of the succeeding summer tering cover crops by potato planting, providing timely increases in crop (Stute and Posner, 1995). Poor synchronization N availability to the potato crop. Winter cover crops can improve N or delays in N mineralization of cover crop residue, cycling and reduce the amount of N below the root zone in potatobased rotations.

Winter wheat (Triticum aestivum L.) yield varies greatly among landscape positions in the Palouse region of eastern Washington, yet N fertilizer is typically applied uniformly. Varying N fertilizer rates within fields to match site‐specific N requirements can increase fertilizer use efficiency; however, spatially variable N management programs are limited by their ability to predict site‐specific yield potentials and the resultant N requirements. The objective of this study was to ascertain the role of yield components and soil properties in determining soft white winter wheat grain yield and protein when N application rates are varied among landscape positions. Nitrogen fertilizer (0 to 140 kg N ha−1) was fall‐applied on footslope, south‐backslope, shoulder, and north‐backslope landscape positions at each of two farms in 1989 and in 1990. Grain yield among landscapes varied by up to 55% in 1990 and by up to 33% in 1991. Landscape position grain yields increased by 199 kg ha−1/(cm precipitation + soil water reduction) (r2 = 0.51) and by 706 kg ha−1 per 100 spikes m‐2 (r2 = 0.76). Grain protein concentration among landscapes increased by 2.7 g kg−1 per each increase of 10 kg residual soil NO3−N ha−1 (r2 = 0.82). The large differences in grain yield among landscape positions may justify spatially variable N application. Improved N management should favorably reduce soft white winter wheat protein concentrations by minimizing high residual N levels as well as improve net returns and reduce environmental degradation. The basis for this improved N management may be site‐specific yield estimates calculated from soil water availability and spike density.