ABSTRACT
Integrated Soil Fertility Management (ISFM) is the application of soil fertility management principles and the knowledge to adapt these to local conditions which optimizes fertilizer and organic resource use efficiency and crop productivity. These practices necessarily include proper fertilizer and organic input management in combination with the utilization of germplasm. The objective of the study was determined the effects of the combined application of inorganic N fertilizer with manures and the maize-legume cropping systems on the fertility and crop productivity of smallholder farms. The study consisted of three experiments; a fertilizer-manure combination experiment, a maize-legume cropping systems experiment and an N response experiment. The treatments consisted of five levels of inorganic N fertilizer (0, 30, 60, 90.and 120 kg N ha-1)each combined with 2.5 t ha-1 sheep and goat manure except the zero, five maize legume cropping systems; soybean-maize rotation plus cowpea relay (SBMZRT), groundnut-maize rotation plus cowpea relay (GNMZRT), soybean/maize strip cropping (SBMZSP), groundnut/maize strip (GNMZSP) and a continuous maize cowpea intercrop (CTMZCPInt), and five levels of inorganic N fertilizer (0, 30, 60, 90.and 120 kg N ha-1). The treatments were laid out in a randomized complete block design (RCBD) and replicated four times. The experiments were carried out in 2012 and 2013, and repeated on three smallholder farms in Pampaida, Saulawa and Fulani Sule in Ikara Kaduna northern Guinea savanna Nigeria. The results showed that compared with sole fertilizer, combined application of inorganic fertilizer with sheep and goat manure significantly increased nutrient uptake (45.74 and 71.09 kg ha-1 respectively), grain yield (2.89 and 5.58 t ha-1 respectively), both of which increased with increasing N-levels, and AEN (18.38 and 51.07 kg kg-1 respectively) which decreased with increasing N levels. SBMZRT, on the other hand, gave the highest grain yield (6.96 t ha-1), nutrient uptake (111.58 ix kg ha-1) and AEN (63.74 kg kg-1) even though they did not differ significantly from the other maize-legume systems except the CTMZCPint which gave the lowest values (3.23 t ha-1, 40.66 kg ha-1 and 16.5 kg kg-1 respectively). Application of 90 kg N ha-1 when combined with 2.5 t ha-1 sheep and goat manure resulted in significantly higher SMBN (21.67 mg kg-1) and lowest C/N ratio (7.25), while 120 kg N ha-1 gave the highest SMBC in the same scenario but did not significantly differ with 90 kg N ha-1 when compared with other N levels. Combined application of inorganic fertilizer with sheep and goat manure proved to be more profitable (VCR = 3.06) than the sole fertilizer application (VCR =1.9).maize rotation with legumes are more profitable, returning higher value per unit cost invested than maize/legume strip cropping. There was however no significant difference between them, and they were all significantly better than the continuous maize cowpea relay. The information obtained indicates that AEN is amenable to improved management practices and that the various components of the ISFM results in improvement of AEN, grain yield and nutrient uptake of maize. These options also gave high soil microbial biomass as well as represented economically profitable alternatives for smallholder farmers.
